JP2595869B2 - Diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a small diesel engine of NO _x occurs.

[0002]

2. Description of the Related Art In a conventional diesel engine, FIG.
As shown in (1), the center C of the crankshaft was disposed on the center axis L of the piston (or the center axis of the liner). When the crankshaft rotates, the piston P operates as shown in FIG. 5, and a cylinder pressure corresponding to this operation is realized as shown in FIG. Then, if fuel is injected at a predetermined timing as shown in FIG. 6, initial combustion occurs after ignition delay and continues to main combustion.

[0003]

According to the above-described combustion process in the conventional diesel engine, the fuel injected at the time of ignition delay burns at once in the initial combustion and dP / dθ (P
Is the pressure in the cylinder, and θ is the crank angle), which causes a problem that the generation of NO _x increases.

[0004] The present invention, pressing the way up of the initial combustion by reducing the ignition delay in a diesel engine, which aims to reduce the occurrence of NO _x.

[0005]

SUMMARY OF THE INVENTION In the diesel engine of the present invention, the rotation direction of the crankshaft is viewed clockwise so that the inclination angle of the connecting rod with respect to the center axis of the piston becomes larger when the piston is lowered than when it is raised. The center of the crankshaft is set at a position of 25 mm to 50 mm on the right side of the center axis of the piston.

[0006]

In the diesel engine of the present invention, the piston rises faster than the diesel engine in which the center of the crankshaft is located on the center axis of the piston, and the rising speed of the piston gradually decreases near the ignition timing. . As a result, the compression pressure increases rapidly, the compression temperature increases,
Since it can be held for a long time, the ignition delay time is reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In the diesel engine according to the present embodiment, as shown in FIG. 1, the center C of the crankshaft is set at a position deviated from the center axis L of the piston by an offset amount A. The direction to offset the center C of this crankshaft is
When the rotation direction of the crankshaft is viewed as clockwise as shown in FIG. 1, it is on the right side with respect to the center axis L of the piston P.

By offsetting the center C of the crankshaft to this position, the inclination angle of the connecting rod B with respect to the center axis L of the piston P is larger when the piston P is lowered than when it is raised. Therefore, as can be seen from the amount of movement of the piston shown in FIG.
The piston approaches the top dead center earlier than in the case where there is no offset, and approaches slowly during the subsequent compression (crank angle -80 ° to −0 °). In addition, as shown in FIG.
The ascending speed of the piston at the time of compression near 0 ° is faster than that without offset, and the crank angle is -8.
The rising speed of the piston during compression near 0 ° to 0 ° gradually decreases.

For this reason, at the beginning of the compression stroke (crank angle of about -180 ° to about -80 °), the ascending speed is large, and the inside of the cylinder rapidly rises to high temperature and high pressure. In other words, the high-temperature high-pressure state can be maintained for a longer time, so that the ignition delay time after fuel injection is reduced. Then, as the ignition delay is shortened, the amount of fuel injected during that time is reduced, explosive combustion after the ignition delay is suppressed, and the amount of generated NO _X is reduced. According to the present embodiment, the conventional ignition delay of 1 to 3 msec (several degrees in crank angle) can be reduced by 20 to 30% by offsetting the center C of the crankshaft by 25 to 50 mm. And whereby the occurrence of the NO _X can be reduced 20-30%.

[0010]

According to the present invention, the center of the crankshaft is set on the right side of the center axis of the piston when the rotation axis of the crankshaft is viewed clockwise. The rising speed is large, the inside of the cylinder rapidly becomes high temperature and high pressure, and the rising speed becomes slow immediately before fuel injection, and the high temperature and high pressure state can be maintained longer, so that the ignition delay after fuel injection can be shortened, NO _X
Can be reduced.

[Brief description of the drawings]

FIG. 1 is a view showing a drive mechanism of a crankshaft according to an embodiment of the present invention.

FIG. 2 is a graph comparing a conventional example and the present embodiment with respect to a relationship between a crank angle and a piston movement amount.

FIG. 3 shows a relationship between a crank angle and a piston speed.
9 is a graph comparing a conventional example with the present embodiment.

FIG. 4 is a diagram showing a drive mechanism of a crankshaft in a conventional diesel engine.

FIG. 5 is a graph showing a relationship between a crank angle and a piston position in a conventional diesel engine.

FIG. 6 is a graph showing a combustion state in a conventional diesel engine.

[Explanation of symbols]

 P Piston B Connecting rod C Center of crankshaft L Center axis of piston

Claims (1)

(57) [Claims] When the rotation direction of the crankshaft is clockwise, the angle of inclination of the connecting rod with respect to the center axis of the piston becomes larger when the piston is lowered than when it is raised . A diesel engine characterized by setting the center of the crankshaft at the position .