JPH0868328A - Structure of piston with combustion chamber - Google Patents

Abstract

PURPOSE: To fix a combustion chamber structure and a piston main body to each other without any looseness by raising up the heat insulating degree of a combustion chamber formed in a combustion chamber structure, and absorbing a differential thermal expansion between a metal made piston main body and a heat resistance material made combustion chamber structure by the installing ring which is the nearly same maternal as that of the piston main body, in the structure of a piston having a combustion chamber. CONSTITUTION: A metal material made piston main body 1 having a cavity 8 is arranged, and also a heat resistance high temperature and high reinforcing material made combustion chamber structure 3 is arranged on the cavity 8 through a heat insulating air layer 15. In the combustion chamber structure, an auxiliary chamber 2 is formed on the nearly center part of a piston, and a nozzle inserting hole 9 and a connecting hole 10 are formed. An installing ring 6 made of the same material as that of the piston main body 1 is melted and fit to the piston main body 1, and the combustion chamber structure 3 is push-pressed and fixed on the cavity 8 of the piston main body 1 by the installing ring 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a piston having a combustion chamber in which a combustion chamber structure is arranged in a cavity of a piston body.

[0002]

2. Description of the Related Art Conventionally, with respect to a piston, the outer periphery of a ceramic crown having a cavity is fitted in the head portion of a cylindrical aluminum skirt, and a plastic fluid material is interposed in the gap between the outer periphery of the ceramic crown and the head portion. It is known that a piston in which a ceramic crown and an aluminum skirt are joined by heating and pressing a plastic fluid material to deform it,
A cast iron ring was made to coexist with a plastic fluid material in the gap between the outer periphery of the combustion chamber and the head portion (Shokai Sho 62-93141).
(See the official gazette).

[0003] Further, Japanese Patent Application No. 5-5, filed by the present applicant.
No. 46175 discloses a subchamber engine. The sub-chamber engine includes a sub-combustion chamber formed in a piston head, a main combustion chamber formed on a cylinder side, a communication port formed in the piston head for communicating the main combustion chamber with the sub-combustion chamber, and It has a fuel injection nozzle for injecting fuel into the sub-combustion chamber, the fuel injection nozzle is disposed in the cylinder head, and can penetrate into the central communication port formed in the piston head near the piston top dead center, and the communication port is the above-mentioned. A plurality of them are formed spaced apart from the center of the auxiliary combustion chamber in the circumferential direction, and the inflow direction into the auxiliary combustion chamber with respect to the cylinder axis is formed obliquely in the circumferential direction in the direction opposite to the swirl flow of the main combustion chamber. The jet direction from the sub combustion chamber to the main combustion chamber is formed in the swirl flow direction of the main combustion chamber.

[0004]

To the 0005] Generally, the combustion temperature in the secondary chamber because of the high temperature, as a measure to reduce the production of NO _X, it is effective to combust the fuel-rich.
When the combustion temperature is high, it is effective to use a sub-chamber engine as a type of engine structure in order to burn the fuel rich. When the engine is configured as a sub-chamber combustion chamber, in order to increase the combustion speed of the sub-chamber combustion chamber to the same level as the combustion speed of the direct injection combustion chamber, a communication hole that connects the sub-chamber to the main chamber It is necessary to increase the cross-sectional area of the passage.

In the conventional swirl chamber type engine, if the direction of the swirl formed in the swirl chamber, the direction of spray from the injection nozzle and the injection timing of fuel from the injection nozzle do not match, NO
There is a problem that the generation of _X and smoke increases. Further, in the swirl chamber engine, since the communication port that communicates the sub chamber and the main chamber is small, throttling loss occurs due to the communication port,
This will cause a reduction in engine output. Generally, since the communication port that connects the main chamber and the sub chamber is provided on the outer peripheral portion of the cylinder, the distance that the jet flow must reach becomes long, and the mixing with the air in the main chamber becomes insufficient. It becomes a cause of generation of HC and smoke.

