JPS63167074A - Four cycle v-type two cylinder engine - Google Patents

Abstract

PURPOSE:To make only one installed decompression device sufficiently serve an engine to reduce the number of parts of the engine and its production cost by providing the decompression device for only one cylinder having a piston proceeding into compression stroke as the piston in another cylinder is made to move to a top dead center. CONSTITUTION:When an engine 30 starts to counterclockwise rotate a crankshaft 25, each of pistons 19, 20 in front and rear cylinders 3, 5 repeats in order each of combustion, exhaust, intake end compression strokes according to an increase in a crankangle. In this case, when the piston 19 is at a crank rotating angle toward the compression stroke, the piston 20 is in the exhaust stroke, and when the piston 20 is at the crank rotating angle toward the compression stroke, the piston 19 is in the combustion stroke. Thus for the restart of the engine 30, only compression pressure in the front cylinder 3 may be temporarily reduced by a decompression device 1 to shift the piston 19 to the combustion stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-stroke two-cylinder engine, and particularly to a two-cylinder V-type engine mounted on a motorcycle.

[Prior art]

Conventionally, a V-type two-cylinder engine mounted on a motorcycle is equipped with a decompression device that temporarily removes the compression pressure in the cylinder in order to make it easier to start the engine.

FIG. 6 is a cross-sectional view of a main part showing a conventional V-type two-cylinder engine (hereinafter simply referred to as the engine) 2 equipped with the above-mentioned decompression device 1. In particular, the included cylinder angle θA is
0'), a so-called narrow angle V-type engine is shown.

In this engine 2, a cylinder head 4 of a front cylinder 3 disposed at the front with respect to a vehicle body frame (not shown), and a cylinder head 6 of a rear cylinder 7 disposed at the rear
A decompression device 1 is installed inside each of the two.

This decompression device 1 includes a rocker arm 9, which drives an exhaust valve 7.8 disposed at a 4° 6 end of each cylinder.
It consists of a decompression camshaft 11 provided at 10, an arm 12 fixed to this camshaft 11, and a decompression cable 13 that drives this arm 12,
One end of each decompression cable 13 is connected to a decompression solenoid 14, respectively. Note that this decompression solenoid 14 operates based on a drive signal from a control circuit (not shown).

According to such a decompression device 1, each cylinder 3,
←During the compression process at the start of the 76, the respective decompression devices 1 are operated to move the exhaust pulp 78 downward by the decompression camshaft 11 to temporarily reduce the compression pressure. When the compressor is released, the compression pressure is reduced and the engine 2 can be started easily.

In FIG. 6, reference numerals 15 and 16 are rocker arms that drive intake valves 17 and 18, respectively, and 19 and 20 are pistons disposed inside the front cylinder 3 and rear cylinder 5, respectively. The crank pins 23 and 24 supporting the connecting rods 21 and 22 of the crankshafts 25 and 20 are mounted with the crankshaft 25 as the center &δ and shifted in phase by &x.

By the way, according to the conventional engine 2 described above, in order to easily start the engine, the decompression devices 1 must be installed at two locations on each of the front and rear cylinder rads 4 and 5.
The problem was that the structure was complex and the number of parts was large.

[Purpose of the invention]

In view of the above-mentioned problems, the present invention provides a 4-cycle/I/V type two-cylinder engine that has a simple structure and a small number of parts.

[Structure of the invention]

In order to achieve the above-mentioned object, this invention arranges a piston that moves toward the compression process while moving the piston located in one of the two cylinders of a four-stroke V-type two-cylinder engine to the top dead center. A decompression device is installed only on the other cylinder.

〔Example〕

Fig. 1 shows a 4-cycle type two-cylinder engine 3 according to the present invention.
0 (hereinafter simply referred to as the engine), and the same parts as in FIG. 6 are designated by the same reference numerals.

In this engine 30, the decompression device 1 is disposed only in the cylinder head 4 of the front cylinder block, and this single decompression device 1 is used to control the compression process of the piston 19 housed in the front cylinder 3. , the compression pressure is temporarily released to decompress the engine 30.

Next, the effect will be explained. Figure 2 shows the crankshaft 25
The conceptual diagram of FIG. 1 shows the positional relationship of each piston 19, 20 with respect to the rotation angle (crank rotation angle) θ of This figure shows a state in which the position of the crank bin 23 is defined as the initial position, that is, the crank rotation angle O0.

