JPH0531210Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to an engine pre-chamber structure formed using a cylindrical ceramic member.

(Prior Art) Recently, attempts have been made to form the pre-chamber of the engine using a ceramic material having excellent heat insulation and heat resistance. However, ceramic materials generally have a low tensile strength of about 1/10 of the compressive strength, and are easily damaged by repeated thermal tensile stress due to thermal shock or mechanical vibration, resulting in poor durability (low Weibull coefficient). . For this reason, in order to suppress the tensile stress caused by the thermal shock and improve the durability of the ceramic members that form the subchamber of the engine, for example, as shown in Fig. 2, stainless steel with excellent heat resistance is used. for example
A pair of ceramic members 21a and 21b that can divide the cylindrical metal ring 20 made of SUS430 into upper and lower parts.
A heat insulating space 22 is formed around the metal ring 20 in order to apply compressive stress to the outer periphery of the metal ring 20 by shrink fitting, and further improve engine performance by utilizing the heat resistance properties of the ceramic material itself. Structures that do this have been proposed in the past (for example, by
58-175118).

However, such ceramic members 21a,
21b is fitted and integrated with a cylindrical metal ring 20, and is fitted into the pre-chamber forming recess 24 of the cylinder head 23 as shown in FIG.
5, the following problems arise.

That is, first, when the ceramic members 21a, 21b become high in temperature due to the continuation of the combustion state in the auxiliary chamber 25, the shrink-fitted metal ring 20 itself also becomes high in temperature and thermally expands. However, since the metal ring 20 is substantially restrained from deformation toward both the upper and lower ends, compressive stress is generated in the axial direction, and because the deformation inward is restrained by the ceramic members 21a and 21b. , the compressive stress eventually increases to the metal ring 2 as shown by the arrow in the same figure.
0 toward the outside, and ultimately causes thermal deformation toward the outside (towards the heat insulating space 22) as shown by the imaginary line in FIG. As a result, the clamping force against the pair of ceramic members 21a and 21b is greatly reduced, and furthermore, when the ceramic member is composed of upper and lower members joined at the center as shown in FIG. Misalignment occurs between the ceramic members 21a and 21b, and high-temperature combustion gas leaks from the seam, impairing the durability of the metal ring 20.

Furthermore, if the pair of ceramic members 21a, 21b shift from each other and move, chipping is likely to occur at the joint.

(Purpose of the invention) The present invention was made based on the above-mentioned circumstances, and the shape of the metal ring is made into a medium-thin shape that gradually becomes thicker outward from the center to both ends. At the same time, by sandwiching the metal ring between the cylinder head and the cylinder block to substantially restrain thermal deformation of the metal ring in the axial direction, the deformation of the metal ring when the thermal stress occurs is suppressed. It is an object of the present invention to provide a pre-chamber structure for an engine that solves the above-mentioned problems by applying force inward.

(Means for Achieving the Object) In order to achieve the above object, the present invention has a heat insulating sub-chamber member fitted in a sub-chamber forming recess of a cylinder head. It is formed of a pair of cylindrical ceramic members with a split structure, and is integrated by shrink-fitting a metal ring to the outer periphery of the pair of upper and lower ceramic members, and is fitted into the sub-chamber forming recess of the cylinder head. In an engine pre-chamber structure in which a heat insulating space is formed between a metal ring and the cylinder head, the metal ring to be shrink-fitted has a thinner wall in the center over the entire axial direction and gradually becomes thinner toward both ends. The metal ring is formed into a medium-thin shape with a thick wall on the outside, and the metal ring is sandwiched between the cylinder head and the cylinder block to substantially restrain thermal deformation of the metal ring in the axial direction. be.

(Function) According to the above means, the metal ring shrink-fitted to the outer periphery of the pair of upper and lower ceramic members forming the subchamber is thin-walled in the center and thin-walled toward the outer side toward both ends. It has a medium-thin shape that gradually becomes thicker, and its thermal deformation in the axial direction is substantially restrained, so the deformation force due to thermal stress is restrained at both the upper and lower ends and concentrated in the center. acts inward of the metal ring, and as a result, the clamping force against the pair of upper and lower ceramic members joined at the center increases, and the misalignment between the pair of upper and lower ceramic members increases. will no longer occur.

(Example) Hereinafter, a pre-chamber structure of an engine according to an example of the present invention will be described in detail with reference to FIG. 1 of the drawings.

First, as shown in FIG. 1, the sub-chamber structure of the engine in this embodiment is fitted into the sub-chamber forming recess 11 of the cylinder head 1 of the diesel engine.
The metal ring 7 is attached to the outer peripheral portions 8a and 9a by shrink fitting.
A pre-chamber member 6 is formed by a pair of cylindrical heat-resistant ceramic members 8 and 9 made of silicon nitride (Si ₃ N ₄ ) etc. that can be divided into upper and lower parts, and the metal ring 7 It has a heat insulating space 15 formed between the outer peripheral surface 7d and the inner peripheral surface 11a of the recess 11 of the cylinder head 1.
The ceramic members 8 and 9, which serve as chamber members forming the auxiliary chamber, are joined to a substantially central horizontal plane of the auxiliary chamber 5 to be formed. The top wall 8b of the upper ceramic member 8 has an insertion hole 13 for the glow plug 10 and a fuel injection nozzle 12.
An injected fuel introduction hole 19 is formed in the bottom wall 9b of the lower ceramic member 9, and a nozzle hole 4 is formed obliquely with respect to the main combustion chamber 3 so as to generate a swirling gas flow. There is.