Therefore, in the sub-chamber engine, the sub-chamber is provided in the center of the cylinder, a plurality of communication holes are provided to connect the main chamber on the cylinder side and the sub-chamber, and the energy ejected from the sub-chamber to the main chamber through the communication holes is increased. It is conceivable to increase the overall passage cross-sectional area of the communication hole and reduce the throttling loss due to the communication hole without reducing However, when the sub chamber is formed in the substantially central portion of the cylinder of the cylinder head, there is a problem that the area formed by the intake and exhaust ports becomes small.
In order to solve this point, it is conceivable to construct a sub chamber in the piston in the sub chamber engine. When the sub chamber is formed in the piston, heat radiation from the sub chamber becomes a problem, so a heat shield type sub chamber engine can be considered.

Regarding the structure of a piston having a combustion chamber, when the combustion chamber structure forming the combustion chamber is attached to the cavity formed in the piston body, the combustion chamber is made when the piston body is made of Al alloy or cast iron. It is preferable that the structure is made of a heat-resistant high-temperature high-strength material. In that case, how strong the combustion chamber structure is formed in the piston body and the thermal energy from the combustion chamber formed in the combustion chamber structure The issue was whether to fix the heat dissipation in the state of reducing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems. A combustion chamber is formed on the piston side to make the cylinder head have a simple structure, a large intake / exhaust port is formed, and an intake / exhaust port is formed. It is possible to form a plurality of cylinders, and in particular, a cavity is formed in the piston body, and a combustion chamber structure in which a combustion chamber is formed through a heat shield air layer is arranged in the cavity. The piston body is made of almost the same material as the piston body, absorbs thermal expansion, and is firmly fixed without rattling, suppressing heat dissipation from the combustion chamber to the piston body, facilitating assembly and reducing the heat capacity of the combustion chamber structure. To provide a structure of a piston having a combustion chamber attached to the structure.

[0009]

The present invention is configured as follows to achieve the above object. That is, the present invention is directed to a piston main body made of a metal material having a cavity formed in the piston, and a combustion chamber structure made of a heat-resistant high-temperature high-strength material forming a combustion chamber arranged in the cavity with a heat-shielding air layer in the piston. And a piston in which a part of the outer circumference is joined to the piston main body by a joining portion to lock the combustion chamber structure inside the cavity by locking the combustion chamber structure inside the cavity. The present invention relates to a structure of a piston having a combustion chamber, which is composed of a main body and a mounting ring made of almost the same material.

Alternatively, according to the present invention, a piston body made of a metal material having a cavity centered on the central axis of the piston, a sub chamber having a nozzle insertion hole and a communication hole, which is disposed in the cavity via a heat shield air layer. A combustion chamber structure made of a heat-resistant high-temperature and high-strength material that is formed substantially in the center of the piston, and the combustion chamber structure disposed in the cavity by locking the combustion chamber structure in the cavity. The present invention relates to a structure of a piston having a combustion chamber, the mounting ring being made of substantially the same material as the piston body, which is joined at a joint part to the piston body for fixing.

In the structure of the piston having the combustion chamber, a member for controlling the amount of thermal expansion is provided between the upper surface of the convex portion provided on the outer periphery of the lower portion of the combustion chamber structure and the lower end surface of the mounting ring. Intervened. Further, a low thermal conductivity member is interposed between the thermal expansion amount control member and the upper surface of the convex portion of the combustion chamber structure and between the lower surface of the convex portion and the cavity wall surface of the piston body. . Alternatively, a low heat conduction member is provided between the upper surface of the convex portion provided on the outer periphery of the lower portion of the combustion chamber structure and the lower end surface of the mounting ring, and between the lower surface of the convex portion and the cavity wall surface of the piston body. Intervened.

Further, in the structure of the piston having the combustion chamber, a gap is formed between the inner peripheral surface of the mounting ring and the outer peripheral surface of the combustion chamber structure. Further, the upper outer peripheral surface of the mounting ring and the cavity wall surface of the piston body are welded, and a gap is formed between the lower outer peripheral surface of the mounting ring and the cavity wall surface of the piston body. Further, a sealing gasket is interposed between the undercut portion formed on the inner peripheral surface of the attachment ring and the step portion formed on the outer peripheral surface of the combustion chamber structure.

