JPH0549809B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diesel engine, and particularly to a diesel engine in which the temperature inside a combustion chamber partitioned with ceramic can be adjusted to improve the filling efficiency of intake air. Regarding.

[Conventional technology]

In general, adiabatic engines are known in which the inner wall surface of the piston's combustion chamber is coated with a heat-resistant material, or in which a part of the combustion chamber is made of a heat-resistant material. It is used.

Such adiabatic engines try to suppress heat dissipation and improve thermal efficiency by using heat-resistant materials, but the air sucked into the combustion chamber is Since the air is expanded by receiving heat, the mass of the air in the cinder is reduced, the filling efficiency of the intake air is reduced, and combustion becomes unstable.

For this reason, the present applicant has previously proposed an adiabatic diesel engine (Japanese Utility Model Application Publication No. 163634/1983).

As shown in FIG. 7, this proposal constructs an adiabatic diesel engine by providing an injection device b for injecting fuel and water in a combustion chamber a partitioned with ceramic.

[Problem that the invention seeks to solve]

The above proposal is an attempt to improve the air filling efficiency by lowering the temperature of the wall surface that partitions the combustion chamber by using water spray.

However, using an injection pump to inject water and fuel from a nozzle as proposed in this proposal is not only expensive, but also results in excessive cooling of the wall of the combustion chamber facing the nozzle, and There was a problem that the moisture required for the process remained.

[Means for solving problems]

In order to solve the above problems, the present invention connects an air passage to a combustion chamber partitioned by ceramic to supply high-pressure air along the circumferential direction of the combustion chamber, and cools the air passage. A spray generator is provided to supply the spray, and an on-off valve is provided in the air passage at a position closer to the combustion chamber than the spray generator, and is opened after the latter half of the exhaust stroke and closed at the same time as the exhaust valve at the beginning of the intake stroke. It was established.

[Effect]

The on-off valve is opened while the engine is in the second half of its exhaust stroke and ends in the beginning of its intake stroke. Therefore, at this time, cooling air containing a mixture of cooling spray and high-pressure air is supplied from the air passage into the combustion chamber. The cooling air swirls around the combustion chamber in the circumferential direction, uniformly absorbing heat from the inner wall surface that partitions the combustion chamber, vaporizes and expands, and is discharged from the combustion chamber to the outside of the combustion chamber by high-pressure air. . This prevents an excessive temperature rise in the combustion chamber atmosphere without impairing the heat insulation performance of the combustion chamber, and improves the intake air filling efficiency.

〔Example〕

Hereinafter, a preferred embodiment of the diesel engine of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, 1 is a cylinder body, and 2 is a cylinder head. As shown in the figure, a plurality of cylinders 3 are arranged in a cylindrical shape in a cylinder body 1, and a cylindrical cylinder liner 4 is integrally fitted into each cylinder 3. A cylindrical piston 5 is accommodated in the cylinder liner 4 so as to be able to reciprocate along an inner wall 4a of the liner 4 (hereinafter referred to as the "liner inner wall"). A plurality of piston rings 6 are fitted around the circumference of the piston 5, and these piston rings 6 form a predetermined clearance between the liner inner wall 4a and the piston 5.
Further, a cavity 8 is formed in the piston top 7 of the piston 5, which is recessed in the axial direction from the top 7 and into which fuel is supplied. In this embodiment, the cavity 8 has a toroidal shape with a raised center at the bottom.

The cylinder head 2, cylinder liner 4 and piston 5 are made of ceramic, and the cylinder head 2, liner inner wall 4a, piston top 7,
A highly insulated combustion chamber 9 is formed in the cavity 8 .

Now, the feature of the diesel engine of the present invention is that it lowers the combustion chamber atmospheric temperature and increases the charging efficiency without impairing the heat insulation performance of the combustion chamber.

Therefore, it is configured as follows.

As shown in FIGS. 1 and 2, an intake port 10 and an exhaust port 11 are opened in parallel on the surface of the cylinder head 2 that seats on the cylinder body 1.
A supply port 21 is opened between the intake and exhaust ports 10 and 11 and located on the outer peripheral side of the cylinder liner 4. In this embodiment, the opening diameters are as follows: intake port>exhaust port>supply port.

