JPH0134664Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a heat insulating support structure for a ceramic hot plug that constitutes the lower structure of a pre-chamber provided in a cylinder head of an engine.

[Conventional technology]

Diesel engines for vehicles such as automobiles are
The combustion chamber must have a wide rotation range, high maximum output, smooth rotation, good fuel consumption, and be advantageous in terms of noise.To satisfy these requirements, the combustion chamber is equipped with an auxiliary chamber called a vortex chamber. It has been proposed to provide a

This kind of pre-chamber type diesel engine has a spherical swirl chamber in the cylinder head that communicates with the main combustion chamber, and during the compression stroke, a swirl of air is created in this swirl chamber, and fuel is injected into it for combustion. It is. The conventional swirl chamber was constructed by press-fitting a metal mouthpiece, that is, a hot plug, into a recessed portion of the cylinder head.

However, with the development of ceramic materials in recent years,
Cheap ceramic materials with excellent heat resistance have become available.

[The problem that the idea attempts to solve]

However, although ceramic materials have lower thermal conductivity than metals, even if they are directly attached to the cylinder head, the temperature of the outer peripheral wall of the hot plug will be the same as that of the cylinder head, which is kept at a low temperature, so this will not reduce heat loss. . Furthermore, in this case, there is a risk that the brittle ceramic hot plug may be destroyed due to the difference in thermal expansion coefficient between the metal cylinder head and ceramics, and there is a problem that installation is significantly more difficult than conventional metal ones.

For example, Japanese Utility Model Application No. 58-87928 has been proposed regarding a mounting structure for a ceramic hot plug.
However, this device does not employ the technology of keeping the hot plug at a high temperature by creating a gap fit between the hot plug and the cylinder head to create an insulated structure, and when fixing the hot plug to the cylinder head, the pin I am in the process of typing,
This has the disadvantage that localized stress is likely to occur and the hot plug is likely to be damaged.

The purpose of this invention is to improve heat insulation by fitting the ceramic hot plug that makes up the swirl chamber of a diesel engine to the underside of the cylinder head by fitting it into a recess formed in the cylinder head. The goal is to provide concrete means.

The ceramic hot plug that makes up the lower structure of the pre-chamber is always exposed to high temperatures because it faces the main combustion chamber, but the communication hole that connects the main combustion chamber and the pre-chamber gets particularly hot. Since durability problems occur in this part, it is necessary to preferably have a clearance fit structure so that this part is not pressed against the cylinder head.

Also, it is important to fix this hot plug in the correct direction with respect to the recess formed in the cylinder head, that is, with the communication hole connecting the auxiliary chamber and the main combustion chamber facing the predetermined direction of the main combustion chamber. .

Generally, when fixing a hot plug to a cylinder head, a method is employed in which a metal pin is driven between the cylinder head and the hot plug to fix it, as described above. However, ceramics are brittle, and there is a high possibility that they will easily break due to local stress when a pin is driven or fitted. should be avoided.

This invention provides a support structure for a ceramic hot plug that has excellent durability by being installed without causing local stress, as well as a heat insulating support structure.

[Means to solve the problem]

In order to achieve the above object, in this invention, a groove (stepped part) is provided almost circumferentially at the hem of a ceramic hot plug that is clearance-fitted into a recess formed in the cylinder head to form an auxiliary chamber. A positioning groove surface is preferably formed at the same depth without continuously giving a rapid cross-sectional change to the groove portion, and the positioning member is fixed to the groove surface, and the positioning member is fixed to the cylinder head side. The hot plug support structure is formed by fitting a metal ring around the groove with a gap.

[Effect]

A stepped portion is formed in the circumferential direction of the hem of the ceramic hot plug, and this stepped portion is supported with a gap fit on a metal ring fixed to the cylinder head side, and there is also no gap between it and the cylinder head. Since it has a fitting structure, almost the entire structure constitutes a heat insulating support.

Since the communication hole is the part where combustion gas is ejected into the main combustion chamber, it tends to become hot, and if this part is fixed to the cylinder head side, there is a problem that it will cool down and reduce the combustion effect of the subchamber. However, in this invention, insulation is provided between the stepped portion provided in the circumferential direction of the bottom portion of the hot plug and the annular ring by a clearance fit.

Further, a positioning groove surface is formed by connecting to the stepped portion of the hem, a positioning metal plate is fixed to this groove surface, and the protrusion of this metal plate is fitted into the vertical groove on the cylinder head side. Therefore, the mounting position can be accurately defined, and stress concentration does not occur in the positioning means unlike in conventional devices fixed using pins.

〔Example〕

Embodiments of this invention will be described below with reference to the drawings.

FIG. 1 is a side view of a ceramic hot plug 10 of this invention, and FIGS. 2A and 2B are perspective views looking up from the bottom.