Further, in the structure of the piston having the combustion chamber, a cooling passage communicating with the lower portion of the piston body is formed between the outer peripheral surface of the mounting ring and the cavity wall surface of the piston body, and the cooling passage is formed. Boundary surfaces between the outer peripheral surfaces of the attachment ring above and below the passage and the cavity wall surface of the piston body are joined. The mounting ring forms the entire top of the piston, and the lower surface of the mounting ring is joined to the upper surface of the piston body.

[0014]

The structure of the piston having the combustion chamber according to the present invention is constructed as described above and operates as follows. That is, the structure of the piston having this combustion chamber, the combustion chamber structure made of heat resistant high temperature high strength material is arranged in the cavity formed in the piston body made of metal material via the heat shield air layer,
Since the combustion chamber structure is fixed in the cavity by a mounting ring that is arranged in the cavity on the outer periphery of the combustion chamber structure and is joined to the piston body and is made of substantially the same material as the piston body, Of the combustion chamber formed in substantially the center of the combustion chamber structure can be improved, the mounting ring absorbs the difference in thermal expansion between the combustion chamber structure and the piston main body, and the combustion chamber structure is fixed to the cavity wall surface of the piston main body. Press against to prevent backlash.
In particular, when the thermal expansion amount control member is interposed between the upper surface of the convex portion provided on the lower outer periphery of the combustion chamber structure and the lower end surface of the attachment ring, the thermal expansion amount control member Can adjust the amount of thermal expansion between the combustion chamber structure, the piston body, and the mounting ring to make the mounting structure between the members extremely robust.

Further, since the convex portion is formed in the lower temperature region of the combustion chamber structure, the change in temperature of the convex portion is small, the change in the amount of thermal expansion is small, and the combustion chamber structure is small. Is stably fixed without any play in the cavity of the piston body. Furthermore, a piston cooling passage can be easily formed in the piston body,
The combustion chamber can be kept at a high temperature, and the piston body can be kept at a low temperature.

Further, in the structure of the piston having the combustion chamber, since the heat-shielding air layer exists at the boundary surface between the combustion chamber structure and the piston body, heat dissipation from the combustion chamber to the piston body is caused. Can be prevented and the thermal efficiency can be improved. Further, since the combustion chamber is located substantially in the center of the piston, the reach distance of the jet flow from the communication hole is short, the combustion time is shortened, the performance is improved, and the reach distance of the jet flow from the combustion chamber is short. Therefore, the passage area of the communication hole can be formed large, the throttle loss can be reduced, and the efficiency can be improved.

[0017]

Embodiments of the structure of a piston having a combustion chamber according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the structure of a piston having a combustion chamber according to the present invention, and FIG. 2 is a top view of the piston in the structure of the piston having a combustion chamber of FIG.

Although not shown, the sub-chamber type engine incorporating the structure of the piston having the combustion chamber is, for example, a cylinder block forming a cylinder made of a metal material such as cast iron or aluminum alloy, and a gasket for the cylinder block. It has a cylinder head made of a metal material such as an aluminum alloy, which is fixed by interposing. The cylinder block may be formed by forming holes corresponding to the number of cylinders of the engine, and fitting a cylinder liner forming a cylinder into the holes. The cylinder head has intake and exhaust ports corresponding to the number of cylinders of the engine, that is, corresponding to the cylinders.
An intake / exhaust valve is arranged in the intake / exhaust port. A piston is incorporated in a cylinder formed in the cylinder block so as to reciprocate. The main chamber 20 is formed on the cylinder side between the lower surface of the cylinder head and the piston top surface 17, and in FIG. 1, is formed by the recessed portion of the piston top surface 17 formed by the tapered surface 18 of the piston top surface 17. ing.

This sub-chamber engine is a diesel engine that injects liquid fuel into the sub-chamber 2 from a fuel injection nozzle and burns it, and is characterized by the structure of a piston that reciprocates in a cylinder. The structure of the piston having the combustion chamber is such that the piston body 1 composed of the piston head portion 5 and the piston skirt portion 4 and the cavity 8 formed in the piston body 1 are arranged via the heat shield air layers 12 and 15. The combustion chamber structure 3 and the mounting ring 6 made of the same material as the piston body 1 for fixing the combustion chamber structure 3 to the piston body 1.

