JPH0670369B2 - Secondary combustion chamber of engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary combustion chamber of an engine, and more particularly, to an auxiliary combustion chamber of an engine in which a heat-resistant metal tubular member is fitted to an outer peripheral portion of the auxiliary chamber constituting member. Regarding the auxiliary combustion chamber.

(Prior art) Diesel engine auxiliary combustion chamber (hereinafter referred to as auxiliary chamber)
Is exposed to a high temperature combustion gas of about 1000 ° C and it is desirable to keep it at a high temperature to improve the ignitability. Therefore, recently, the above sub chamber was divided into two parts, one made of a ceramic material having excellent heat resistance and the other made of ceramic material. A sub-chamber constituent member is reinforced, and in order to reinforce its pressure resistance and hold the two-divided sub-chamber constituent member in a regular positional relationship, a heat-resistant metal tubular member is shrink-fitted to the outer peripheral portion of the sub-chamber constituent member. A secondary combustion chamber of an engine is known (see Japanese Utility Model Laid-Open No. 58-175118).

Then, conventionally, the metal tubular member is made of a martensitic heat-resistant steel such as SUS403 which is substantially martensitic structured by quenching, and the tubular member is tempered by a tempering treatment to improve strength and toughness. Organized sorbite into ceramic sub-chamber components at approx. 500-600 ℃
They were fitted by shrink fitting at the temperature of.

(Problems to be solved by the invention) By the way, since the combustion gas temperature in the sub-chamber becomes as high as about 1000 to 1200 ° C., the heat transfer from the sub-chamber constituent members causes the combustion gas temperature to rise to about 500- At 750 ℃, the temperature in the middle part of the tubular member becomes as high as 700-830 ℃.

Since the above temperature is higher than the temperature at the time of shrink fitting, the effect of shrink fitting is almost lost, and for example, as shown in FIG. 3, the middle part of the metal tubular member 105 swells due to thermal expansion, The tightening force for tightening the sub chamber constituent member 104 from the outside becomes extremely weak.

As a result, the edge portion of the mating surface 104a of the sub-chamber constituent member 104 that is divided into the upper and lower parts is damaged, or the relatively thin portion of the middle portion of the sub-chamber constituent member 104 is cracked by the combustion gas pressure. However, there arises a problem that a gap is generated between the mating surfaces 104a.

Even if the sub-chamber constituent members are integrally formed on the upper and lower sides,
There arises a problem that the middle part of the sub chamber constituent member is broken.

(Means for Solving the Problems) The sub-combustion chamber of the engine according to the present invention is made of a ceramic sub-chamber constituting the sub-chamber, and made of metal fitted to the outer peripheral portion of the sub-chamber constituting member. In an auxiliary combustion chamber of an engine provided with a tubular member, the tubular member comprises 0.13 to 0.45% C, 0.3 to 2.5% Si, 0.5 to 1.0% Mn, and 10.0 to 13.0% by weight.
Consists of martensitic heat-resistant steel with a substantially martensitic structure, consisting of Cr, 0.3 to 1.3% of Mo, and Fe that occupies the remainder, and this tubular member is shrink-fitted to the auxiliary chamber constituent member. It is a sorbite structure obtained by post-tempering.

(Operation) Since the auxiliary combustion chamber of the engine according to the present invention is configured as described above, the following operation can be obtained.

First, in relation to the components of the tubular member, 0.3-2.5%
Since it contains Si and 0.5 to 1.0% Mn, it does not become brittle due to improved hardenability.Since it contains 10.0 to 13.0% Cr, heat resistance is improved and the coefficient of thermal expansion is an appropriate value. Becomes 0.
Since it contains 3 to 1.3% of Mo, the hardenability and strength and the creep strength during hot are improved, and temper brittleness is also prevented.

Since the tubular member is substantially made of martensitic heat-resistant steel having a martensitic structure, it can be transformed into a sorbite structure by tempering it.

Then, since the cylindrical member is shrink-fitted to the auxiliary chamber constituent member and tempered after fitting to change from the martensite structure to the sorbite structure, in addition to the tightening force due to the shrink fitting, when the martensite structure is changed to the sorbite structure. A strong tightening force is generated as the metal structure shrinks.

