JPS6332925Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a new diesel engine, in particular, the top of the piston is recessed to form a combustion chamber, and the wall surface of the combustion chamber is improved to increase combustion efficiency. This relates to a diesel engine.

[Conventional technology]

In diesel engines, the combustion chamber system has been switched from the conventional auxiliary combustion chamber system to a direct injection system (so-called direct injection system) in order to improve fuel efficiency from the perspective of energy conservation.

However, in direct injection combustion chambers, the surface area of the piston combustion chamber wall is generally large enough to easily cool the combustion gas, and many sprayed fuels have the above-mentioned problems due to the inertia of the injection and the strong swirl flow inside the combustion chamber. Since the piston is unevenly distributed near the wall of the combustion chamber, the atomized fuel is cooled by the wall of the piston combustion chamber and its temperature decreases, making it difficult to evaporate, and furthermore, the atomized fuel cannot be quickly and sufficiently mixed with air. Therefore, it is difficult to achieve complete combustion in a short period of time, making it impossible to improve fuel efficiency, and also producing black smoke and harmful
It has the disadvantage of easily generating CO, HC, etc., and this has been the cause of hindering the introduction of direct injection in small, high-speed diesel engines.

[Problem that the invention attempts to solve]

Conventionally, a method of coating the piston combustion chamber wall with ceramics was used to insulate the piston combustion chamber wall, but this method does not provide a heat insulation effect if the coating layer is thin, and may peel if it is thick. Therefore, it is difficult to provide insulation using ceramic coating. Another disadvantage was that it was expensive. On the other hand, attempts have been made to create large irregularities inside the combustion chamber to promote the mixing of fuel and air, but these irregularities act as resistance to the swirl flow, making it impossible to maintain a stable swirl flow. There were flaws.

The present invention was created to effectively solve the above problems.

The present invention makes it possible to maintain the wall of the combustion chamber formed at the top of the piston at a high temperature, thereby reducing unburned substances and promoting the mixing of fuel and air, thereby providing a diesel engine that can achieve complete combustion in a short period of time. The purpose is to

[Means and actions for solving problems]

The present invention forms a concave combustion chamber at the top of the piston, and covers the top surface of the piston containing the combustion chamber with a ventilated porous heat-resistant wall with a predetermined gap between the ventilated porous heat-resistant wall and the above. The gap with the top surface is filled with heat-resistant granules such as ceramic, alumina, or steel, and the piston and combustion chamber are insulated by the heat-resistant granules, and the heat-resistant granules and ventilation holes are A turbulent flow is formed by the voids and irregularities formed in the heat-resistant wall, and the turbulent flow promotes mixing of fuel and air.

〔Example〕

The present invention will be explained below with reference to an embodiment shown in FIGS. 1 and 2.

The cylinder 1 is composed of a cylinder liner 2, a cylinder head 3, and a gasket 4 that seals the gap between them. The cylinder head 3 is provided with a fuel injection nozzle 5 and intake and exhaust ports that can be opened and closed by a valve mechanism (not shown).

The piston 6 is the cylinder liner 2 of each cylinder 1.
A combustion chamber 9 is provided in the center of the top of the piston body 8 and is recessed in the shape of a cup. The surface part is covered with a predetermined gap and has small holes 1 of similar shape.
A heat-resistant porous air-permeable wall 10 made of a wire mesh or the like having a large number of 0a is coated, and a heat-resistant material such as ceramic, alumina, steel, etc. The heat-resistant granules 11 having a diameter of 1 to 3 mm are filled with heat-resistant particles 11 made of (or a refractory material) or a mixture thereof with a catalyst for promoting combustion. In order to fix the heat-resistant granules 11 to the wall of the combustion chamber 9 using the air-permeable porous heat-resistant wall 10, the outer dimensions of the combustion chamber 8 are made smaller by about 3 mm.

Further, a fixing groove 12 is fixedly provided on the circumferential surface of the piston 6, and an inward flange 10b provided at the opening edge of the breathable porous heat-resistant wall 10 is pressed into this fixing groove 12 by a press. . In addition, heat-resistant granules 1
1 is solidified with a low-flux material such as wax and is preformed into a size and shape that can be inserted between the combustion chamber 9 wall and the air permeable porous heat-resistant wall 10. Therefore, appropriate spaces are formed between the heat-resistant granules 11 and unevenness is formed between the granules, and the heat-resistant granules 11 are held at the top of the piston 6 by the air-permeable porous heat-resistant wall 10. The piston combustion chamber wall 13, which has numerous voids and relatively large irregularities on its surface, is substantially formed into a combustion chamber 14.
will be divided into sections.