The structure of the piston having the combustion chamber is, in particular, a piston body 1 made of a metal material having a cavity 8 formed around the center axis of the piston, the cavity 8 being disposed in the cavity 8 via a heat shield air layer 12, and A combustion chamber structure 3 made of a heat-resistant high-temperature and high-strength material that constitutes a sub-chamber 2 having a nozzle insertion hole 9 and a communication hole 10 formed around the nozzle insertion hole 9 so as to be spaced apart from each other, at approximately the center of the piston. Also, in order to fix the combustion chamber structure 3 in the cavity 8, a mounting ring 6 made of substantially the same material as the piston body 1 which is arranged in the cavity 8 at the outer periphery of the combustion chamber structure 3 and is joined to the piston body 3. It consists of The mounting ring 6
Although it is not limited to the high thermal expansion material, it is basically preferable that the attachment ring 6 is made of the same material as the piston body 1 in consideration of welding or the like.
If a brazing filler metal or the like is used to fix the attachment ring 6 to the piston body 1 by welding or the like, the attachment ring 6 does not necessarily need to be made of the same material as the piston body 1, and therefore the attachment ring 6 is made of a material of substantially the same material as the piston body 1. It is made in.

Further, between the upper surface of the convex portion 13 provided at the lower portion of the outer periphery of the combustion chamber structure 3 and the lower end surface of the mounting ring 6, for controlling the amount of thermal expansion of a high linear expansion material, that is, a high thermal expansion material or the like. The member 7 is interposed. The fuel injection nozzle provided in the cylinder head is inserted into the nozzle insertion hole 9 near the center of the piston, and the wall surface is formed by the guide cylinder 16 depending on the length of the guide cylinder 16. The rushing period of the fuel injection nozzle into the sub chamber 2 is adjusted. Thermal expansion adjusting member, that is, thermal expansion amount controlling member 7
The required expansion coefficient of is determined by the coefficient of thermal expansion of the combustion chamber structure 3, which constitutes the combustion chamber, that is, the sub chamber 2. When the combustion chamber structure 3 is made of Si ₃ N ₄ and when made of a heat-resistant metal such as Incoloy 903, the coefficient of thermal expansion is significantly different. Will also be different.

For example, when the combustion chamber structure 3 is made of Si ₃ N ₄ , the material for the thermal expansion control member 7 needs to be made of a material having a large thermal expansion coefficient. When the structure 3 is made of a material other than Si ₃ N ₄ , the thermal expansion amount control member 7 is made of a different material. For example, in the thermal expansion amount control member 7, the combustion chamber structure 3 is made of Si ₃ N ₄
In the case of being manufactured by (1), it is manufactured from a material having a large thermal expansion coefficient such as a magnesium alloy. Also, the combustion chamber structure 3
When is made of a refractory metal, it is made of a material having a relatively large thermal expansion coefficient such as an Al alloy or a SUS material.

For example, the piston body 1 is made of Al alloy (A
C8A, made from LO-EX) or the like of metal, in which case the thermal expansion coefficient of 20-21 × 10 ^- is a ⁶ / ° C..
Further, the combustion chamber structure 3 is made of the same material as the piston body 1 that can be beam-welded or laser-welded to the piston body 1,
It is made of a metal such as Al alloy (A5052), in which case the coefficient of thermal expansion is 23 × 10 ⁻⁶ / ° C. The combustion chamber structure 3 is made of heat-resistant metal such as incoloy or Si ₃
N ₄ or the like are made from heat-resistant high-temperature high-strength material of the heat-resistant ceramics, when produced in Si ₃ N _4, the thermal expansion coefficient of 3.2 × 10 ^- is a ⁶ / ° C.. Further, the thermal expansion amount control member 7 is made of a magnesium alloy, and in this case, the thermal expansion coefficient is 26 × 10 ⁻⁶ / ° C.

