JPH0532728U - Mounting structure for hot plug of internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent cracks from occurring in the hot part of the cylinder head due to expansion and thermal deformation of the hot plug. [Structure] A part of the bottom surface of the hot plug 2 is exposed inside the combustion chamber 8, and the remaining part is in contact with the gasket 13 for sealing, and the part in contact with the gasket 13 is inserted in the hot plug fitting hole 7. A gap 9 is formed to allow the hot plug 2 to expand, and this gap 9 is formed in the cylinder bore 10.
A structure for mounting a hot plug of an internal combustion engine, which is reduced so as not to communicate with the cylinder bore 10 at a position in contact with the cylinder bore 10.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention mainly relates to a hot plug mounting structure for an internal combustion engine, which absorbs thermal expansion and thermal deformation without causing a dead volume of a hot plug provided in a combustion chamber of a diesel engine or the like.

[0002]

[Prior Art]

 In recent years, internal combustion engines have tended to have higher output due to the installation of turbochargers, etc., but instead of obtaining higher output, they are accompanied by an increase in fuel consumption and higher pressure in the cylinder. However, the combustion temperature is becoming higher, and in terms of cost, the same cylinder body and cylinder head are used, and the displacement is changed to increase engine variations.

Under such circumstances, the internal combustion engine is required to operate under severe conditions in terms of its durability. On the other hand, a hot plug fitting hole 7 for inserting the hot plug 2 of the diesel engine as shown in FIG. 8 is formed on the lower surface of the cylinder head 4, and the hot plug 2 is inserted from the lower surface of the cylinder head 4. The structure is such that the combustion chamber 8 shown in FIG. 9 is formed.

Since the material of the cylinder head 4 is mainly aluminum or cast iron today, the support structure of the hot plug is a big problem in terms of durability performance. In particular, the cylinder head 4 made of aluminum is used. Many problems occur in the case of the internal combustion engine. That is, as shown in FIG. 10 showing the state in which the hot plug 2 is removed, the hot plug fitting hole 7 near the nozzle hole 2A of the hot plug 2 through which the gas that has exploded and burned in the combustion chamber 8 is jetted into the cylinder, and the cylinder. A crack 6 communicating with the head 4 is generated, and this crack 6 progresses and finally reaches the water jacket of the cylinder head 4, and the piston 1 reciprocates to cool in the cylinder bore in the cylinder body 5. This will cause serious troubles for internal combustion engines, such as water intrusion and damage.

The cause of the crack 6 is that the hot plug 2 made of metal expands due to the high temperature generated at the time of combustion during high speed and high load operation of the diesel engine. The plug is pushing the fitting hole 7 outward strongly. Considering the state of the material of the cylinder head 4 itself in such a state, the temperature near the injection hole 2A of the hot plug 2 indicated by the portion A in FIG. The temperature of the portion B located on the outer peripheral portion of the cylinder bore is much lower, and the combustion temperature rise during high-speed, high-load operation causes the material of the cylinder head 4 near the portion A to become soft. Under these circumstances, the hot plug 2 which is heated to the combustion temperature and expanded expands the softened part A than the hot plug hole 7, and the crack 6 is generated.

Furthermore, when using a diesel engine, the thermal deformation stress generated in the cylinder head 4 causes the crack 6 to grow due to repeated high-speed / high-load operation, low-speed / low-load operation, and stop. It will accelerate. As shown in FIG. 8, generally, the hot plug 2 that forms the combustion chamber 8 provided in the cylinder head 4 is configured so that the flange portion 2B is integrated with the lower surface of the cylinder head 4. A hot plug fitting hole 7 is provided in the cylinder 4, and a head gasket 13 is interposed between the cylinder head 4 and the cylinder body 5 on the outer periphery of the cylinder bore for sealing.

