JPH08226432A - Crank shaft - Google Patents

Abstract

PURPOSE: To reduce the stress of a bearing metal and improve reliability of a bearing by reducing bearing reaction by the torsional torque of a crank shaft. CONSTITUTION: An I-shaped cross section part 12 whose cross section at right angles to a crank slow center line 10 for connecting the center of a crank pin 3 with that of a journal 1 consists of both the ends 12a of a thick wall and the middle part 12b which connects them and has a thinner wall than it is formed at a crank web 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating internal combustion engine, a reciprocating compressor crankshaft, and the like.

[0002]

2. Description of the Related Art An example of a conventional crankshaft for a large marine diesel engine is shown in FIG. This crankshaft 100
Comprises a crank pin 3 to which connecting rods of pistons fitted in seven cylinders are connected, and a crank web 2 connecting these crank pins 3 to a journal 1.
Each journal 1 is supported by a bearing (not shown).

During operation of the diesel engine, each cylinder
The explosion pressure inside is transmitted to each crank pin 3 through the connecting rod in a predetermined order, and is transmitted to the journal 1 through the crank web 2 to generate a torsion torque around the axis 4. The torsional torque rotationally drives the propeller shaft (not shown) connected to the shaft end flange 5 of the crankshaft 100.

[0004]

In the above crankshaft 100, as shown in the schematic diagram of FIG. 3, the journal 1 is formed by twisting the crank pin 3 and bending the crank web 2 based on the twisting torque around the shaft core 4. Misaligned with the axis 4
On the other hand, since each journal 1 is bundled by the bearing, a bearing reaction force F for pushing back the displacement e of the shaft core 4 is generated in each journal 1.

The magnitude of the bearing reaction force F is comparable to the bearing load due to the explosion pressure or the bearing load due to the inertial force generated by the movement of the piston, the connecting rod, etc.
In addition to the above bearing load, the bearing reaction force F is applied to the bearing. Therefore, there is a problem that the stress of the bearing metal of the bearing becomes excessively large, causing abnormal wear and seizure, which lowers the reliability of the bearing.

It is an object of the present invention to reduce the reaction force of the bearing to maintain the strength of the crankshaft and reduce the stress of the bearing metal to improve the reliability of the bearing.

[0007]

SUMMARY OF THE INVENTION The present invention has been invented to solve the above problems, and its gist is to provide an internal combustion engine having a crank web for connecting a crank pin to a journal, and a reciprocating engine. In a crankshaft for a reciprocating engine such as a dynamic compressor, a cross-sectional shape perpendicular to the crank throw center line connecting the center of the crank pin and the center of the journal to the crank web connects the both ends with thick wall The crankshaft is also characterized in that an I-shaped cross section forming an I-shape is formed by a thin middle portion.

Another feature is that the I-shaped cross section is formed over substantially the entire length of the crank web.

Another feature is that the crank webs of all the crank throws are formed with the above I-shaped cross section.

[0010]

In the present invention, since the thin intermediate portion of the I-shaped cross section is close to the neutral surface for bending due to the torsional torque around the journal axis, the torsional rigidity of the crank web is hardly reduced. Is greatly reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A crankshaft for a large marine diesel engine according to an embodiment of the present invention is shown in FIG. 1, (A) is a front view and (B) is a crankshaft.
6A is a sectional view taken along the line BB of FIG. 7A, and FIG. 8C is a sectional view taken along the line CC of FIG.

The crankshaft 100 is for seven cylinders. The seven crankpins 3 to which the connecting rods 3 of the pistons fitted in the respective cylinders are connected, and the crank web 2 for connecting these crankpins 3 to the journal 1. It is equipped with
The journals 1 are each supported by bearings and have shaft ends 5
A propeller shaft is connected to.

As shown in FIG. 1B, the crank web 2 has thick cross-sections 12a having a cross-sectional shape perpendicular to the crank throw center line 10 connecting the center 6 of the crank pin 3 and the center 4 of the journal 1. An I-shaped cross section 12 having an I-shape is formed by a thin intermediate portion 12b connecting the both end portions 12a, 12a.