In the structure of the piston having the combustion chamber, the inner peripheral surface of the mounting ring 6 and the upper outer peripheral surface 19 of the combustion chamber structure 3 are
A gap 30 is formed between and. Further, the upper outer peripheral surface of the mounting ring 6 and the cavity wall surface of the piston body 3 are joints 11 in which a part of the boundary surface is welded by beam welding or laser welding, and the lower outer peripheral surface of the mounting ring 6 and the piston body 3 are joined. A heat shield air layer 15 formed of a gap is formed between the wall surface of the cavity 3 and the cavity wall surface. In other words, the upper part of the mounting ring 6 on the top surface side of the piston is welded to the piston body 1, and the lower part of the mounting ring 6 forms a gap, that is, a heat-shielding air layer 15, with the piston body 1. Further, on the inner peripheral surface of the upper portion of the mounting ring 6, a locking portion 29 directed inward is provided.
Is provided, and the lower surface of the locking portion 29, that is, the undercut portion 22
Is a step portion 21 formed on the outer peripheral surface of the upper portion of the sub-chamber structure 3.
It is locked with a sealing gasket 14 interposed therebetween.
That is, between the undercut portion 22 formed on the inner peripheral surface of the attachment ring 6 and the step portion 21 formed on the outer peripheral surface 19 of the combustion chamber structure 3, the sealing gasket 14 made of an elastic member is provided. A heat shield air layer 15 that is a closed space is formed between the inner peripheral surface of the attachment ring 6 and the outer peripheral surface 19 of the combustion chamber structure 3 that is interposed. With the structure of the piston having the combustion chamber, the gap 30 between the mounting ring 6 and the combustion chamber structure 3 can allow a difference in thermal expansion between the piston body 1 and the combustion chamber structure 3 due to the above-mentioned configuration. The difference in thermal expansion is elastically absorbed by the gasket 14 for sealing.

In the combustion chamber structure 3, a sub-chamber 2 located substantially in the center of a cylinder or piston, a nozzle insertion hole 9 located in the center of the sub-chamber 2, and a circumferentially-spaced space around the nozzle insertion hole 9. A plurality of (6 in FIG. 2) communication holes 10 are formed. The communication hole 10 is formed in a circumferential direction around the nozzle insertion hole 9 in an inclined direction toward the cylinder peripheral side. Although not shown, the cylinder head is
A fuel injection nozzle having multiple injection holes arranged in the center of the cylinder shaft is fixed, and the injection hole portion of the fuel injection nozzle projects from the lower surface of the cylinder head. Therefore, in the nozzle insertion hole 9, multiple injection holes of the fuel injection nozzle arranged in the cylinder head are projected near the top dead center of the piston, and the fuel is sprayed from the multiple injection holes into the sub chamber 2. ing. In addition,
Although not shown, the cylinder head is provided with a glow plug for starting assistance, and the piston head 5
It is possible to form a plug hole in the hollow space and to allow the glow plug to project into the sub chamber 2 near the top dead center.

In the structure of the piston having the combustion chamber, a large number of communication holes 10 are formed around the nozzle insertion hole 9, and the passage areas of the communication holes 10 are dispersed over the entire circumference to be formed large as a whole. The flame and the air-fuel mixture ejected from the main chamber 2
It can mix well with the air in zero. That is, the communication hole 10 that connects the main chamber 20 and the sub chamber 2 can be configured to have a large passage area in total, and the throttle loss can be reduced and the output cannot be reduced. Further, since the sub chamber 2 is arranged concentrically on the cylinder center axis and the communication hole 10 is formed on the outer peripheral side surface of the sub chamber 2, the jet flow ejected from the sub chamber 2 has a large passage area of the communication hole 10. Even if the jetting energy becomes small and the reaching distance becomes short, the jet flow is generated in the main chamber 2
Can be mixed with the air present at 0 for a sufficiently short time,
It is possible to shorten the combustion period in the main chamber 20 and suppress the generation of HC and smoke.

