JPH0236900Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the structure of the auxiliary combustion chamber in a diesel engine, and in particular, the auxiliary combustion chamber of a diesel engine made of ceramic is applied to the auxiliary combustion chamber of a diesel engine to improve thermal efficiency and durability. It is related to the structure of

Many attempts have been made to use ceramics in the sub-combustion chambers of diesel engines, such as vortex chambers.
Various ceramics, including silicon carbide and silicon nitride, have been tested for their high strength properties. Furthermore, in recent years, with the aim of improving fuel efficiency and thermal efficiency, attempts have been made to form the entire swirl chamber out of ceramic and utilize the heat insulating properties of ceramic to increase the temperature of the combustion gas inside the swirl chamber. For example, Japanese Utility Model Application Publication No. 58-79019 discloses a ceramic sub-chamber which is divided into an upper ceramic body and a lower ceramic body.

However, since ceramic is a brittle material, even though recent technological advances have made it a material with extremely high strength, it is susceptible to thermal shock or Failure due to stress can often occur.

That is, if the entire swirl chamber is made of ceramic, the internal walls forming the swirl chamber will be exposed to high temperatures in an extremely short period of time due to combustion heat generated within the swirl chamber. For this reason, Utsukai Showa 53
Publication No. 106508 proposes a structure in which only the nozzle part is made of ceramic and the nozzle part is further divided into two parts to prevent damage due to thermal stress. On the other hand, the ceramic outer wall portion of the swirl chamber is in close contact with the cylinder head or is in contact with the cylinder head via an air layer, a heat insulating material layer, etc., and the temperature of that portion is low. For this reason, an extremely large temperature difference appears in the thickness direction of the ceramic that forms the swirl chamber (auxiliary combustion chamber), and compressive stress is generated on the inner surface (inner surface of the swirl chamber), and tensile stress is generated on the outer surface. be in working condition.

Although ceramic generally has a high compressive fracture strength, it has low resistance to tensile stress, so if an excessive tensile force is applied to the outer surface of the ceramic auxiliary combustion chamber as described above, the outer surface will crack. occurs, and destruction begins, and this is a major factor in reducing its durability. Furthermore, in the case of a ceramic sub-chamber in which a ceramic body is fitted into a metal ring by press-fitting, shrink-fitting, etc., even if it is damaged, the characteristics will not deteriorate because it is fixed by the metal ring. The hemispherical upper ceramic body that protrudes from the metal ring receives tensile stress due to thermal stress and breaks, resulting in a decrease in durability.

The present invention was developed against this background, and aims to overcome the weakness of ceramics against tensile forces and provide a ceramic sub-combustion chamber that is highly resistant to breakage. This is the purpose.

In order to achieve this object, in the present invention, the auxiliary combustion chamber is made of an upper ceramic body having a substantially hemispherical head provided with a fuel injection nozzle hole and a glow plug hole, and a lower ceramic body having a nozzle part. In a diesel engine in which the sub-combustion chamber is fitted into a cylindrical metal ring and fitted into a recess provided in the cylinder head, the upper ceramic body is made of metal. In a plane in the direction in which the auxiliary combustion chamber is vertically divided, so as to include at least a part of the substantially hemispherical outer surface protruding from the ring, and to pass through at least one of the fuel injection nozzle hole and the glow plug hole. A dividing surface, a slit and/or a groove is provided.

As described above, according to the present invention, the substantially hemispherical outer surface of the upper ceramic body constituting the sub-combustion chamber fitted in the cylindrical metal ring has a direction in which the sub-combustion chamber is divided vertically, In other words, from the vertical dividing plane, slit and/or groove provided over a predetermined length, metal Protruding from the made ring,
Even if tensile stress is applied to the approximately hemispherical outer surface portion of the upper ceramic body forming the auxiliary combustion chamber,
Such tensile stress is effectively alleviated by the presence of predetermined dividing surfaces, slits and/or grooves provided on the outer surface, so that excessive tensile forces are not exerted thereon; This prevents the outer surface of the upper ceramic body from cracking, effectively avoiding its destruction, and improving its durability.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

First, FIG. 1 shows an example of a swirl chamber type sub-combustion chamber in which the entire swirl chamber is made of ceramic. There, 2 is a cylinder body of a diesel engine, and a piston 6 is installed in a cylinder bore 4 formed in this cylinder body 2.
are slidably fitted together so that they can be slid in the vertical direction in FIG.
On the other hand, above it, a cylinder head 10 is placed and attached via a gasket 8.
This cylinder head 10 is provided with a recess, and an upper ceramic body 14 having a substantially hemispherical top portion that forms the upper chamber of the vortex chamber 12 is mounted in the recess, and is further provided with a predetermined shape. A predetermined vortex chamber 12 is created in the cylinder head 10 by inserting the mouth body made of a ceramic body, in other words, the lower ceramic body 16 via the metal ring 18 for insertion and mounting it. It is starting to form.