In this invention, a recess 1 that constitutes a swirl chamber inside
1, a groove 15 is formed in the circumferential direction of the hem of the outer peripheral surface 13 of a ceramic hot plug 10 provided with a communication hole 12 connecting the main combustion chamber and the swirl chamber. Support step portions 14 are formed at the corners of the groove portions 15. In this embodiment, the support step 1
4 is formed at the upper edge of the groove portion 15 over almost the entire circumference of the hot plug 10.

As shown in FIGS. 2A and 2B, the outer circumferential surface 13 that is farthest from the main combustion chamber side opening 17 of the communication hole 12 opened on the lower surface of the hot plug 10
A positioning groove surface 16 is provided at the same depth as the groove portion 15 and continuous without any step. A mounting surface 9a of a metal plate 9 having a protrusion 9a facing outward and fitting into the vertical groove on the cylinder head side is attached to this positioning groove surface 16 by adhesive.

FIG. 3 is a perspective view of an embodiment of the metal ring 20 of the support member which is fit into the groove 15 of the hot plug 10, and the inner circumference D thereof is formed to be slightly larger than the outer circumference diameter of the groove 15. There is.

The hot plug 10 constructed as described above is fitted into the recess 6 formed in the cylinder head 1 as shown in FIGS.
It is supported in a clearance fit by metal rings 20 fixed to the sides to form the swirl chamber 4 of the diesel engine.

That is, the swirl chamber recess 6 of the cylinder head 1
The hot plug mounting portion 7 of the hot plug 1 is
While forming it slightly larger than the outer peripheral diameter of 0,
An annular groove 8 having a diameter slightly smaller than the outer diameter E of the metal ring 20 is formed in the cylinder head 1. In addition, the hot plug mounting portion 7 has a longitudinal groove 7a in the cylinder head 1 for preventing the hot plug 10 from rotating, and a protrusion 9 on the metal plate 9.
Drill a hole slightly larger than this to match the shape of a.

First, a seal gasket 5 is interposed on the ceiling surface of the hot plug mounting section 7, and the hot plug 10 is inserted into the vertical groove 7a by the protrusion 9 of the metal plate 9.
Insert the hot plug 10 along line a, and then press fit the metal ring 20 into the annular groove 8. At this time, the metal ring 20 and the lower surface 1a of the cylinder head
Make sure that the surface positions are almost the same. In addition,
For the seal gasket 5, a ring-shaped metal elastic member with a U-shaped cross section is used in this embodiment. In addition to this type of seal gasket 5, those having an S-shaped cross section or a dish-shaped cross section are also used.

Therefore, in the hot plug support structure of this invention constructed as described above, the hot plug 10 has its outer peripheral surface 13 connected to the hot plug mounting portion 7 of the cylinder head 1, as shown in FIGS.
and the metal ring 20 are in a clearance fit state,
Its upper surface 18 is in close contact with the seal gasket 5. Furthermore, the support step 14 is pressed against the metal ring 20 by the elastic force of the seal gasket 5, and the groove 15 is in a clearance fit with the metal ring 20.

In this state, the lower surface 19 of the hot plug 10 may be on the same plane as the metal ring 20, or may be located inside or protrude from the lower surface 1a of the cylinder head 1 if only slightly.

As shown in FIG. 6, the hot plug 10 supported on the cylinder head 1 as described above is firmly connected to the cylinder block 24 and the head bolts 25 via the cylinder head gasket 23. 23 supports the lower surface 19 of the hot plug 10, the seal gasket 5 contracts slightly, so the support step 14 of the hot plug 10 rises slightly from the upper surface of the metal ring 20, and the sealing force of the seal gasket 5 further increases. At the same time, there is no collision between the support step 14 and the metal ring 20 due to engine vibration, and damage to the support step 14 is eliminated.

Therefore, in the hot plug support structure of this invention, the hot plug 10 is attached to the hot plug 10 with the engine assembled and the main combustion chamber 29 formed.
It is possible to create a so-called floating state in which the cylinder head 1 does not come into close contact with the cylinder head 1 except for the upper surface 18 of the cylinder head 1. Further, even if contact occurs, it is limited to a small portion of the outer circumferential surface 13 of the hot plug 10.

FIG. 7 shows a second embodiment of the hot plug support structure of this invention, in which the hot plug 1 inserted into the hot plug mounting portion 7 of the cylinder head 1
A discontinuous portion 8a is provided in the annular groove 8 forming the support step portion 14 of 0, and a groove portion 20a that engages with the discontinuous portion 8a is also provided on the metal ring 20 side. This is done using the ring 20 itself.

8, 9, and 10 are a bottom view, a perspective view seen from below, and a cross-sectional view showing the installed state of a hot plug 10' showing a third embodiment of the invention. Hot plug 1 of embodiment 1
Parts that are the same as 0 are indicated using the same symbols.

In this embodiment, the opening side of the communicating hole 12 of the groove 15 for supporting the hot plug provided at the bottom of the outer circumferential surface 13 of the hot plug 10' is directed upward as shown in FIG. The groove 26 is extended to form a heat insulating groove 26.