FIG. 3 shows another embodiment of the structure of the piston having the combustion chamber. This example is different from the above examples except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same reference numerals are given to the same parts, and duplicate explanations are omitted. In this embodiment, the low thermal conductive member 24 is interposed between the thermal expansion amount control member 7 and the upper surface of the convex portion 13 of the combustion chamber structure 3, and the lower surface of the convex portion 13 and the piston body are also provided. The low heat conductive member 23
Is intervening. The low heat conductive members 23 and 24 are made of a material such as partially stabilized zirconia PSZ.

FIGS. 4 and 5 show another embodiment of the structure of the piston having the combustion chamber. Compared with the above-mentioned embodiment, this embodiment has the same configuration and the same function except that the low heat conductive member is interposed, and therefore, the same parts are designated by the same reference numerals, and duplicate description will be omitted. To do. In this embodiment, cooling passages 26, 27 communicating with the lower side of the piston body 1 are formed between the outer peripheral surface of the mounting ring 6 and the cavity wall surface of the piston body 1, and the cooling passages 26, 27 are mounted above and below. The boundary surface between the outer peripheral surface of the ring 6 and the cavity wall surface of the piston body 1 is joined, and the cooling passage 26 is hermetically sealed with respect to the tapered surface 18 of the piston top surface 17, and the piston is passed through the cooling passage 27. It is opened below the main body 1. Therefore, the oil from the crank chamber or the like passes through the cooling passage 27 and the cooling passage 26.
The piston body 1 on the outer periphery of the combustion chamber structure 3 is cooled and kept at a low temperature, and the sub chamber 2 formed in the combustion chamber structure 3 has a high temperature due to the presence of the heat shield air layer 15. Held in. Further, in this embodiment, the high thermal expansion member and the low thermal conductive member are not interposed between the mounting ring 6 and the convex portion 13 of the combustion chamber structure 3, but the mounting ring 6 is almost the same type as the piston body 1. The function of the high thermal expansion member can be sufficiently covered by making the material of the material and cooling the outer peripheral surface of the mounting ring 6 by flowing oil through the cooling passages 26 and 27.

FIG. 6 shows another embodiment of the structure of the piston having the combustion chamber. This example is different from the above examples except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same reference numerals are given to the same parts, and duplicate explanations are omitted. In this embodiment, the convex portion 13 provided on the outer periphery of the combustion chamber structure 3 is provided.
The low heat conductive member 24 is interposed between the upper surface of the base plate and the lower end surface of the mounting ring 6, and the low heat conductive member 23 is interposed between the lower surface of the convex portion 13 and the cavity wall surface 25 of the piston body 1. There is.

7 and 8 show another embodiment of the structure of the piston having the combustion chamber. Compared with the above-mentioned embodiment, this embodiment has the same configuration and the same function except that the low heat conductive member is interposed, and therefore, the same parts are designated by the same reference numerals, and duplicate description will be omitted. To do. In this embodiment, the mounting ring 6 has a piston top portion 28 extending to the periphery of the piston, and the lower surface of the mounting ring 6 and the upper surface of the piston body 1 are joined.

FIG. 9 shows another embodiment of the structure of the piston having the combustion chamber. This example is different from the above examples except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same reference numerals are given to the same parts, and duplicate explanations are omitted. In this embodiment, the convex portion 13 provided on the outer periphery of the combustion chamber structure 3 is provided.
A low heat conductive member 24 is interposed between the upper surface of the base plate and the lower end surface of the mounting ring 6, and a low heat conductive member 23 is interposed between the lower surface of the convex portion 13 and the cavity wall surface of the piston body 1. .

FIG. 10 shows still another embodiment of the structure of the piston having the combustion chamber. This example is
Compared with the above-mentioned respective embodiments, in each of the above-mentioned embodiments, a combustion chamber structure forming a sub chamber is arranged in the cavity of the piston body, whereas a main chamber, that is, a combustion chamber is formed in the cavity of the piston body. Except that the combustion chamber structure is arranged, the components have the same configuration and the same function, and therefore, the same components are designated by the same reference numerals, and duplicate description will be omitted. In this embodiment, the main chamber 20 is provided in the combustion chamber structure 3A.
That is, it relates to the structure of the piston forming the combustion chamber 2A. In this embodiment, the structure in which the combustion chamber structure 3A is fixed to the cavity 8 of the piston body 1 by using the mounting ring 6 is particularly useful for the combustion chamber structure 3 of the embodiment shown in FIG. Since they have the same structure and have the same function and function and effect as compared with those fixed by using the mounting ring 6, the description thereof will be omitted here.