Furthermore, through holes 24 and 26 are provided at the top of the upper ceramic body 14 for the glow plug 20 and the injection nozzle 22, respectively.
Glow plug 20 passing through cylinder head 10
and an injection nozzle 22 are adapted to be attached to the upper ceramic body 14. Then, such an injection nozzle 22
From there, a predetermined amount of fuel is injected into the swirl chamber 12, and the swirl chamber 12
The combustion vortex is led into the main combustion chamber 30 in which the piston 6 is placed through a communication hole (nozzle) 28 provided at the bottom of the lower ceramic body 16. . Incidentally, the upper ceramic body 14 forming the swirl chamber 12 had cracks as described above, and therefore did not have sufficient durability. This problem can be effectively solved by taking measures according to the present invention shown in .

First, FIG. 2 shows an embodiment of the present invention in which the entire vortex chamber is made of ceramic, similar to that shown in FIG. As shown in FIGS. 3 and 4, the upper ceramic body 14 is divided into two by a dividing line 32 that connects the glow plug through hole 24 and the injection nozzle through hole 26. As a result, the upper ceramic body 14 is divided into two halves 1.
It is divided into 4a and 14b. In this case, the dividing plane 34 is in the direction vertically dividing the swirl chamber 12;
In other words, it extends from the top of the swirl chamber 12 toward its bottom, and its cross-sectional shape is the second
It is shown in the figure.

By forming the dividing surface 34 on the upper ceramic body 14, the upper ceramic body 1
4, that is, the surface on the cylinder head 10 side, is effectively relaxed, thereby preventing the upper ceramic body 14 from breaking due to thermal stress and improving its durability. You get it.

Further, the division portion of the upper ceramic body 14 is not limited to the above-mentioned exemplified position, but is similar to the glow plug through hole 24.
As long as the stress concentration can be alleviated through at least one of the injection nozzle through-holes 26, the ceramic body may be inserted into the ceramic body at any position in the vertical direction, and even at a plurality of dividing planes. It is also possible to divide into three or more parts. Furthermore, if necessary,
Instead of completely dividing the ceramic body as in the above example, a dividing surface, in other words, a slit of a predetermined length, is formed locally in the ceramic body so as to include a part of the outer surface of the ceramic body. The presence of such slits can also effectively alleviate stress concentration as described above.

5 to 13 show the upper ceramic body 14.
Examples of various division positions are shown. That is, FIGS. 5 to 7 show the upper ceramic body 1.
4 is a plurality of dividing lines 40, 42, 44, 46, 4
An example is shown in which the image is divided into three or four parts by 8 and 50. 8 to 12 show slits 52, 54, 56, 58, 6 as partial dividing surfaces applied to the upper ceramic body 14.
An example of 0.62 is shown. Furthermore, Figure 13 shows that
Through holes 2 of such slits 52, 62, 64
4 and 26, the upper ceramic body 14 is separated.

Note that the upper ceramic body 14 has slits 52,
54, 60, 62, etc., a certain amount of gap will be created in the ceramic body, but such a gap may be filled with a heat-resistant filler or filled as necessary. It is closed by being covered from the outside with a suitable heat-resistant cover.

In addition, in the present invention, instead of the dividing plane or slit as described above, a predetermined groove is provided in the upper ceramic body 14 at least a part of its outer surface,
It is also effective to provide the glow plug in the vertical direction so as to pass through at least one of the glow plug through hole 24 and the injection nozzle through hole 26, an example of which is shown in FIGS. 14 and 15. There is. There, the upper ceramic body 14 is
It has a groove 66 extending all the way around its outer surface. That is, the groove portion 66
It is provided at the same location as the dividing line 32 shown in the figure. By providing the groove portion 66 having a predetermined depth in the thickness direction of the ceramic body on the outer surface of the upper ceramic body 14, stress concentration on the outer surface of the ceramic body 14 can be effectively alleviated. This suppresses the occurrence of cracks and even their destruction,
Therefore, its durability can be increased.

The depth of the groove 66 is appropriately determined depending on the thickness of the ceramic body 14 so as to achieve the desired stress relaxation.
Further, the bottom of the groove 66 is desirably formed in a circular shape as shown in FIG. 15 or widened toward the bottom in order to prevent stress concentration.

Furthermore, such a groove 66 may be formed not only over the entire circumference of the ceramic body 14 as illustrated in FIG. There is no problem with this, and the arrangement pattern is the fifth one.
Any of the forms illustrated below can be adopted.

Further, in the present invention, in addition to the above-mentioned dividing planes, slits and/or grooves provided in the vertical direction of the upper ceramic body 14, horizontal dividing planes, slits and/or grooves are provided in the upper ceramic body 14.
It is also possible to provide it in 4. This lateral dividing plane, slit or groove is located within a plane in the direction of horizontally dividing the sub-combustion chamber such as the swirl chamber, and is formed so as to include at least a portion of the outer surface of the ceramic body. That will happen. FIGS. 16 and 17 show an example, in which the upper ceramic body 14 is separated by a vertical dividing line 68.
By joining the horizontal dividing line 70, the hemispherical portion at the top is divided into halves. In addition, in another example shown in FIG. 18, due to a vertical dividing line 72 different from the dividing line 68, the dividing portion of the spherical portion at the top of the ceramic body 14 is approximately half that of the previous example. It is becoming. In any case, such horizontally provided dividing surfaces, slits, or grooves, together with vertically dividing surfaces, slits, or grooves, can effectively contribute to alleviating stress concentration on the outer surface of the ceramic body. .

