JPH0242298A - Engine assembly structure and assembly method - Google Patents

Abstract

PURPOSE:To prevent the size of a large end part of a connecting rod from being constrained by the size of a cylinder bore by a method wherein a notch part having width being so wide enough to allow a large end part of a connecting rod to be received in a position shifted in a 90 deg. arc from a position where the large end part is mounted on a crank shaft is formed in a wall part between adjoining bores. CONSTITUTION:A notch part 6 having width W being wide enough to allow a large end part 5a of a connecting rod 5 to be received in a position shifted in a 90 deg. arc from a position where the large end part is mounted on a crank shaft 3 is formed in a wall part between the adjoining bores of cylinder bores 1a-1d. When transition in a 90 deg. arc of the connecting rod 5 is made and the large end part 5a is introduced in the notch part 6, a small end part 5b of the connecting rod 5 is protruded through the cylinder bores 1a-1d toward the cylinder head side. With this state, a piston 8 is inserted in the cylinder bore, and the piston 8 is coupled to the small end part 5b of the connecting rod 5 by means of a piston pin 7.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an engine assembly structure and assembly method for an in-line multi-air engine.

[Conventional technology]

In this type of in-line multi-cylinder engine, the piston is inserted into the cylinder bore from the crankcase deck surface with the piston assembled to the connecting rod via the piston pin, and then the large end of the connecting rod is assembled to the crankshaft. The assembly structure and assembly method is adopted. However, recently, due to the smaller size and higher output of engines,
There is a trend to shorten engine length (crankshaft length), and the diameter of each bore in the cylinder block is designed to be as small as possible. Therefore, in order to secure the necessary displacement, the piston stroke must necessarily be lengthened. Therefore, in order to secure an area in which the large end of the connecting rod can move, measures have been taken to form relief grooves on the cylinder block side 1, for example, at the lower end of the cylinder liner, in order to avoid interference with the large end. (Unexamined Japanese Patent Publication No. 61-19
(See Publication No. 2841).

[Problem to be solved by the invention]

The problem here is that if the diameter of the cylinder bore is small and the piston stroke within the cylinder is large, the large end of the connecting rod must be made smaller to avoid interference with the large end. , if the big end is made smaller, the diameter of the crankbin will inevitably be made smaller, and as in the case of a short stroke (see Figure 3), the crankshaft journal b and the crank will be connected to each other via the crank web a. It is no longer possible to ensure the overlap X between the crankshaft journal b and the crankbin C, and instead, as shown in Fig. 4, there is a weak portion y that connects the crankshaft journal b and the crankbin C only with the crank web a. . This goes against the original purpose of increasing the output of the engine. Therefore, as shown in Fig. 5, a design is made in which the diameter of the crank pin C is increased to obtain at least an overlap X' to ensure the strength of the crankshaft. The size of the big end must be ensured. On the other hand, as the diameter of the cylinder bore becomes smaller and the arrangement pitch of the cylinders becomes shorter, the space between the bearings for the crankshaft journal becomes smaller than the above bore diameter, making it impossible to insert the piston into the cylinder bore from the crankcase side. The piston must be inserted into the cylinder bore from the side. At this time, if the large end of the connecting rod is larger than the diameter of the cylinder bore, the assembled piston and connecting rod can be passed through the cylinder bore via the piston pin. become unable. The present invention was made based on the above circumstances, and in order to maintain sufficient rank shaft strength to meet the increase in engine output, the size of the large end of the connecting rod attached to the enlarged crank pin is maintained. However, the piston stroke is long and the pitch of the cylinder arrangement is short,
It is an object of the present invention to provide an engine assembly structure and an assembly method devised so that a piston and a connecting rod can be conveniently assembled even in a cylinder structure with a small cylinder bore.

[Means to solve the problem]

Therefore, in the present invention, in the cylinder bores arranged in parallel in the cylinder block, the wall portion between adjacent bores has a
To attach the large end of the connecting rod to the crankshaft, form a notch with a width that allows the large end of the connecting rod to be installed at a position shifted 90 degrees from the above position, and when the large end of the connecting rod is introduced into the notch, The connecting rod has a small end protruding toward the cylinder head and has a length sufficient to allow the piston pin to be attached to the piston. Further, in the present invention, the connecting rod is inserted from the crankcase side, the assembly to the crankshaft is shifted 90 degrees from the position, the large end of the connecting rod is introduced into the notch formed in the cylinder bore, and in that state. Connect the piston to the small end of the connecting rod that protrudes toward the cylinder head side via a piston pin, return the connecting rod to the crankcase side, and hold the large end of the connecting rod at a 90° angle with the large end led out from the notch. A method has been adopted in which the large end of the connecting rod is connected to the crankshaft.