On the other hand, the cylinder head 2 has an intake/exhaust passage 1
2 and 13 are formed, respectively, and these suction/exhaust passages 12, 13 are connected to the suction/exhaust ports 10, 11, respectively. Furthermore, as shown in FIG. 6, an air passage 14 for high-pressure air is formed in the cylinder head 2, with one end connected to the compressor of the turbocharger 40 and the other end connected to the supply port 21. ing. Further, as shown in FIGS. 1 and 2, the passages 12, 13, and 14 of the cylinder liner 4 are connected. Suction/exhaust ports 10, 11 and supply port 2
The cavity 8 side of 1 is expanded in diameter into a cylindrical shape, and valve seats 15, 1 are provided in the expanded diameter portion.
6 and 17 are integrally fitted.

An intake valve 18, an exhaust valve 19, and an on-off valve 20 are housed in the cylinder head 2 so as to be able to reciprocate.
, the exhaust valve 19 is connected to the valve seat 16 of the exhaust port 11.
, the on-off valve 20 is connected to the valve seat 17 of the supply port 21.
They are adapted to be engaged and disengaged respectively.

The air passage 14 is provided with a spray generator 23 that supplies cooling spray into the air passage 14 .

This spray generator 23 divides a casing 24 into upper and lower parts by a piezoelectric element member 25, and provides a supply means 26 above the piezoelectric element member 25 for supplying a cooling medium such as water. Generating high frequency waves in the element member 25,
The controller 27 is provided with a controller 27 that vibrates the piezoelectric element member 25 in accordance with the frequency to generate cooling spray in the upper chamber 28 of the casing 24. That is, in the upper chamber 28 of the casing 24,
The air passage 14 is connected to the controller 27.
Cooling spray is generated by variably controlling the frequency of the piezoelectric element member 25 according to the load and rotation speed.

Next, the intake/exhaust valves 18, 19 and the on-off valve 2
The cyclic closing timing of 0 will be explained based on FIG.

In the figure, the broken line shows the opening/closing timing and lift of the conventional intake valve, the broken line shows the opening/closing timing and lift of the conventional exhaust valve, and the solid line shows the intake valve 18 of this embodiment.
The solid line shows the opening/closing timing and lift of the exhaust valve 18 of this embodiment, and the two-dot chain line shows the opening/closing timing and lift of the on-off valve 20 according to the present invention.

As shown in the figure, the intake valve 18 of this embodiment is set to open at a position closer to TDC (top dead center position) than the conventional one, and the exhaust valve 19 of this embodiment is set to open at the BDC position (similar to the conventional one). (bottom dead center position) opened in front.
It is designed to close after passing the TDC position. Note that a shorter overlap period is set between the opening timing of the intake valve 18 and the closing timing of the exhaust valve 19 than in the past. And the on-off valve 20 is
It is set to open after the latter half of the exhaust stroke and close at the same time as the exhaust valve 19.

The operation of the embodiment of the diesel engine of the present invention will be explained below based on the accompanying drawings.

Since the combustion chamber 9 is partitioned by ceramic, its heat insulation properties are improved. Therefore, even if the atmospheric temperature is extremely low, the temperature of the combustion chamber 9 is quickly raised.

As shown in FIG. 3, the on-off valve 20 is opened from the latter half of the exhaust stroke to the beginning of the intake stroke. Therefore, the cooling air, which is a mixture of the cooling spray generated by the supply spray generator 23 and high-pressure air, is supplied into the combustion chamber 9 from the latter half of the exhaust stroke to the early stage of the intake stroke. This cooling air is
It flows along the liner inner wall 4a in the circumferential direction of the combustion chamber 9, and while swirling around the combustion chamber 9, it absorbs heat from the surfaces of the liner inner wall 4a and the cavity 8, vaporizes and expands, and is discharged from the exhaust passage 13 to the outside by high-pressure air. It is discharged.

