JPS60113021A - Nozzle part for auxiliary chamber of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent rupture of a nozzle part, by a method wherein a nozzle part for the auxiliary chamber of an internal-combustion engine is made of a ceramic sintering material, and a ceramic porous material is used in a surface part where a high thermal strain is yielded due to cooling of a cylinder block. CONSTITUTION:A nozzle part for an auxiliary chamber is formed with a body 1 and a surface part 2 integrally formed on the surface the body, and a nozzle hole 3 is formed in the base thereof. The nozzle part is formed such that sintering powder consisting of mainly silicon nitrogen is injection-molded togetherwith a binder, and the molding is sintered under a nitrogen gas atmosphere to form the body 1. Thereafter, alcohole is added to mixture of alumina fiber and alumina to prepare slurry. Slurry is applied on a surface part, centring aroung a boundary part between the side and the bottom of the body 1, and after it is dried, the resultant work is sintered under a nitrogen gas atmosphere to form a surface part 2 formed by a ceramic porous material. When, with the nozzle mounted to a diesel engine, full load operation is effected, a thermal stress exerted on the nozzle part is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a mouthpiece part for a pre-chamber of an internal combustion engine such as a diesel engine.

The combustion chambers of internal combustion engines such as Kallin engines and diesel engines, especially the pre-chamber mouthpieces interposed between the pre-chamber and the main combustion chamber, require strength and heat resistance, so heat-resistant alloys are usually used. Met.

Furthermore, recently, the use of ceramic parts in place of heat-resistant alloys has been considered. The use of this ceramic component satisfies the heat resistance and durability required for a pre-chamber mouthpiece component of an internal combustion engine, thereby improving the reliability of the internal combustion engine.

[Prior Art] Conventionally, a ceramic sub-chamber mouthpiece part is made of a dense ceramic sintered body of silicon nitride, silicon carbide, alumina, or the like. When a pre-chamber mouthpiece made of this dense ceramic sintered body is used fixed between the main combustion chamber and the sub-combustion chamber of an internal combustion engine, it is known that the mouthpiece often cracks and breaks. . This is the part where the ceramic mouthpiece comes into contact with a metal part such as a cylinder block, and a portion of the ceramic mouthpiece is cooled by the metal cooling. It is thought that this causes thermal stress, which causes a relatively small crack to grow on the surface of the ceramic die part, leading to fatal failure.

[Object of the Invention] An object of the present invention is to provide a ceramic mouthpiece part for a pre-chamber of an internal combustion engine that is difficult to break. Furthermore,
The purpose of the present invention is to provide a cap part for a subchamber that is easy to cause injury.

[Detailed Description of the Invention] The auxiliary chamber mouthpiece part for an internal combustion engine of the present invention is fixed between a main combustion chamber and an auxiliary combustion chamber of a metal cylinder block, and communicates between the main combustion chamber and the auxiliary combustion chamber. A sub-chamber mouthpiece made of ceramics having a nozzle hole at the bottom, the entire body being formed of a dense ceramic sintered body, and at least a part of the bottom surface and the side surfaces centering on the boundary between the bottom surface and the side surfaces. The surface portion including a part of is formed of a porous ceramic body.

In the subchamber mouthpiece component of the present invention, the surface portion at the boundary between the bottom and side surfaces is formed of a porous ceramic body. The heat insulating properties of this ceramic porous body prevent large thermal distortions of the cap parts that occur due to heat dissipation to the metal parts due to contact with metal parts, and prevent the occurrence of large thermal distortions of the cap parts, which are made of dense ceramics that make up the majority of the cap parts. This prevents the propagation of cracks into the structure and the growth of cracks. For this reason, by using the sub-chamber mouthpiece component of the present invention, the occurrence of cracks due to thermal distortion can be largely prevented.