When the engine 30 starts and the crankshaft 25 rotates counterclockwise from the initial position shown in FIG. 2, the piston 19 of the front cylinder 3 and the piston 20 of the rear cylinder 5 move 5K as shown in the graph of FIG. The combustion, exhaust, intake, and compression processes can be repeated in sequence as the crank rotation angle (θ) increases. In FIG. 3, symbol 0 is a crank rotation angle indicating the top dead center of each piston, and X is a rotation angle indicating the bottom dead center of each piston. When the ignition of the engine 3o is stopped in such an operating state of the engine 30, the engine 3o
In this case, the rotation continues due to the inertia of the crankshaft 25, and then stops when one of the pistons reaches the compression stroke. That is, the engine 30 operates when the piston 19 of the front cylinder 3 reaches the compression stroke (at that time, the crank rotation angle θ=iso0+θA+θB), or when the piston 19 of the front cylinder 3 reaches the compression stroke, as shown in FIG. When the piston 2o reaches the compression stroke (at that time, the crank rotation angle θ = 540'
) to stop its rotation. By the way, as shown in Figure 4,
The crank rotation angle θ at which the piston 19 of the front cylinder 3 reaches the compression stroke is θ = 180' + θλ + θB, and the piston 2 of the rear cylinder 5 at this rotation angle
0 is in the exhaust process as shown in FIG. 3, and the piston 20 is in a position of moving toward the top dead center. On the other hand, as shown in FIG. 5, the crank rotation angle θ at which the piston 2o of the rear cylinder 5 reaches the compression stroke is θ=540', and the piston 19 of the front cylinder 3 at this rotation angle
is in the combustion process, and the piston 19 is in a position of moving toward the bottom dead center.

Comparing the rotational force for further rotating the crankshaft 25 counterclockwise from the compression process of each piston 19.20 shown in FIGS. 4 and 5, in FIG. A rotational force T1 is required to simultaneously direct the pistons toward the top dead center, whereas in FIG. 5, the piston 19 of the front cylinder 3 is directed toward the bottom dead center.
It is sufficient that there is at least a rotational force T for directing only the piston 20 of the rear cylinder 5 toward the top dead center.

Therefore, if T becomes >% and the ignition of the engine 300 is stopped, there is an extremely high probability that the engine 30 will stop while the piston 19 of the front cylinder 3 reaches the compression stroke, as shown in FIG. Therefore, when starting the engine 30 again, if only the compression pressure in the front cylinder 3 is temporarily released and the piston 19 reaches the combustion stage, the engine 30 can be easily started from then on by the rotational force of the piston 19. . Therefore, it is sufficient to provide the decompression device 1 only within the cylinder head 4 of the front cylinder 3.

In the above embodiment, a so-called phase crank type V-type two-cylinder engine 30 in which the crank pins 23, 24 supporting each piston 19, 20 are offset has been described, but the present invention is limited to the above embodiment. without any trouble,
The present invention may be applied to a so-called coaxial crank type V-type two-cylinder engine in which each piston 19, 20 is supported by the same crank pin.

〔Effect of the invention〕

As explained above, according to the present invention, 4 cycles/I
/ Since the decompression device that makes it easy to start the V-type 2-cylinder engine only needs to be installed on one cylinder, the structure is simple and the number of parts is reduced, thus providing a 4-stroke V-type 2-cylinder engine at a low cost. You can.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main parts of a 4-cycle V-type two-cylinder engine according to the present invention, FIG. 2 is a conceptual diagram of FIG. 1, FIG. 3 is a diagram showing the operation of the piston, and FIGS. 4 and 5. 1 is a conceptual diagram of a 4-stroke type 2-cylinder engine showing the crank rotational position during the piston compression process. 1... Decompression device, 3.5... Cylinder, 4゜6
...Cylinder head, 19.20...Piston, 3
0...4 cycle V type 2 cylinder engine. Figure 4 Figure 5 Procedures Manual (Method) 1 February 4, 1986

Claims (1)

[Claims] A 4-cycle V-type two-cylinder engine characterized in that a piston moves the piston of one cylinder toward the top dead center and moves toward the compression process, and a decompression device is installed only in the other cylinder.