That is, the cooling air and exhaust gas (hot air) after vaporization can be discharged from the combustion chamber 9 to the outside through the exhaust passage 13 without leaving them in the combustion chamber 9, and the combustion can be carried out without reducing the overall insulation properties. Room 9
And only the surface of the liner inner wall 4a can be cooled. Therefore, the charging efficiency of intake air can be maintained at a constant level, and stable combustion can be maintained.

Next, another embodiment will be described based on FIGS. 4 and 5.

4 and 5, 1a is a cylinder body, 2a is a cylinder head, 4c is a first cylinder liner, 4d is a second cylinder liner, 5a is a piston, 9 is a combustion chamber, and 41 is a fuel injection nozzle. . The fuel injection nozzles 41 are arranged with their injection holes facing the combustion chamber 9, and are configured to inject fuel in directions that divide the circumferential direction of the combustion chamber 9 into approximately equal parts.

In the embodiment, the second cylinder liner 4d
The piston 5a is vertically divided into an upper cylinder liner 4e and a lower cylinder liner 4f.
It is also vertically divided into an upper piston 5b and a lower piston 5c. Upper cylinder liner 4
The top of e is closed. The upper cylinder liner 4e, lower cylinder liner 4f, and upper piston 5b are integrally molded from ceramic. Further, the lower piston 5c is molded from a metal material such as aluminum, and is integrally formed with the upper piston 5b.

A first cylinder liner 4c is integrally fitted into the cylinder 3, and a flange portion that is seated and fitted onto the cylinder body 1a is integrally formed at the upper end of the first cylinder liner 4c. has been done. Further, the first cylinder liner 4c has a portion facing the upper cylinder liner 4e that is expanded in diameter in the radial direction relative to other portions. And the enlarged diameter part 4
2, a ring-shaped gasket 43 is interposed at a predetermined interval in the axial direction of the first cylinder liner 4c.

That is, the gasket 43 forms an air-insulating space between the first cylinder liner 4c and the upper cylinder liner 4e. Further, a ring-shaped gasket 44 is interposed between the closed portion 4g of the upper cylinder liner 4e and the lower surface of the cylinder head 2a to form a heat insulating space.

Now, in this embodiment, the supply port 21a opened in the upper cylinder liner 4e is supplied to the combustion chamber 9 from the helical intake passage 12 formed in the cylinder head 2a, as shown in FIG. It is opened so as to face the flow of intake air, that is, the swirl S of combustion air, and to supply air thereto. The opening end of the air passage 14 on the combustion chamber 9 side is connected to the supply port 21a.

In other words, in this embodiment, a negative swirl is generated in advance in the combustion chamber 9 using cooling air to moderately weaken the swirl S of the combustion air, and mutual interference between the fuel sprays due to the swirl S is prevented. The aim is to improve combustibility and reduce smoke emissions.

In the explanation of this embodiment, the turbocharger 40 was used as the introduction source of high-pressure air, but it goes without saying that any device that produces high-pressure air for the combustion chamber 9 may be used. .

〔Effect of the invention〕

As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) The atmospheric temperature in the combustion chamber can be lowered to a temperature at which a constant charging efficiency can be obtained without impairing the insulation properties of the combustion chamber, and stable combustion performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a preferred embodiment of the diesel engine according to the present invention, FIG. 2 is a top view of FIG. 1, and FIG. 4 and 5 are schematic views showing other embodiments, FIG. 6 is an overall view of a diesel engine according to the present invention, and FIG. 7 is a schematic view showing a conventional adiabatic diesel engine. In the figure, 1 is a cylinder body, 2 is a cylinder head, 9 is a combustion chamber, 14 is an air passage, 20 is an on-off valve, and 23 is a spray generator.

Claims (1)

[Claims] 1. An air passage is connected to a combustion chamber defined by ceramic to supply high-pressure air along the circumferential direction of the combustion chamber, and cooling spray is supplied to the air passage. A spray generator is provided in order to achieve this, and an on-off valve is provided in the air passage at a position closer to the combustion chamber than the spray generator, and is opened after the latter half of the exhaust stroke and closed at the same time as the exhaust valve at the beginning of the intake stroke. A diesel engine characterized by: 2. The diesel engine according to claim 1, wherein the open end of the air passage facing the combustion chamber faces the swirl of the combustion chamber.