JP2559971Y2 - 6-cylinder diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an in-line six-cylinder diesel engine, and more particularly to an in-line six-cylinder diesel engine having a reduced dead volume in a combustion chamber during operation. .

[Conventional technology]

Diesel engines are engines that extract explosive energy generated by the fuel sprayed from the injection nozzle ignited by the compression heat before the piston reaches the top dead center while compressing the intake air and reaching the top dead center. It is well known that various measures have been taken to maximize the use of supplied fuel and extract it as output.

As one of the measures, it is required to increase the compression ratio of the air as much as possible. For that purpose, it is required to reduce the waste volume at the time of compression as much as possible. The structure for inserting the piston into the engine cylinder is shown in
It is well-known by the description of -171858 gazette etc. The dead volume will now be described with reference to FIG. In the figure, in a diesel engine 1, a piston 6 is slidably fitted in a cylinder 4 provided in a cylinder block 2. At the top of the piston 6, a concave combustion chamber 8 is provided. FIG. 3 shows a state where the piston 6 has reached the top dead center.

And the piston 6 and is fitted the top ring 10 _0, and the oil ring 10, airtightness between the cylinder 4 and the piston 6, so that mainly kept by the top ring 10 _0. In the figure, 12 is the cylinder head, 14 is the injection nozzle, 16 is the piston pin, and 20 is the suction
It is an exhaust valve.

As shown in FIG. 3, when the piston 6 reaches the top dead center, the internal volume of the cylinder 4 is determined by the air A between the combustion chamber 8 and the cylinder head lower surface 21 and the piston top 22 and the piston 6,
It is given by the sum of the ring-shaped space B defined between the cylinder 4 and the top ring 10 _0. By the way, the compressed air in the combustion chamber 8 is squished by the compression stroke of the piston 6, so that it can be mixed well with the fuel injected from the injection nozzle 14. On the contrary,
The air in the air A and B cannot mix with the fuel. Therefore, it acts as a waste volume that increases the volume after compression and decreases the compression ratio to deteriorate the combustion state.

By the way, the space B needs to be provided with a certain distance so that the piston 6 can slide easily in the cylinder 4.
There is no such limit in the space A. Therefore, conventionally,
The design is made so as to reduce the clearance a between the lower surface of the cylinder head 12 and the top 22 of the piston in consideration of variations in the components, deformation due to thermal expansion of the components during operation, and mechanical deformation.

[Problems to be solved by the invention]

However, the clearance a cannot be reduced to zero due to variations in the dimensions of parts, thermal expansion, dynamic deformation during operation, and the like. In addition, in the case of an in-line six-cylinder diesel engine, the clearance a indicates that the interval during operation is smaller than the interval when the engine is stopped, and that the amount of decrease tends to be constant depending on the position of the cylinder. The inventor has found.

The present invention has been made in view of the above problems and findings, and prevents the gap between the lower surface of the cylinder head and the top surface of the piston from increasing during the operation of the in-line six-cylinder diesel engine, thereby reducing the waste volume. It is an object of the present invention to provide an in-line six-cylinder diesel engine capable of reducing the engine speed.

[Means for solving the problem]

In order to achieve the above object, the configuration of the six-cylinder diesel engine according to the present invention is a diesel engine in which, out of six cylinders arranged in series, the crank angle of the crank pin of the central two cylinders is in phase. When stopped, the height from the center of the center piston pin to the top of the piston (hereinafter referred to as compression height)
Thus, the compression height of the other four cylinders is made higher.

Of the six cylinders, the value that sets the compression height of each of the two cylinders on both sides higher than the compression height of the central two cylinders is not constant depending on the engine scale and the like, but may be determined for each target engine. However, in general, a range of 30 to 100 μm (0.03 to 0.1 mm) can be used as a standard.

〔Example〕

Hereinafter, the present invention and its operation will be described in detail with reference to the accompanying drawings.

FIG. 1 shows # 1, # 2, # 3, # 4,
FIG. 1 is a sectional view of a main part of a diesel engine (hereinafter simply referred to as an engine) 1 of the present embodiment in which six cylinders numbered # 5 and 6 # are arranged in series. In the figure, the crankshaft includes a crank journal 23, a crank web 24, and a crankpin 26, and a connecting rod 28 is mounted between the piston pin 16 and the crankpin 26. As can be understood from the figure, cylinders 1 # and # 6, # 2 and # 5, # 3 and # 4 respectively form groups having the same phase, and the groups are out of phase with each other by 120 °. Are located.

FIG. 2 is a diagram for explaining the relationship between the compression height H and the clearance a. That is, FIG. 2 is a schematic diagram when the piston 6 is at the top dead center used in this embodiment, and the compression height H is represented by the distance between the axis of the piston pin 16 and the piston top 22. Therefore,
A clearance a which is a distance between the cylinder head lower surface 21 indicated by a two-dot chain line and the piston top 22 located at the top dead center;
The compression height H is such that one becomes larger and the other becomes smaller.