In the above configuration, the piston combustion chamber wall 13 is made up of the layered heat-resistant granules 11 covering the top surface of the piston body 8 and the breathable porous heat-resistant wall 10, and the piston combustion chamber wall 13 includes the combustion chamber 14.
As a result, a strong swirl flow is generated by the rise of the piston 6, and a small excess flow of air is generated on the combustion chamber wall 13 to the extent that it does not create resistance to the swirl flow. A large amount of turbulence is generated near the wall surface, and this turbulent flow stirs the atmosphere within the combustion chamber 14. Therefore, high-pressure fuel is injected in the form of a mist from the fuel injection nozzle 5, and even if the fuel is unevenly distributed near the wall surface due to its inertia, the atomized fuel and air are mixed very quickly. Moreover, the air becomes high-pressure and high-temperature due to the rise of the piston 6, and the piston combustion chamber wall 13 is maintained at a higher temperature than the piston body 8, so the combustion chamber 14 and the piston body 8 are insulated, and combustion heat is transferred to the piston 6. At the same time, the atomized fuel quickly evaporates and gasifies due to the stirring action of the swirl flow and the eddy flow on the wall surface. Therefore, complete combustion occurs in a short period of time, no black smoke, harmful CO, HC, etc. are generated, and the volume is increased, resulting in increased output and improved fuel efficiency. When the heat-resistant granules 11 contain a catalyst, the combustion reaction at low temperatures is facilitated, and the generation of the black smoke and the like in a low load range is reduced.

Furthermore, although the wall area of the piston combustion chamber wall 13 has increased, its function as an insulating wall makes it difficult for the sprayed fuel (or fuel gas) and air near the wall surface to be cooled down by the piston body 8, making it difficult to start the engine in cold weather. It's easy.

Furthermore, the piston combustion chamber wall 13 is made of heat-resistant granules 1
1 is held by the breathable porous heat-resistant wall 10, it has flexibility, and unlike ceramic coatings, cracks do not occur due to thermal shock or thermal expansion difference. It can absorb the shock when the pressure suddenly rises, does not come off the piston body 8, and transmits the descending force while buffering the shock and exhibits a gas damper function, thereby reducing combustion noise.

As described above, the present invention is a simple improvement of the piston combustion chamber wall, but it can reliably promote combustion near the piston combustion chamber wall, which was the biggest drawback of direct injection combustion chambers, and is suitable for use in small high-speed diesel engines. This opens the door to direct injection.

[Effect of idea]

In summary, the present invention provides the following excellent effects.

(1) Cover the top surface of the piston, including the combustion chamber, with a ventilated porous heat-resistant wall at a predetermined gap, and cover the ventilated porous heat-resistant wall with a heat-resistant material such as ceramic in the gap between the piston top surface and the piston top surface. Since the granular material is filled, the voids formed by the heat-resistant granular material and the breathable porous heat-resistant wall and the relatively large irregularities form countless vortices, so that the fuel and air are quickly mixed, and the air is quickly mixed. As combustion is achieved and the degree of isovolume increases, the power increases,
And fuel efficiency improves.

(2) Unburned gas and air near the wall surface become difficult to cool, so soot, CO, and HC are generated during combustion.
It is difficult to generate harmful substances such as

(3) Air-permeable porous heat-resistant walls and heat-resistant granules have flexibility, so they do not suffer from cracking due to thermal buffering and the difference in thermal expansion between the metal and the wall, as with ceramic coated walls, skin-shaped walls, and semi-integrated walls. Highly safe.

(4) Low-noise combustion can be achieved because the breathable porous heat-resistant walls and heat-resistant granules function as a gas damper that can absorb shock waves caused by explosive combustion.

(5) The breathable porous heat-resistant wall does not provide resistance to swirl, so it does not reduce the swirl flow.

(6) Since the heat-resistant granules can contain a catalyst, the combustion reaction can be easily carried out even in the low temperature range, and the occurrence of smoke etc. in the low load range can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, and FIG. 2 is a plan view showing a piston combustion chamber portion in FIG. 1. In the figure, 1 is the cylinder, 2 is the cylinder liner, and 3
is the cylinder head, 4 is the gasket, 5 is the fuel injection nozzle, 6 is the piston, 7 is the piston ring,
8 is a piston main body, 9 is a combustion chamber, 10 is a breathable porous heat-resistant wall, 10a is a small hole, 10b is a flange, 11 is a heat-resistant granule, 12 is a fixed groove, 13 is a piston combustion chamber wall (insulation wall) It is.

Claims (1)

[Scope of utility model registration request] A recessed combustion chamber is formed at the top of the piston, and the top surface of the piston containing the combustion chamber is covered with a ventilated porous heat-resistant wall with a predetermined gap between the ventilated porous heat-resistant wall and the top surface. A diesel engine characterized by filling the gaps with heat-resistant granules such as ceramic, alumina, or steel.