Further, the structure of the piston having the combustion chamber according to the present invention is that of the embodiment shown in FIGS. 3, 4, 6, 7, and 9 in which the shape of the combustion chamber of the embodiment shown in FIG. 10 is shown. Can be applied to each. Although not shown, those examples correspond to those in which a combustion chamber as a main chamber is formed in the combustion chamber structure 3 shown in FIGS. 3, 4, 6, 7, and 9. The structure for attaching the combustion chamber structure to the piston body in these examples is the same as the structure shown in each of the above-mentioned drawings, and a description thereof will be omitted here. In each of the above embodiments, the combustion chamber is connected to the piston body 1
Although it is not shown in the figure in terms of the structure in which the combustion chamber structure that forms the combustion chamber is fixed to the piston body, the combustion chamber is offset from the piston center axis of the piston body. It may be formed at a different place, and the structure of the combustion chamber has a pointed opening,
The structure may be provided with a throat and is not limited.

[0034]

The structure of the piston having the combustion chamber according to the present invention is constructed as described above and has the following effects. The structure of the piston having the combustion chamber is such that the combustion chamber structure that constitutes the combustion chamber is arranged in the cavity formed in the piston body made of a metal material through the heat shield air layer, and the material is almost the same as the piston body. Since the outer periphery of the mounting ring made of is welded to the piston body to fix the combustion chamber structure in the cavity, the mounting ring is formed even if a difference in thermal expansion between the piston body and the combustion chamber structure occurs. The difference in thermal expansion between the two is adjusted by the thermal expansion of to firmly and satisfactorily fix it without any looseness. Further, since the heat-shielding air layer is formed between the piston body and the combustion chamber structure, the heat capacity of the combustion chamber structure can be reduced, the followability to the gas temperature can be improved, and the combustion can be performed. The heat shield effect of the chamber can be greatly improved, the heat energy released from the combustion chamber can be suppressed, and the fuel consumption can be improved.

In the structure of the piston having the combustion chamber, the difference in thermal expansion between the piston body and the combustion chamber structure can be adjusted by the mounting ring and the thermal expansion control member, so that the rattling is always stable. Therefore, the combustion chamber structure can be made of ceramics such as Si ₃ N _{4 having} a small coefficient of thermal expansion, and can have a structure with high heat resistance, so that a strong combustion chamber can be formed. Further, since the convex portion formed in the lower portion of the combustion chamber structure is fixed in the pressed state by the attachment ring, the lower portion of the combustion chamber structure has a small temperature change,
Since the change in the amount of thermal expansion is also small, the state of attachment of the combustion chamber structure to the piston body is always stable and a strong fixation can be secured.

Further, since a cooling passage for cooling can be easily formed in the piston main body, if the cooling passage is provided on the outer periphery of the combustion chamber structure and cooling oil is flown into the cooling passage, the combustion chamber structure is formed. The combustion chamber formed in the body can be kept at a high temperature, and the piston body can be kept at a low temperature. Further, if the heat shield air layer between the combustion chamber structure and the piston body is formed in a closed space by a sealing gasket, the heat shield degree of the combustion chamber can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of a piston having a combustion chamber according to the present invention.

2 is a top view of the piston of FIG. 1. FIG.

FIG. 3 is a sectional view showing another embodiment of the structure of the piston having the combustion chamber according to the present invention.

FIG. 4 is a sectional view showing still another embodiment of the structure of the piston having the combustion chamber according to the present invention.

5 is a top view of the piston of FIG.

FIG. 6 is a sectional view showing another embodiment of the structure of the piston having the combustion chamber according to the present invention.

FIG. 7 is a sectional view showing still another embodiment of the structure of the piston having the combustion chamber according to the present invention.

FIG. 8 is a top view of the piston of FIG.