On the other hand, a concavity for a swirl chamber is formed on the inner wall surface of the cylinder head, and a die for separating the swirl chamber from the main combustion chamber is inserted into the concavity, and a nozzle is formed in the die. In a diesel engine with a swirl chamber, the outer diameter of the outer wall surface of the insert of the mouthpiece at room temperature is smaller than the inner diameter for mounting the recess for the swirl chamber by an amount equivalent to the thermal expansion during engine operation. The invention of Japanese Patent Laid-Open No. 56-104115 relating to the swirl chamber structure has been proposed.

That is, in the above-mentioned known technique, the gap 20 is formed around the hot plug 2 shown in FIG. 8 as shown in FIG. 11, and the gap 20 is formed between the cylinder head 4 and the cylinder body 5 shown in FIG. Since it is not possible to seal with the method in which the head gasket 13 is provided, the gap portion 20 forms a dead volume. Further, in order to prevent the head gasket 13 from contacting a part of the bottom surface of the hot plug 2, as shown in FIG. 12, it is necessary to adopt a shape in which the ring-shaped gap 20 is exposed in the combustion chamber 8. I won't get it. In this case, the means for fixing the hot plug 2 to the cylinder head 4 becomes difficult, and in this shape, the bottom surface of the collar portion 2B and the surrounding area are heated, so that the hot plug 2 and the portion forming the surrounding area are heated. As the temperature rises, the cylinder head is likely to be deformed or cracked due to heat, and moreover, a large amount of the gap 20 becomes a dead volume, resulting in poor combustion and adversely affecting the output surface, smoke surface, and emission surface. Will affect.

The present invention provides a hot plug support that does not cause serious damage to the internal combustion engine by causing cracks in the hot part of the cylinder head due to expansion and thermal deformation of the hot plug provided in the cylinder head. It provides the structure.

[0010]

[Means for Solving the Problems]

 The hot plug mounting structure for an internal combustion engine according to the present invention for solving the above problems is such that a part of the bottom surface of the hot plug is exposed inside the combustion chamber and the rest is in contact with the gasket for sealing. The hot plug fitting hole of the part that contacts with is formed with a gap that allows thermal expansion of this hot plug, and this gap is reduced so that it does not communicate with the cylinder bore at the position where it contacts the cylinder bore. It has a feature.

[0011]

[Work]

 The hot plug exposed to the high temperature in the combustion chamber expands in a direction away from the combustion chamber, and the hot plug softened at the high temperature does not strongly press the fitting hole portion, so that cracking of the cylinder head can be prevented.

[0012]

【Example】

 Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 7, which is provided on the lower surface of the cylinder head 4 similar to the conventional example of FIG. 8 and has the same parts as those of the conventional example of FIG. Are denoted by the same reference numerals. First, in the first embodiment shown in FIG. 2 which is a vertical cross-sectional view of FIG. 1 and a plan view of FIG. 1 seen from below, the hot plug fitting hole 7 formed in the cylinder head 4 has a temperature lower than that of the cylinder bore 10 having a relatively low temperature. At a distant outer peripheral position, that is, at a portion where the head gasket 13 contacts the lower surface, a gap portion 9 for absorbing expansion and thermal deformation of the hot plug 2 due to heat and a portion where the main body of the hot plug 2 is fitted and a collar. It is provided on both of the parts where the parts 2B are fitted. As shown in FIG. 2, the gap 9 has a crescent shape, and the portion farthest from the cylinder bore 10 is the widest, and there is almost no near portion, so that the combustion gas does not enter the gap 9 or only slightly penetrates. Is considered.

By providing a crescent-shaped gap 9 at a position apart from the cylinder bore 10 in a part of the periphery of the hot plug 2 described above, the internal combustion engine operates at high speed and high load, and is close to the nozzle hole 2A. When the hot plug 2 becomes hot and expands or is thermally deformed by heat, the hot plug 2 will not be formed in the gap 9 on the low temperature side as shown in the vertical sectional view of FIG. 3 and the plan view of FIG. As a result, the expanded portion is absorbed by the gap portion 9. Therefore, it is necessary that the gap 9 has a cross-sectional shape suitable for absorbing the expansion of the hot plug 2.