In this embodiment, the depth of the heat insulating groove 26 is the same as the depth of the support groove 15, but it may be slightly deeper. In addition, this heat insulation groove portion 26
As indicated by diagonal lines in FIG.
In this embodiment, the tangent line M drawn from the center line C of the hot plug 10' toward both side edges of the communication hole 12, N range L (approximately 120°)
It is set to .

The upper end 26a of the heat insulating groove 26 is located above the bottom wall 4a of the vortex chamber, and the heat insulating groove 26 is located on the back surface of the protrusion 27.

FIG. 10 shows how the swirl chamber 4 is formed in the cylinder head 1 using the hot plug 10' constructed as described above.

As can be seen from this figure, when the hot plug 10' of this embodiment is installed in the swirl chamber recess 6 of the cylinder head 1, the outer periphery of the hot plug 10' on the rear side of the protrusion 27 is formed by the heat insulating groove 26. A heat insulating space H between the surface 13 and the cylinder head 1
will be formed.

In the first embodiment shown in FIGS. 4 to 6, the outer peripheral surface 13 of the hot plug 10 and the hot plug mounting portion 7 of the cylinder head 1 are provided with a clearance fit, and the metal ring 20 is provided with a clearance fit in the groove portion 15. Although heat loss is reduced by forming a heat insulating layer, in this embodiment, the heat of the hot plug 10' on the back side of the protrusion 27 is transferred to the cylinder head 1 by the action of the heat insulating layer H. This prevents the temperature from escaping to the side, preventing a drop in temperature on the back side.

As a result, the hot plug 10' of this embodiment
Since the temperature gradient between the temperature of the protrusion 27 sandwiched between the communication hole 12 and the bottom wall 4a of the swirl chamber 4 and the heat insulating groove 26, which is particularly high in temperature, can be made gentle, the protrusion of the ceramic hot plug 10' This prevents damage such as cracks from occurring due to the thermal gradient in the vicinity of the portion 27, and this protruding portion 27 is maintained at a higher temperature, changing the combustion pattern, reducing engine noise and improving thermal efficiency. .

[Effect of idea]

This idea is based on the recess 6 formed in the cylinder head.
A groove 15 is formed almost circumferentially at the bottom of the ceramic hot plug 10 which is fitted with a clearance to form a swirl chamber (auxiliary chamber), and a rapid cross-sectional change is continuously given to the groove 15. A positioning groove surface 16 is formed without any interference, and a positioning member 9 is attached to the groove surface 16.
This is a hot plug support structure in which a metal plate (metal plate) is fixed and a metal ring 20 fixed to the cylinder head 1 side is fitted around the groove 15 with a gap.

Therefore, the circumferential surface of the hot plugs 10, 10' is
There is a clearance fit between the hot plug mounting portion 7 formed in the cylinder head 1 and the inner surface of the metal ring 20 fixed in the annular groove 8 provided on the main combustion chamber side, so that the hot plugs 10, 10' can be attached to the cylinder head. 1, it is supported in a floating state, and good heat insulation can be achieved.

A positioning groove surface 16 is formed by connecting to the groove 15 formed at the bottom of the hot plug 10, 10' so as not to cause a sudden change in cross section.
Since a positioning member such as a metal plate 9 is attached within the hot plug 6, there is no possibility of locally generating high stress and damaging the hot plug, unlike the conventional fixing using pins.

[Brief explanation of drawings]

Figures 1 to 6 show the first embodiment of this invention, with Figure 1 being a side view of the hot plug, and Figures 2 A and B looking up from both sides of the hot plug shown in Figure 1. FIG. 3 is a perspective view of a metal ring that is a support member used in this invention, FIG. 4 is a sectional view showing the support structure of the hot plug of this invention, and FIG.
FIG. 6 is a cross-sectional view of the main parts of an engine employing the hot plug support structure of this invention. FIG. 7 is a perspective view showing the structure of a second embodiment of this invention. 8 to 10 show a third embodiment of the invention, in which FIG. 8 is a bottom view of the hot plug, and FIG. 9 is a perspective view of the hot plug shown in FIG. 8 as viewed from the direction of arrow B. FIG. 10 is a sectional view of a swirl chamber using the hot plug. 1...Cylinder head, 4...Swirl chamber, 4a...
... Bottom wall, 5 ... Seal gasket, 6 ... vortex chamber recess, 7 ... Hot plug attachment part, 7a ... Vertical groove, 8 ... Annular groove, 9 ... Metal plate (positioning member), 10 ... ... Hot plug, 14 ... Support step, 15 ... Groove, 16 ... Positioning groove surface,
20...Metal ring, 27...Protrusion.

Claims (1)

[Scope of utility model registration request] A groove is formed almost circumferentially in the hem of a ceramic hot plug that is loosely fitted into a recess formed in a cylinder head to form an auxiliary chamber, and a rapid cross-sectional change is continuously given to the groove. A support structure for a hot plug, which is formed by forming a positioning groove surface, fixing a positioning member to the groove surface, and fitting a metal ring fixed to the cylinder head side around the groove with a gap.