(Effects of the Invention) According to the auxiliary combustion chamber of the engine according to the present invention, as described above, the cylindrical member made of martensite heat-resistant steel having substantially martensite structure is shrink-fitted to the auxiliary chamber constituent member. Post-tempering process changes to sorbite structure, so the contraction of the metal structure when changing from martensite structure to sorbite structure is effectively utilized to significantly strengthen the tightening force of the tubular member on the sub-chamber components, and during actual operation Even in the state where the tubular member is thermally expanded, the auxiliary chamber constituent member can be restrained by a sufficient tightening force to prevent the damage, and the auxiliary combustion chamber can have excellent durability.

(Example) Hereinafter, the example of the present invention is described based on a drawing.

As shown in FIG. 1, the auxiliary combustion chamber 3 is formed in the cylinder head 2 in the following manner at a position facing the vicinity of the outer periphery of the cylinder bore 1 of the diesel engine and a position slightly outside thereof.

That is, the sub-combustion chamber 3 is basically composed of a sub-chamber constituent member 4 which is vertically divided into two parts, and a tubular member 5 fitted to the outer peripheral portion thereof. And the lower end flange-shaped portion 5a of the cylindrical member 5 which is fitted into the substantially cylindrical recess 6 of the cylinder head 2 from below in a state where they are integrally assembled.
Is fitted by fitting the fitting part 6a at the lower end of the recess 6 and the upper end part of the tubular member 5 to the upper fitting part 6b of the recess 6.

A combustion chamber 7 is formed inside the sub chamber constituent member 4,
This combustion chamber 7 has a cylinder bore 1 on the bottom wall of the sub chamber constituent member 4.
A nozzle 8 of the injector 9 is connected to the main combustion chamber in the cylinder bore 1 at an obliquely directed injection port 8 in the center direction, and a fuel injector 9 is obliquely attached to the cylinder head 2 above the recess 6. A glow plug 11 is attached to the combustion chamber 7 through a circular hole 10 in the upper wall of the sub-chamber constituting member 4, and the glow plug 11 is mounted on the engine center side of the fuel injector 9, and the tip portion of the glow plug 11 It penetrates through the circular hole in the upper wall and projects into the combustion chamber 7.

Further, an annular elastic seal member 12 made of stainless steel is interposed between the outer peripheral portion of the upper end of the sub chamber constituent member 4 and the upper wall surface of the concave portion 6 facing the upper peripheral portion, and the collar portion 5a of the tubular member 5 to the tubular portion 5a. A cylindrical heat insulating space 13 is formed on the outer peripheral side of the tubular member 5 along the upper end of the member 5.

The sub chamber constituent member 4 is made of silicon nitride (Si
₃ N ₄ ), the upper half 4a and the lower half 4 for convenience of molding.
It is divided into b and b, which are held by the tubular member 5 in a predetermined positional relationship and reinforced so as to withstand the combustion gas pressure.

The cylindrical member 5 is a sub-chamber constituent member 4a that is divided into upper and lower parts.
・ Maintaining 4b in a predetermined positional relationship and tightening the outer peripheral portion of the sub chamber constituent member 4 with a sufficient contact pressure so as to prevent the ceramic sub chamber constituent member 4 from being damaged by the combustion gas pressure. The temperature distribution of the tubular member 5 during
As shown in the figure, since the temperature becomes high, the tubular member 5
Must be made of heat-resistant steel with excellent strength.

The tubular member 5 is fitted to the outer peripheral portion of the auxiliary chamber constituting member 4 by heating at 500 to 600 ° C. and shrink fitting, but since the tubular member 5 is in a high temperature state above the shrink fitting temperature, it is tightened by shrink fitting. The action is almost lost.

In the present invention, attention is paid to shrinkage of the metal structure when the martensite structure in heat-resistant steel or the like changes to a sorbite structure by tempering, and the tightening force of the tubular member 5 is significantly strengthened.

Therefore, the cylindrical member 5 is made of a martensitic heat-resistant steel, and after the machining is completed, it is quenched to have a substantially martensitic structure, and the cylindrical member 5 having this martensitic structure is lower than the tempering temperature. 500-600
The sorbite is heated to a temperature of ℃ and fitted to the outer peripheral portion of the sub-chamber constituting member 4 by shrink fitting, and finally the cylindrical member 5 having the martensitic structure is heated to a temperature of 750 to 800 ° C. and tempered. It will be changed to the tubular member 5 of the tissue.

However, the tempering process may be performed before the sub-combustion chamber 3 is assembled to the cylinder head 2, but since most of the tubular member 5 is heated to just the tempering temperature when the engine is operating, the tempering process is performed. The sub-combustion chamber 3 may be assembled to the cylinder head 2 before processing, and may be naturally tempered when the engine is operating.