The engine 1 of this embodiment is an engine having a 1.2-liter class displacement per cylinder, and the compression height H of the cylinders # 1, # 2, # 5, and # 6 is the compression height H of the cylinders # 3 and # 4. It was manufactured so as to be 50 μm longer, and the dimensions of the other members given to the clearance a were all manufactured to the same specifications.

Next, the operation of the engine 1 of this embodiment will be described in comparison with a conventional engine. According to Table 1, except that the conventional compression height H is the same for all cylinders, an engine having exactly the same specifications as the engine 1 of the present embodiment (hereinafter referred to as a control engine) is shown with the engine stopped and during operation. 3 shows the result of actually measuring the change in the clearance a.

The clearance a when the engine is stopped is obtained by cranking a control engine that is stable at room temperature and measuring the value when the piston reaches the top dead center for each cylinder, that is, the value at which the clearance becomes the smallest. is there. As for the clearance a during the operation of the engine, a result was recorded after the operation was completed using a measuring means for recording a closest approach distance to the measurement point. The measurement points are equally spaced in the circumferential direction for each piston.
Measurement points were used. In addition, the above-mentioned operation is a continuous operation at an engine rated output (maximum output). The results shown in Table 1 are obtained by measuring 10 times at each measurement point and calculating the average value for each cylinder.

The measurement results in Table 1 are divided into two groups, cylinders # 3 and # 4, and other cylinders, and the results of averaging the measured values are shown in Table 2.

When Table 1 and Table 2 are compared, it can be understood that the dispersion of the measured values in each group is a difference within the range of the dispersion due to each member and assembly. The clearance a of the cylinders # 3 and 4 at the time of stoppage has substantially the same value as the other cylinders # 1, 2, 5, and 6 (difference of 14 μm on average), but the clearance a during operation is 71 μm shorter. That is, cylinder #
The result that the clearance reduction amount of 3,4 was larger than that of the other cylinders # 1,2,5,6 by 85 μm. In addition to this measurement, the same measurement was performed many times for other diesel engines. As a result, the clearance reduction amount of the cylinders # 3 and 4 was similar to that of the other diesel engines. The result was greater than the decrease.

The reason why the change in the clearance a of the cylinders # 3 and 4 becomes larger during operation as described above is considered as follows.
That is, since the cylinders # 3 and # 4 are arranged in the same phase and are adjacent to each other, the inertia force due to the explosion of one fuel acts as the inertia force in the opposite direction to the other cylinder, so that the clearance is increased. It is considered that the amount of decrease of “a” increases.

Therefore, in this embodiment, when the compression height H of the cylinders # 1, 2, 5, and 6 is made 50 μm (0.05 mm) longer than the compression height H of the cylinders # 3 and 4, the interference between the piston 6 and the cylinder head 12 is reduced. Further, the clearance a of each cylinder during operation could be made more uniform and smaller, and the combustion state of the engine 1 could be improved as compared with the conventional one.

[Effect of the invention]

Since the six-cylinder diesel engine of the present invention is configured as described above, the clearance between the lower surface of the cylinder head and the top surface of the piston during operation (clearance in a dynamic state).
By reducing as much as possible, the dead volume of the combustion chamber can be reduced, and compared with the case where the adjustment is performed based only on the clearance when the engine is stopped (the clearance in the static state) as before. Thus, the effect of greatly improving the combustion state during the operation of the engine can be obtained.

In addition, the above-described improvement is only to make the compression height of the other four cylinders higher than the compression height of the central two cylinders of the six cylinders arranged in series when the engine is stopped. Can be minimized, so that a highly reliable 6-cylinder diesel engine can be provided at a cost advantage.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a six-cylinder diesel engine of the present invention according to one embodiment, FIG. 2 is a diagram for explaining the relationship between the piston of the present embodiment shown in FIG. 1 and limitations defined in the present invention, FIG.
FIG. 1 is a diagram for explaining a problem with a conventional engine. 1 ... Diesel engine, 2 ... Cylinder block,
4 ... cylinder, 6 ... piston, 12 ... cylinder head, 16 ... piston pin, 21 ... cylinder head lower surface,
22 ... piston top, a ... clearance, H ... compression height (height from the axis of the piston pin to the piston top).

Claims (1)

(57) [Scope of request for utility model registration] In a diesel engine in which the crank angle of a crank pin of two central cylinders is the same among six cylinders arranged in series, a lower surface of a cylinder head and a top surface of a piston during operation of the six cylinders are provided. In order to make the clearance at the top dead center smaller,
A six-cylinder diesel engine in which the height from the axis of the piston pin to the top of the piston when the engine of the other four cylinders is stopped is higher than the height from the axis of the piston pin to the top of the piston when the engine of the cylinder is stopped.