Further, a ring-shaped seal member 1 is provided between the upper wall surface 11b of the recess 11 of the cylinder head 1 and the shoulder annular surface 8c of the upper ceramic member 8.
4 is fitted.

The metal ring 7 to be shrink-fitted is, for example,
Made of stainless steel such as SUS430 or heat-resistant alloy,
By shrink-fitting the upper ceramic member 8 and the lower ceramic member 9, a tightening force is applied to the two members to maintain them in an integrally joined state, and the thermal shock resistance is improved. It is something.

The metal ring 7 is formed to have a thin wall at the center over the entire axial direction, and a tapered shape that gradually becomes thicker toward the outside toward both upper and lower ends. is an arched arc surface, and this arc surface forms the heat insulating space 15, while its upper end 7e is fixed by abutting against the outer circumferential step 11c of the upper end surface of the recess of the cylinder head 1. and the other lower end 7
b A flange portion 7c is formed on the outer peripheral surface, and this flange portion 7c fits into the recess 11 of the cylinder head 1.
The lower end portion 7b is fitted into the stepped portion 11d of the lower end surface.
Most of the side surfaces are located on the cylinder block 16 via the gasket 17.

Therefore, at both the upper and lower ends of the metal ring 7, thermal deformation in the upward, downward, and lateral directions is substantially restrained due to the above-mentioned fitted state, while thermal stress in the thin walled portion in the center acting from both the upper and lower ends is suppressed. Due to the arched outer circumferential surface, the deformation force acts in the direction of the central axis of the metal ring 7, as shown by the imaginary line in FIG.
This will further increase the fitting and tightening force for 9.
Therefore, misalignment between the ceramic members 8 and 9 will not occur.

Note that 18 is a positioning ball.

(Effects of the Invention) As explained above, the present invention provides an insulating sub-chamber member fitted into the sub-chamber forming recess of the cylinder head, which is connected to a pair of upper and lower divided cylinders joined at the center. A metal ring is shrink-fitted to the outer periphery of the pair of upper and lower ceramic members to be integrated and fit into the auxiliary chamber forming recess of the cylinder head, and the metal ring and the cylinder head are integrated. In an engine pre-chamber structure in which a heat insulating space is formed between the metal rings, the metal ring to be shrink-fitted has a thin wall at the center and gradually thickens outward toward both ends of the metal ring. In addition, the metal ring is sandwiched between the cylinder head and the cylinder block to substantially restrain thermal deformation of the metal ring in the axial direction.

Therefore, according to the present invention, the metal ring shrink-fitted to the pair of upper and lower ceramic members has a tapered shape that is thin in the center and gradually thickens outward toward both ends throughout the entire axial direction. Therefore, the deformation force due to the thermal stress that is restrained at both the upper and lower ends and concentrated in the center acts inward on the metal ring, and the pair of upper and lower ceramics bonded at the center. The tightening force against the members is improved, and there is no possibility of misalignment between the pair of upper and lower ceramic members.

Furthermore, with the above structure, there is no need to use a special heat-resistant, low-expansion material for the material of the metal ring itself, resulting in lower costs.

Moreover, as a result of the above, the shrink-fitting allowance during shrink-fitting can be reduced, and workability is also improved.

Furthermore, since the central portion is thin, the rigidity is low (it easily deforms inward), and the thermal stress applied by the restraint at both ends can be effectively absorbed in this portion.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a pre-chamber structure of an engine according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a conventional sub-chamber structure of an engine. 1... Cylinder head, 3... Main combustion chamber, 4...
...Nozzle hole, 5... Sub-chamber, 6... Sub-chamber chamber member, 7... Metal ring, 8... Ceramic member (upper part), 9... Ceramic member (lower part), 11...
...Concavity for forming sub-chamber, 15...Insulating space.

Claims (1)

[Scope of utility model registration request] The insulating sub-chamber chamber member fitted into the sub-chamber forming recess of the cylinder head is formed of a pair of cylindrical ceramic members with an upper and lower split structure joined at the center, and the outer periphery of the pair of upper and lower ceramic members is In the sub-chamber structure of an engine, the metal ring is integrated by shrink-fitting into the sub-chamber forming recess of the cylinder head, and a heat insulating space is formed between the metal ring and the cylinder head, The metal ring to be shrunk-fitted is made into a tapered shape that is thin in the center and gradually thickens outward toward both ends throughout the entire axial direction, and the metal ring is attached to the cylinder head. and a cylinder block to substantially restrain thermal deformation of the metal ring in the axial direction.