[Detailed description of the structure of the invention] The pre-chamber mouthpiece part of the internal combustion engine of the present invention is fixed between the main combustion chamber and the sub-combustion chamber of a metal cylinder block in the same way as conventional pre-chamber mouthpiece parts. . Therefore, the upper end surface of this mouthpiece component forms a partition that partitions the auxiliary combustion chamber, and the lower end surface of this auxiliary chamber mouthpiece component constitutes a side wall that divides the main combustion chamber. The auxiliary chamber mouthpiece part is usually in the shape of a container having a nozzle hole at the bottom that communicates the main combustion chamber and the auxiliary combustion chamber. The shape of the sub-chamber cap part of the present invention may be the same as that of the conventional sub-chamber cap part, or may have various shapes that will be developed in the future.

Almost the whole of the sub-chamber mouthpiece part of the present invention is made of a dense ceramic sintered body, similar to conventional ceramic mouthpiece parts. Here, dense means that the porosity is 5% or less. The material of the sintered body may be any material as long as it has the heat resistance and strength required for the die part, and as in the past, alumina, silicon nitride, silicon carbide, etc. can be used.

The ceramic porous body that characterizes the sub-chamber mouthpiece component of the present invention is formed on a surface portion centered on the boundary between the bottom and side surfaces of the mouthpiece component and including at least a portion of the bottom surface and a portion of the side surfaces. . Note that this part is the part where the largest thermal strain occurs due to heating by the high temperature jet gas passing through the nozzle hole and cooling by the cylinder block. The ceramic porous body is provided in the portion where the largest thermal strain occurs. The porous ceramic body can be provided on a surface portion that forms the entire surface that is in contact with the metal surface of the cylinder block. Further, it is preferable to increase the thickness of the ceramic porous body in areas where thermal strain is large.

The porosity of the porous ceramic body is preferably 10 to 50%. The ceramic forming the porous ceramic body may be made of the same material as the dense ceramic sintered body or may be made of a different material. Further, the ceramic porous body may contain reinforcing ceramic fibers or whiskers.

In the sub-chamber mouthpiece part of the present invention, first, almost the entire mouthpiece part is formed from a dense ceramic sintered body, and then the portion that will become the porous ceramic body is made of ceramic powder or reinforcing fibers are added to the ceramic powder. It can be manufactured by forming a mixed slurry or the like and sintering it again.

[Effects of the Invention] In the pre-chamber mouthpiece part for an internal combustion engine according to the present invention, the surface portion where large thermal distortion occurs due to cooling of the cylinder block is made of a porous ceramic material. Therefore, due to the low thermal conductivity (excellent heat insulating properties) of this porous ceramic body, large thermal distortions are prevented from occurring. Furthermore, cracks due to thermal strain occur in the porous ceramic body, and these cracks do not propagate to the dense ceramic sintered body. For this reason, the dense ceramic sintered body that constitutes almost the entire part of the cap part is free from cracks and growth, and a durable cap part can be obtained.

[Example] In addition, since the base part of the present invention can be used by directly assembling it into a cylinder block, assembly becomes easy. Further, since the cap part of the present invention has excellent heat insulation properties, the ignitability of the engine is improved.

FIG. 1 is a cross-sectional view of a sub-chamber mouthpiece part for an internal combustion engine according to a first embodiment of the present invention, and FIG. 2 is a back view thereof. This mouthpiece component is composed of a main body 1 made of a dense silicon nitride sintered body and a surface portion 2 made of an alumina porous body integrally formed on the surface of the main body 1. This base part is cup-shaped and has a nozzle hole 3 at its bottom. This die part is made by first injection molding a sintered body powder whose main component is silicon nitride together with a binder, as in the past, and after degreasing the resulting molded body, it is sintered at 1750°C for 4 hours in a nitrogen gas atmosphere. Then, a main body l was formed. The porosity of this main body 1 was 2%. Next, alumina fiber 3 with an average diameter of 3 μm and a length of 100 μm
A slurry was formed by adding alcohol to a mixture of 0% by weight and 70% by weight of alumina having a particle size of about 0.5μ. Using this slurry, as shown in Figure 1, apply the slurry to the surface area of the sintered body, centering on the boundary between the side and bottom surfaces, and after drying, sinter at 1000℃ for 2 hours in a nitrogen gas atmosphere. Then, a surface portion 2 made of a porous ceramic body was formed. The porosity of this ceramic porous body is 25%
Met.