Next, in the second embodiment of FIG. 5, the gap 9 is provided only in the portion of the hot plug fitting hole 7 at the outer peripheral position of the cylinder bore, which faces the flange portion 2B of the hot plug 2. The gap 9 can absorb the thermal expansion of the collar portion 2B, which has the highest temperature among them. Even in this case, a slight gap can be formed in the main body of the hot plug 2.

In Embodiment 2 of FIG. 6, a gap 9 is provided at the outer peripheral position of the cylinder bore of the hot plug fitting hole 7 into which the hot plug 2 having no flange 2B is inserted. In this case as well, it acts so as to absorb the thermal expansion portion as described above. In each of the embodiments of the present invention as described above, the positioning when the hot plug 2 is inserted and assembled from the lower surface side of the cylinder head 4 is performed by inserting the hot plug 2 as shown in FIGS. 2 and 7. There is no problem because it is determined by the positions of the contacts C, A, D between the peripheral surface of the hole 7 and the surface of the hot plug 2. If desired, the hot plug 2 can be positioned by interposing a fixing pin between the cylinder head 4 and the hot plug 2.

[0016]

[Effect of the device]

 According to the hot plug mounting structure of the internal combustion engine of the present invention, a part of the bottom surface of the hot plug is exposed inside the combustion chamber, and the remaining part is in contact with the gasket to seal the hot plug. The plug has a fitting hole formed with a gap allowing thermal expansion of the hot plug, and the gap is reduced in size so as not to communicate with the cylinder bore at a position in contact with the cylinder bore.

Therefore, the amount of thermal expansion and thermal deformation of the hot plug during high-speed / high-load operation of the engine is absorbed by the gap provided at the outer peripheral position of the cylinder bore on the relatively low temperature side of the cylinder head, and immediately the recessed portion. As a result, the problem that the material near the nozzle hole of the hot plug of the cylinder head becomes the highest temperature and destroys and cracks can be prevented, which causes a serious malfunction in the internal combustion engine. Will disappear.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a main part of a hot plug insertion portion of an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a plan view seen from below in FIG.

FIG. 3 is a vertical cross-sectional view of an essential part showing a state where the hot plug of FIG. 1 has expanded.

FIG. 4 is a plan view seen from below in FIG.

FIG. 5 is a vertical cross-sectional view of a main part of a hot plug insertion portion according to a second embodiment of the present invention.

FIG. 6 is a plan view of a main part of a hot plug insertion portion according to a third embodiment of the present invention as viewed from below.

FIG. 7 is a plan view showing a positioning contact at the time of assembling a hot plug according to each embodiment of the present invention.

FIG. 8 is a vertical cross-sectional view of a main part around a combustion chamber of an internal combustion engine having a conventional hot plug.

9 is a plan view of a main part of a cylinder head of the internal combustion engine of FIG. 8 viewed from below.

10 is an enlarged plan view of an essential part showing a state in which a crack has occurred in the cylinder head of FIG. 9.

FIG. 11 is a plan view of a main part of another conventional cylinder head as viewed from below.

FIG. 12 is a plan view of a main part of a cylinder head of another conventional example.

[Explanation of symbols]

2 Hot plug 2B Fitting collar 4 Cylinder head 7 Hot plug fitting hole 9 Gap 10 Cylinder bore 13 Head gasket.

Claims (1)

[Scope of utility model registration request] 1. A part of the bottom surface of the hot plug is exposed inside the combustion chamber, and the rest is in contact with the gasket for sealing. The hot plug fitting hole of the part in contact with the gasket expands the thermal expansion of the hot plug. A mounting structure for a hot plug of an internal combustion engine, in which a gap portion is formed so as to allow the internal combustion engine to be communicated with the cylinder bore.