JPH08144843A - Body structure of large type two cycle engine - Google Patents

Abstract

PURPOSE: To control the deformation of a bed plate at a top dead center or a bottom dead center of a piston by arranging each one piece of tiebolts for fastening the bed plate and a jacket on a crankshaft journal between cylinder centers, in front of a front end cylinder and at the back of a rear end cylinder. CONSTITUTION: In the body structure of a large type two cycle engine composed by fastening a bed plate 1, an engine frame 2 and a jacket 3 with tiebolts 4, each one piece (in the case of four cylinders, five pieces in total) of tiebolts 4 is arranged on each main bearing located between the centers of cylinders and before and behind the cylinders from the jacket 3 through the engine frame 2. A nut 5 is threadedly engaged with the upper end of each tie bolt 4, and its lower part is joined to a main bearing cap 7. In the case where the fastening force of each tie bolt 4 is transmitted to the bed plate 1, since its acting point approaches the lateral center of the engine, and a distance between the above acting point and the acting points of gas pressure in the cylinder at the top and the bottom dead center of the piston and of the inertia force becomes shorter, the deformation of the bed plate can be restrained to be small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the body structure of a large two-stroke engine.

[0002]

2. Description of the Related Art The body structure of a large-sized two-cycle engine of a conventional example will be described with reference to FIG. FIG. 2 is a perspective view of a main body structure of a large-sized two-cycle engine of a conventional example, which is a four-cylinder engine. In the figure, 1a is the bottom of the base plate, and 2
a is a frame and is mounted on the base plate 1a, 3a is a jacket and is mounted on the frame 2a, and 4a is tie bolts between the cylinders and before and after the front end cylinder and after the rear end cylinder.
Through the base plate 1a, the frame 2a, and the jacket 3a, a nut 5a is placed on the upper side and a nut 6a is placed on the lower side to tighten the book. Reference numeral 9a is a crankshaft, and a flywheel 10a is fixed to the end thereof, and there are five journal portions.

The operation of the conventional example will be described. The tie bolt 4a is tightened with a predetermined initial tightening force by a nut 5a and a nut 6a through a base plate 1a, a frame 2a and a jacket 3a. Even if the cylinder internal pressure becomes high, a compressive force is applied between the base plate 1a, the frame 2a and the jacket 3a. Acts to keep the average stress level of the base plate 1a, the frame 2a, and the jacket 3a at the portion with large fluctuating stress on the negative side.

[0004]

In the conventional structure, two tie bolts are arranged between the centers of the cylinders, in front of the front end cylinder and in the rear of the rear end cylinder, which are distributed on both sides of the crankshaft. ing. For this reason, especially when considering the base plate, the point of application of the tightening force of the tie bolts also deviates from the center in the left-right direction of the engine. On the other hand, the load due to the in-cylinder pressure or the inertial force load due to the motion of the piston, connecting rod, etc. acts on the center in the left-right direction of the engine from the crankshaft journal.
There is a problem that the deformation of the base plate increases due to the deviation from the point of application of the tie bolt tightening force.

An object of the present invention is to solve the above-mentioned problems and provide a highly reliable large-sized two-cycle engine main body structure with small deformation even at high output.

[0006]

A body structure of a large two-cycle engine according to a first aspect of the present invention is a body structure of a large two-cycle engine in which a base plate, a frame and a jacket are fastened with tie bolts 4, wherein the tie bolts are One of each is arranged on the crankshaft journal between the centers of the cylinders, in front of the front end cylinder and behind the rear end cylinder, and the lower end of the tie bolt is connected to the main bearing cap 7.

A main body structure of a large two-cycle engine according to a second aspect of the present invention is the main body structure of a large two-cycle engine in which a base plate, a frame and a jacket are fastened with tie bolts 4, wherein the tie bolts are located between the centers of the cylinders and at the front end. Two cylinders are provided on each of the crankshaft 9 journals at the front of the cylinder and at the rear of the rear end cylinder, and the lower ends of the tie bolts are connected to the main bearing cap 7.

[0008]

Since the first invention is constructed as described above,
Since the tie bolt tightening force is transmitted to the base plate through the main bearing cap and cap bolt, its action point approaches the center in the left-right direction of the engine and the action point of gas pressure load or inertial force load at the top dead center or bottom dead center of the piston. The distance between and becomes small, and the deformation of the base plate becomes small. In the second invention, in addition to the operation of the first invention, since the number of tie bolts is doubled, the bolt diameter becomes smaller, the cylinder center distance is reduced, and the engine overall length can be shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the first invention will be described with reference to FIG. FIG. 1 is a perspective view of a first embodiment according to the present invention, in which 1 is a base plate at the bottom, 2 is a frame on the base plate 1, and 3 is a jacket on the frame 2. The glue 4 is a tie bolt, one from the jacket 3 through the frame 2 and one on each main bearing between the centers of the cylinders and in the front and rear,
Since there are four cylinders, a total of five are arranged, the nut 5 is attached on the upper side, and the lower side is connected to the main bearing cap 7. 8
Attaches the main bearing cap 7 to the base plate 1 with a cap bolt.

The operation of the first embodiment will be described. The tightening force of the tie bolt 4 is the main bearing cap 7, the cap bolt 8
Since it is transmitted to the base plate 1 through the base plate 1, the working point approaches the center in the left-right direction of the engine, and the distance between the cylinder gas pressure or the inertial working point at the top dead center or the bottom dead center of the piston becomes small. The deformation of the base plate 1 is reduced.

In a second embodiment according to the second invention, the first
In the case of the first embodiment according to the first invention in addition to the operation of the invention,
Since the number of tie bolts 4 is one for each main bearing, the number of tie bolts 4 is two, so that the tie bolts 4 are thin, the cylinder center distance is reduced, and the effect of shortening the overall length of the engine is added.

[0012]

Since the first aspect of the present invention is configured as described above and operates as described above, the deformation of the base plate at the top dead center or the bottom dead center of the piston is small, and thus the fluctuation stress due to the deformation of the base plate is small. As a result, high reliability can be secured even at high output.

In addition to the effect of the first aspect of the invention, the second aspect of the invention has the additional effect that the center distance of the cylinders is reduced and the overall length of the engine is reduced because the tie bolts are made thinner.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment according to the present invention.

FIG. 2 is a perspective view of a second embodiment according to the present invention.

FIG. 3 is a perspective view of a conventional example.

[Explanation of symbols]

1 ... Base plate, 2 ... Frame, 3 ... Jacket, 4 ... Tie bolt, 5 ... Nut, 6 ... Nut, 7 ... Main bearing cap, 8
… Cap bolts, 9… Crankshafts, 10… Flywheels.

Claims (2)

[Claims] 1. A main structure of a large two-cycle engine comprising a base plate, a frame and a jacket fastened with tie bolts (4), wherein the tie bolts are located between the centers of the cylinders, the cranks in front of the front cylinder and behind the rear cylinder. A main structure of a large-sized two-cycle engine, characterized in that each one is arranged on a journal of a shaft (9), and a lower end of the tie bolt (4) is connected to a main bearing cap (7). 2. A main body structure of a large two-cycle engine in which a base plate, a frame and a jacket are fastened with tie bolts, wherein the tie bolts (4) are located between the centers of the cylinders, cranks in front of the front end cylinder and behind the rear end cylinder. The main structure of a large-sized two-cycle engine, wherein two tie bolts (4) are arranged on each journal (9) and a lower end of each tie bolt (4) is connected to a main bearing cap (7).