As described above in detail based on several embodiments, by dividing the upper ceramic body forming the auxiliary combustion chamber at least in the vertical direction, or by forming vertical slits or grooves therein, such a ceramic body can be formed. Thermal stresses acting on the body are effectively relieved, thereby increasing the resistance of the ceramic body to fracture,
As a result, the durability of the ceramic auxiliary combustion chamber was significantly improved.

The ceramic bodies used in the present invention include silicon nitride, silicon carbide, zirconia, zircon,
Mullite, cordierite, lithium aluminum silicate, aluminum titanate, magnesium aluminum silicate,
It may be made of any ceramic material such as SIALON, crystallized glass, or a composite thereof, and it is also possible to use ceramic materials other than these. Also,
The ceramic body located in the upper part of the sub-combustion chamber is preferably formed of a ceramic material with particularly good heat insulation properties, such as crystallized glass, zirconia, high-strength electrically insulating porcelain, etc. The body is preferably made of a material such as silicon nitride that has excellent heat resistance and thermal shock resistance.

In addition, in the above explanation, the ceramic body that constitutes the swirl chamber, which is one of the auxiliary combustion chambers, has been mainly described, but other types of auxiliary combustion chambers,
For example, the same applies to pre-combustion chamber type devices, etc., and it goes without saying that the present invention can be suitably applied even when a ceramic body is used for such pre-combustion chamber type devices. By the way.

Further, even if the upper ceramic body is formed of two or more ceramic bodies, for example, a top ceramic body and a body ceramic body, the present invention can be effectively applied, and the present invention can also be applied. For inserting the ceramic body provided with dividing surfaces, slits and/or grooves into the cylinder head, known outer rings and positioning means are used as appropriate. Providing a heat insulating layer, a heat insulating material layer, etc. between the head and the head is a means that can be adopted as appropriate.

In addition, various changes, improvements, modifications, etc. may be made to the present invention without departing from the spirit of the present invention, and the present invention includes embodiments made with such changes. It goes without saying that these are also included within this scope.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical cross-sectional view showing a sub-combustion chamber portion of the cylinder head. FIG. 2 is a longitudinal cross-sectional view of an auxiliary combustion chamber according to an example of the present invention, FIG. 3 is a plan view thereof, FIG. 4 is an exploded perspective view of its upper ceramic body, and FIGS. 5 to 13 are respectively FIG. 14 is a plan view showing an example of the arrangement of dividing surfaces, slits, or grooves in the upper ceramic body, and FIG. 14 is a longitudinal sectional view of the upper ceramic body provided with grooves, showing another embodiment of the present invention; FIG. 15 is a sectional view taken along the line A-A in FIG. 14, and FIG. 16 is a side view showing still another embodiment of the present invention in which a vertical dividing surface and a horizontal dividing surface are provided. FIG. 17 is a perspective view thereof, and FIG. 18 is a perspective view of another embodiment of the present invention showing an example of an upper ceramic body provided with two longitudinal dividing surfaces and one horizontal dividing surface. It is. 10: cylinder head, 12: swirl chamber, 14:
Upper ceramic body, 16: Lower ceramic body, 2
4, 26: Through hole, 28: Communication hole (spout), 3
4: Division plane, 32, 40, 42, 44, 46, 4
8, 50: Parting line, 52, 54, 56, 58, 6
0, 62, 64: slit, 66: groove.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The auxiliary combustion chamber is composed of an upper ceramic body having a substantially hemispherical head provided with a fuel injection nozzle hole and a glow plug hole, and a lower ceramic body having a nozzle part. In addition, in a diesel engine in which the auxiliary combustion chamber is fitted into a cylindrical metal ring and is fitted into a recess provided in the cylinder head, the upper ceramic body has a substantially hemispherical part that protrudes from the metal ring. a dividing surface or slit that includes at least a part of the outer surface of the auxiliary combustion chamber and is located in a plane in a direction in which the auxiliary combustion chamber is vertically divided so as to pass through at least one of the fuel injection nozzle hole and the glow plug hole; A structure of an auxiliary combustion chamber in a diesel engine, characterized in that it is provided with a groove and/or a groove. (2) The structure of the auxiliary combustion chamber according to claim 1, wherein the dividing surface, slit, and/or groove are provided all around the outer surface of the ceramic body. (3) Utility model registration claim 1, wherein the upper ceramic body includes a dividing surface, a slit, and/or a groove in a direction that horizontally divides the auxiliary combustion chamber so as to include at least a part of its outer surface. Or the structure of the auxiliary combustion chamber according to any of item 2. (4) The structure of the auxiliary combustion chamber according to claim 1 or 3, wherein the groove is formed in a circular shape at its bottom or widens toward the bottom. (5) The structure of the sub-combustion chamber according to claim 1, wherein the sub-combustion chamber is a swirl chamber. (6) The structure of the sub-combustion chamber according to claim 1, wherein the sub-combustion chamber is a pre-combustion chamber.