[For production]

Therefore, when inserting the connecting rod into the cylinder bore from the crankcase side, it can be guided deeply by using the notch in the cylinder bore, and by connecting the piston and the small end of the connecting rod with the piston pin on the cylinder head side. , it was possible to assemble both, and then the connecting rod was returned to the crankcase side and attached to the crank pin, so the crank pin diameter of the crankshaft could be set to a size that would ensure the required strength ( i.e. ensuring overlap between the crank bin and the crankshaft journal via the crank web).

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to FIGS. 1 and 2. In the figure, reference numeral 1 denotes a cylinder block in which cylinder bores 1a to 1d are arranged in parallel, the lower end of which is open at the skirt portion 2 of the crank web, and between the cylinder bores 1a to 1d and the skirt portion 2 ,
A journal bearing 4 is provided that receives a journal 3a of the crankshaft 3. In addition, in order to connect the large end 5a to the crank pin 3b of the crankshaft 3, each cylinder bore 1a is
~1d, as shown in FIG. 1(A), the connecting rod 5
is inserted. The wall portion between adjacent cylinder bores 1a to 1d has a width W for receiving the large end 5a of the connecting rod 5 at a position shifted by 90 degrees from the position where the connecting rod 5 is attached to the crankshaft 3. Notch part 6
is formed, and when the connecting rod 5 is turned 90 degrees as shown in FIG. 1(8) and the large end portion 5a is introduced into the notch portion 6 as shown in FIG. 1(C), The small end 5b of the connecting rod 5 passes through the cylinder bores 1a to 1d and projects toward the cylinder head. In this state, the piston 8 is inserted into the cylinder bore, and the piston 8 is connected to the small end 5b of the connecting rod 5 by the piston pin 7. In this way, the piston 8 is connected to the connecting rod 5 in each of the cylinder bores 1a to 1d, and as shown in FIG. The large end 5a of the connecting rod 5 is attached via the cap 9. In such an assembly structure and assembly method, since the cutout portion 6 on the cylinder side is located in the longitudinal direction of the crankshaft 3, it does not have the same adverse effect on the piston skirt 8a during the operation of the piston 8. Taking into account the operating stroke of the piston ring, the notch portion 6 is formed so that the top of the notch portion 6 is located below the lowest region of the piston ring, with an interval t of, for example, about 3 cities. It would be good if it were done. For this reason, the cutout portion 6
Since the oil does not touch the piston ring, oil from the crankcase side does not wastefully infiltrate between the piston 8 and the liner, thereby preventing an increase in friction. Here, the connection between the piston 8 and the connecting rod 5 is achieved after each piston 8 and the connecting rod 5 are inserted from opposite sides of the cylinder bore, so the size of the large end 5a of the connecting rod 5 is not restricted by the diameter of the cylinder bore. Therefore, in the crankshaft 3, the diameter of the crank pin 3b can be set to such an extent that the overlap between the journal 3a and the crank pin 3b can be ensured via the urchin 13C, and the strength that can support the high output of the engine can be maintained. do. In addition, in order to increase the diameter of the crank pin 3b, the pressure receiving area of the metal of the connecting rod 5 increases and the surface pressure decreases, so the crank pin width is narrowed until the surface pressure can withstand during operation. Since this can be used to increase the thickness of the crank web, the rigidity of the crankshaft 3 can be further improved.

【Effect of the invention】

As described in detail above, the present invention does not restrict the diameter of the large end of the connecting rod by the diameter of the cylinder bore, so it is possible to maintain a sufficient strength of the rank shaft to meet the high output of the engine. Moreover, even in a cylinder structure where the piston stroke is long, the pitch of the cylinder arrangement is short, and the cylinder bore is small, the piston and connecting rod can be conveniently assembled. Therefore, the overall length of the engine can be shortened and downsizing can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing one embodiment of the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Figs. 3 to 5 explain the structural features of the crankshaft. FIG. 1a to 1d...Cylinder bore 3...Crankshaft, 3a...Journal, 3
b...Crank pin, 3C...Web...Journal bearing...Conrod, 5a...Big end,...Notch part...Piston pin...Piston...Cap 5b...・・Small end

Claims (2)

[Claims] (1) In the cylinder bores arranged in parallel in the cylinder block, a notch in the wall between adjacent bores has a width that accommodates the large end of the connecting rod at a position shifted 90 degrees from the mounting position to the crankshaft. and when the large end of the connecting rod is introduced into the notch, the small end of the connecting rod protrudes toward the cylinder head,
An engine assembly structure characterized in that the connecting rod has a length sufficient to allow a piston pin to be attached to the piston. (2) Insert the connecting rod from the crankcase side, rotate it 90 degrees from the assembly position on the crankshaft, introduce the large end of the connecting rod into the notch formed in the cylinder bore, and in this state insert it into the cylinder head side. Connecting a piston to the protruding small end of the connecting rod via a piston pin, returning the connecting rod to the crankcase side, and rotating the connecting rod 90 degrees with the large end led out from the notch, An engine assembly method characterized in that the large end of the connecting rod is connected to a crankshaft.