FIG. 9 is a sectional view showing another embodiment of the structure of the piston having the combustion chamber according to the present invention.

FIG. 10 is a sectional view showing still another embodiment of the structure of the piston having the combustion chamber according to the present invention.

[Explanation of symbols]

 1 Piston main body 2 Sub-chamber 2A Combustion chamber 3 Combustion chamber structure 4 Piston skirt part 5 Piston head part 6 Mounting ring 7 Thermal expansion amount control member 8 Cavity 9 Nozzle insertion hole 10 Communication hole 11 Joint part 12,15 Heat shield air Layer 13 Outer peripheral convex portion 14 Gasket 19 Outer peripheral surface 20 Main chamber 21 Step portion 22 Undercut portion 23, 24 Low heat conductive member 25 Cavity wall surface 26, 27 Cooling passage 30 Gap

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02F 3/00 301 B 3/26 A

Claims (10)

[Claims] 1. A piston body made of a metal material having a cavity formed in the piston, and a combustion chamber structure made of a heat-resistant high-temperature high-strength material forming a combustion chamber arranged in the cavity through a heat-shielding air layer in the piston. And a piston body in which a part of the outer periphery is joined to the piston body by a joining portion for locking the combustion chamber structure inside the cavity by locking the combustion chamber structure inside the cavity. The structure of the piston with the combustion chamber is characterized in that it is composed of a mounting ring made of almost the same material as. 2. A piston main body made of a metal material having a cavity centered on the center axis of the piston, a sub-chamber arranged in the cavity with a heat shield air layer and having a nozzle insertion hole and a communication hole. A combustion chamber structure made of a heat-resistant high-temperature high-strength material that is formed in the center, and the combustion chamber structure that is locked in the outer periphery of the combustion chamber structure disposed in the cavity to fix the combustion chamber structure in the cavity. A structure of a piston having a combustion chamber, comprising: a mounting ring made of substantially the same material as the piston main body, a part of the outer periphery of which is bonded to the piston main body at a joint. 3. A thermal expansion amount control member is interposed between an upper surface of a protrusion provided on the outer periphery of the lower portion of the combustion chamber structure and a lower end surface of the mounting ring. A structure of a piston having a combustion chamber according to Item 1 or 2. 4. A low thermal conductivity member is interposed between the thermal expansion amount control member and the upper surface of the convex portion of the combustion chamber structure, and between the lower surface of the convex portion and the cavity wall surface of the piston body. The structure of a piston having a combustion chamber according to claim 3, wherein the piston has a combustion chamber. 5. Low heat between the upper surface of the convex portion provided on the outer periphery of the lower portion of the combustion chamber structure and the lower end surface of the mounting ring, and between the lower surface of the convex portion and the cavity wall surface of the piston body. The structure of a piston having a combustion chamber according to claim 1, wherein a conductive member is interposed. 6. The combustion chamber according to claim 1, wherein a gap is formed between an inner peripheral surface of the attachment ring and an outer peripheral surface of the combustion chamber structure. Structure of the piston with. 7. The upper outer peripheral surface of the mounting ring and the cavity wall surface of the piston body are welded together, and a gap is formed between the lower outer peripheral surface of the mounting ring and the cavity wall surface of the piston body. The structure of a piston having a combustion chamber according to any one of claims 1 to 6. 8. A gasket for sealing is interposed between an undercut portion formed on the inner peripheral surface of the attachment ring and a step portion formed on the outer peripheral surface of the combustion chamber structure. A structure of a piston having a combustion chamber according to any one of claims 1 to 7. 9. A cooling passage that communicates with a lower portion of the piston body is formed between an outer peripheral surface of the mounting ring and a cavity wall surface of the piston body, and the outer periphery of the mounting ring above and below the cooling passage is formed. The structure of a piston having a combustion chamber according to any one of claims 1 to 8, wherein a boundary surface between the surface and the cavity wall surface of the piston body is joined. 10. The mounting ring forms the entire top of the piston, and the lower surface of the mounting ring and the upper surface of the piston body are joined to each other.
The structure of the piston having the combustion chamber according to any one of 1.