As shown in FIG. 1C, the I-shaped cross section 12 is formed over the substantially entire length of the crank web 2 from the upper edge of the journal 1 to the lower edge of the crank pin 3.

During operation of a large marine diesel engine, a torsional torque is generated around the axis 4 of the journal 1 due to the explosion pressure in the cylinder, and the deviation e of the axis 4 due to the torsional torque causes the twisting of the crank pin 3 and the crank web. Since the displacement e occurs due to the bending of No. 2, the larger the torsional rigidity of the crank pin 3 and the greater the bending rigidity of the crank web 2, the smaller the deviation e becomes.

On the other hand, since the bearing reaction force F that pushes back this deviation e is generated mainly by twisting the crank web 2, the bearing reaction force F with respect to the deviation e of the same magnitude becomes smaller as the torsional rigidity of the crank web 2 decreases. Get smaller. That is, the bearing reaction force F based on the torsional torque becomes smaller as the bending rigidity of the crank web 2 becomes larger and as the torsional rigidity becomes smaller.

In the crankshaft 100, however, the thin intermediate portion 12b of the I-shaped section 12 is close to the neutral plane of bending due to the torsional torque around the journal axis 4,
The bending rigidity of the crank web 2 is hardly reduced as compared with the conventional crank web having a rectangular cross section, but the torsional rigidity is significantly reduced. Therefore, the bearing reaction force due to the torsion torque is reduced, and the bearing load is reduced.

Particularly, since a large marine diesel engine is a so-called long stroke type in which the ratio of piston stroke to cylinder diameter is large, the length of the crank web 2 is set to the crank pin 3.
Is sufficiently large relative to the diameter of the journal 1 or the diameter of the journal 1, so that the crank web 2 can be formed with an I-shaped cross section 12 having a sufficient length. Therefore, in such a diesel engine, the effect of reducing the torsional rigidity of the crank web 2 becomes greater.

[0019]

According to the present invention, the crank web has a thick cross section perpendicular to the center line of the crank throw connecting the center of the crank pin and the center of the journal, and the both ends which are thicker than the both ends and which are intermediate in thickness. Since the I-shaped cross section forming the I-shape is formed, it is possible to reduce the torsional rigidity of the crank web without reducing the bending rigidity thereof.

As a result, the bearing reaction force based on the torsion torque can be reduced, so that seizure and abnormal wear of the bearing metal can be prevented by the reduction of the surface pressure of the bearing metal, and the durability of the bearing metal can be improved. Improves reliability.

If the I-shaped section is formed on the crank web over substantially the entire length thereof and / or the I-section is formed on the crank webs of all the crank throws, the effect due to the reduction of the torsional rigidity becomes greater.

[Brief description of drawings]

1 shows a crankshaft for a large marine diesel engine according to an embodiment of the present invention, (A) is a front view, (B) is a sectional view taken along line BB of (A), and (C) is It is sectional drawing which follows CC line of (A).

2 shows a conventional crankshaft, (A) is a front view, (B)
FIG. 7A is a sectional view taken along line BB in (A).

FIG. 3 is a schematic view showing a bent and deformed state of a conventional crankshaft.

[Explanation of symbols]

 100 crank shaft 1 journal 2 crank web 3 crank pin 4 journal shaft core 12 I-shaped cross section 12a both ends 12b middle part 10 crank throw center

Claims (3)

[Claims] 1. A crankshaft for a reciprocating engine such as an internal combustion engine or a reciprocating compressor, comprising a crank web for connecting a crank pin to a journal, wherein the crank web connects the center of the crank pin and the center of the journal to the crank web. A crankshaft, characterized in that an I-shaped cross section having an I-shaped cross-section perpendicular to the throw center line is formed of both ends having a thick wall and an intermediate part having a thickness thinner than this connecting these ends. 2. The I-shaped cross section is formed on the crank web over substantially the entire length thereof.
The indicated crankshaft. 3. The I-shaped cross section is formed in the crank webs of all crank throws.
The indicated crankshaft.