It is desirable that the martensitic heat-resistant steel applied to the tubular member 5 be made of heat-resistant steel containing the components as described in the column of the composition range in Table 1 below.

Those listed in the column of the above-mentioned composition range are 3 in Table 1.
The tubular member 5 was manufactured from various types of martensitic heat-resistant steels and the following tests were performed, and good performance was obtained. Therefore, it was set to cover the composition range of the above three types of heat-resistant steels. is there.

As shown in Table 1 above, hardenability is improved and brittleness is prevented by containing Si and Mn in appropriate amounts, and hardenability, machinability, and high temperature strength are improved and crystal grains are included by containing Ni in appropriate amounts. Is refined, heat resistance is improved by containing an appropriate amount of Cr and the thermal expansion coefficient does not become too large, and promotion of austenization (improvement of hardenability) is achieved by adding an appropriate amount of Mo. Prevention of temper embrittlement and improvement of hot creep strength are achieved, and heat resistance and oxidation resistance are improved by containing an appropriate amount of Nb.
When V is contained in an appropriate amount, the crystal grains are made finer, heat resistance is improved, and red heat embrittlement at a temperature of 500 to 600 ° C. is prevented.

Next, an example of the quenching treatment, the shrink fitting and the tempering treatment performed on the tubular member 5 made of each of the three types of martensitic heat-resistant steels (SUH3, TAF, SUH600) described in FIG. 1 will be described. To do.

The quenching treatment and shrink fitting in the examples are as described in Table 2 below.

The quenching treatment is performed to change the austenite structure of the tubular member 5 into a martensite structure and improve strength and heat resistance.

The tempering treatment after the shrink fitting is performed by changing the martensite structure of the tubular member 5 into a sorbite structure.
This is done to improve the toughness and to strengthen the tightening force of the tubular member 5 to the sub chamber constituent member 4 by the contracting force when the martensite structure is changed to the sorbite structure.

In the case of the above three types of martensitic heat-resistant steels, the tempering temperature when changing from a martensitic structure to a sorbite structure is about 75% higher than that of ordinary carbon steel.
0 to 800 ° C.

As can be seen from the temperature distribution in FIG. 2, in the present embodiment, most of the tubular member 5 other than the upper and lower end portions is heated to the tempering temperature when the engine is operating. Therefore, the tempering treatment of the tubular member 5 was performed.

The measurement results of the contact pressure between the tubular member 5 and the auxiliary chamber constituent member 4 are as shown in Table 3.

As can be seen from Table 3 above, in comparison with the case where the tubular member 5 is simply shrink-fitted, in the case where the tubular member 5 is tempered after the shrink-fitting, the contact pressure of the tubular member 5, namely The tightening force is increased by 65 to 75%. Further, since the sorbite structure changes to a higher temperature portion, the shrinkage rate is large, and the thermal deformation (thermal expansion) of the tubular member 5 is suppressed, and as a result, the entire sub chamber constituent member can be tightened with a uniform force.

In this embodiment, the case where the sub-chamber constituting member 4 is vertically divided into two has been described, but it goes without saying that the tubular member 5 can be similarly applied when the sub-chamber constituting member 4 is integrally formed. .

[Brief description of drawings]

1 and 2 of the drawings show an embodiment of the present invention. FIG. 1 is a vertical cross-sectional view of the structure of the auxiliary combustion chamber of a diesel engine and its surroundings, and FIG. 2 is a cylinder during engine operation. FIG. 3 is a temperature distribution diagram of the members, and FIG. 3 is an explanatory diagram for explaining the deformation of the tubular member in the conventional auxiliary combustion chamber due to thermal expansion. 3 ... Sub combustion chamber, 4 ... Sub chamber constituent member, 5 ... Cylindrical member.

Claims (1)

[Claims] 1. A sub-combustion chamber of an engine, comprising: a ceramic sub-chamber constituting member forming a sub-chamber; and a metal tubular member fitted to an outer peripheral portion of the sub-chamber constituting member. By weight, 0.13 to 0.45% C and 0.3 to 2.5%
Si and 0.5-1.0% Mn and 10.0-13.0% Cr and 0.3-1.3%
Of martensite-based heat-resistant steel that is substantially martensite-structured and consists of Mo and Fe that substantially occupy the remainder. A secondary combustion chamber of the engine characterized by being organized.