Next, in order to observe the temperature distortion of this cap part, thermistors were embedded at points A and B, which are not shown in the cross section of FIG. After that, as shown in the cross section of the main part in Fig. 3, this cap part was
air! It was assembled between the cylinder block 4 and cylinder head 5 of a 2400 cc diesel engine. Then, drive the engine at 4.40 Orpm and full load,
The temperatures at point A and point B at this time were measured to test the temperature and durability of the cap parts. In addition, a thermistor was similarly embedded at points A and B shown in Fig. 1 using a mouthpiece part made entirely of uniform silicon nitride sintered body as a comparison mouthpiece part, and the part was assembled into the same engine. Temperature was measured.

The measured temperature of the cap parts in this example is 650°C at point B.
, A point was 850°C. On the other hand, the measured temperature at point B of the conventional cap part was 400°C, and at point A was 800°C. The temperature measured at point B of the base component of this embodiment is 660° C., and the temperature measured at point B of the conventional base component is 400° C., so the temperature at point B of the base component of this embodiment is extremely high. In addition, the temperature of the wall near the sub-combustion chamber is 850℃, which is 850℃ compared to the conventional nozzle part.
50℃ higher than 0℃. From these results, it was confirmed that the temperature difference between points A and B in the cap part of the first example was about half as small as that in the conventional cap part. From this result, it can be seen that the thermal stress acting on the cap parts is reduced. Furthermore, since the temperature of the mouthpiece is maintained higher than that of conventional mouthpiece parts, the inner surface of the combustion chamber is maintained at a high temperature. This is expected to improve ignition performance.

Example 2 The same silicon nitride sintered body as used in Example 1 was mainly used. As a ceramic porous body, the average particle size is 5.
A silicon nitride powder of μ was slip-cast, molded, and then fired. This slip cast is formed on the surface centering on the boundary between the bottom and side surfaces of the main body as in the first embodiment, and is sintered at 1350°C for 2 hours in a nitrogen gas atmosphere to form a ceramic porous body. was formed.

Similarly to Example 1, thermistors were embedded in the mouthpiece parts of Example 2 at points A and B in FIG. 1, and the parts were assembled as diesel engine mouthpiece parts and tested for temperature and durability. The results showed that the temperature at point B was 600°C and the temperature at point A was 400°C.

The measured temperature at point B, 600° C., is extremely high compared to the temperature at point B, 400° C., of conventional cap parts. In addition, the temperature at point A on the wall near the sub-combustion chamber is 850°C, which is
It was higher than 00℃. From these results, it is confirmed that the temperature difference between points A and B in the cap part of the second embodiment is about half that of the conventional cap part in Examples 1 and 2. Ta. From this result, it can be seen that the thermal stress acting on the cap parts is reduced. Furthermore, since the temperature of the mouthpiece is maintained higher than that of conventional mouthpiece parts, the inner surface of the combustion chamber is maintained at a high temperature. This is expected to improve ignition performance.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a pre-chamber mouthpiece part shown in Embodiment 1 of the present invention, Figure 2 is a bottom view thereof, and Figure 3 is a sectional view of a main part of a diesel engine incorporating the mouthpiece part. . 1... Main body 2... Surface portion 3... Nozzle hole Fig. 1 Fig. 3

Claims (3)

[Claims] (1) A sub-chamber mouthpiece made of ceramics that is fixed between the main combustion chamber and the sub-combustion chamber of a metal cylinder block and has a nozzle hole at the bottom that communicates the main combustion chamber and the sub-combustion chamber, The entire cupboard is formed of a dense ceramic sintered body, and the surface portion including at least a part of the bottom face and a part of the side face, centered on the boundary between the bottom face and the side faces, is formed of a porous ceramic body. A mouthpiece part for a pre-chamber of an internal combustion engine, which is characterized by: (2) The porosity of the ceramic porous body is 10 to 10% by volume.
50% of the base component according to claim 1. (3) The cap component according to claim 1, wherein the ceramic porous body contains reinforcing fibers.