JP3339198B2 - Piston structure with combustion chamber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, regarding a piston, an outer periphery of a ceramic crown having a cavity is fitted inside a head portion of a cylindrical aluminum skirt, and a plastic fluid material is interposed in a gap between the outer periphery of the ceramic crown and the head portion. A piston in which a plastic crown is joined to a ceramic crown and an aluminum skirt by deforming the material by heating and pressing is known.
A cast iron ring coexists with a plastic flowing material in the gap between the outer periphery of the combustion chamber and the head (see Japanese Utility Model Application Laid-Open No. 62-93141).
Reference).

[0003] Further, Japanese Patent Application No. Hei 5
No. 46175 discloses a sub-chamber 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 A fuel injection nozzle for injecting fuel into the auxiliary combustion chamber, wherein the fuel injection nozzle is disposed in the cylinder head and can protrude into a central communication port formed in the piston head near the top dead center of the piston; A plurality is formed in the circumferential direction eccentric from the center of the sub-combustion chamber, and the inflow direction to the sub-combustion chamber with respect to the cylinder axis is formed obliquely in the circumferential direction in a direction opposite to the swirl flow of the main combustion chamber; The direction in which the sub-combustion chamber blows out to the main combustion chamber is formed so as to be in a forward flow direction with respect to the swirl flow 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.
In addition, when the combustion temperature is high, it is effective to use a sub-chamber engine as a type of engine structure in order to perform fuel-rich combustion. 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 when the engine is configured as a sub chamber combustion chamber, a communication hole communicating the sub chamber and the main chamber is required. It is necessary to enlarge the cross-sectional area of the passage.

[0005] Conventional vortex-chamber-type engines require NO if the direction of the vortex formed in the vortex chamber, the direction of spray from the injection nozzle, and the timing of fuel injection from the injection nozzle do not match.
There is a problem that the generation of _X , smoke and the like increases. Also, in the vortex chamber type engine, since the communication port that communicates between the sub chamber and the main chamber is small, throttling loss occurs due to the communication port,
This causes the engine output to decrease. In general, since the communication port that connects the main chamber and the sub chamber is provided on the outer periphery of the cylinder, the distance that the jet must reach increases, and the mixing with the air in the main chamber becomes insufficient. And may cause HC and smoke.

Therefore, in the sub-chamber engine, the sub-chamber is provided at the center of the cylinder, a plurality of communication holes are provided for communicating the main chamber and the sub-chamber on the cylinder side, and energy injected from the sub-chamber to the main chamber through the communication holes is provided. It is conceivable to increase the cross-sectional area of the entire communication hole and reduce the drawing loss due to the communication hole without reducing the diameter. However, if the sub chamber is formed substantially at the center of the cylinder of the cylinder head, there is a problem that the area where the intake and exhaust ports are formed becomes small.
In order to solve this problem, it is conceivable to configure a sub chamber in a piston in a sub chamber engine. When a sub-chamber is formed in the piston, heat radiation from the sub-chamber becomes a problem.

Further, regarding a structure of a piston having a combustion chamber, when a combustion chamber structure forming a combustion chamber is attached to a cavity formed in the piston body, when the piston body is made of an Al alloy or cast iron, It is preferable that the structure is made of heat-resistant, high-temperature, high-strength material. In this case, however, the heat energy from the combustion chamber is determined by how strongly the combustion chamber structure is formed in the piston body and the combustion chamber structure is formed. It was an issue how to fix it in a state that reduces the heat dissipation of the steel.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. The combustion chamber is formed on the piston side to make the cylinder head a simple structure, the intake and exhaust ports are formed large, and the intake and exhaust ports are formed respectively. It is possible to form multiple cavities, especially to form a cavity in the piston body,
A combustion chamber structure, in which a combustion chamber is formed through a heat shield air layer, is disposed in the cavity, and the combustion chamber structure is firmly secured to the piston body without any backlash by using substantially the same material as the piston body to absorb thermal expansion. It is an object of the present invention to provide a piston structure having a combustion chamber in which the combustion chamber structure is fixed to a structure having a low heat capacity and is easy to assemble while suppressing heat dissipation from the combustion chamber to the piston body.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a piston body made of a metal material having a cavity formed in a piston, and a heat-resistant high-temperature high-pressure chamber having a combustion chamber disposed in the cavity with a heat shield air layer interposed therebetween. A combustion chamber structure made of a strength material, and an upper outer peripheral surface attached to the piston body for locking the combustion chamber structure in the cavity by locking to an outer periphery of the combustion chamber structure disposed in the cavity. And a mounting ring made of substantially the same material as the piston body joined to the piston body.

[0010] The present invention also provides a piston body made of a metal material having a cavity formed around the center axis of the piston.
A combustion chamber structure made of a heat-resistant, high-temperature, high-strength material which is disposed in the cavity with a heat shield air layer therebetween and has a sub-chamber having a nozzle insertion hole and a communication hole substantially at the center of the piston, and is disposed in the cavity; A fixing ring made of substantially the same material as the piston body, in which only an upper outer peripheral surface is joined to the piston body to lock the combustion chamber structure in the cavity by being locked to the outer periphery of the combustion chamber structure.
And a piston structure having a combustion chamber.

In the structure of the piston having the combustion chamber, a high linear expansion material is interposed between an upper surface of a projection provided on a lower outer periphery of the combustion chamber structure and a lower end surface of the mounting ring. ing. Further, a low heat conductive member is interposed between the high linear expansion material and the upper surface of the protrusion of the combustion chamber structure, and between the lower surface of the protrusion and the cavity wall surface of the piston body.

Alternatively, low heat is generated between an upper surface of a convex portion provided on an outer periphery of a lower portion of the combustion chamber structure and a lower end surface of the mounting ring and between a lower surface of the convex portion and a cavity wall surface of the piston body. A conductive member is interposed.

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.

In the structure of the piston having the combustion chamber, an upper outer peripheral surface of the mounting ring is welded to a cavity wall surface of the piston main body, and a lower outer peripheral surface of the mounting ring and a cavity wall surface of the piston main body are formed. A gap is formed between them.

In the structure of the piston having the combustion chamber, between an undercut portion formed on the inner peripheral surface of the mounting ring and a step formed on the outer peripheral surface of the combustion chamber structure, A gasket for sealing is interposed.

In the structure of the piston having the combustion chamber, a cooling passage communicating below the piston body is formed between an outer peripheral surface of the mounting ring and a cavity wall surface of the piston body. Boundary surfaces between the outer peripheral surface of the mounting 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.

In the structure of the piston having the combustion chamber, as described above, the combustion chamber structure made of a heat-resistant, high-temperature, high-strength material is arranged in a cavity formed in a piston body made of a metal material via a heat-insulating air layer. The combustion chamber structure is disposed in the cavity by an attachment ring made of substantially the same material as the piston body, which is disposed in the cavity on the outer periphery of the combustion chamber structure and has only an upper outer peripheral surface joined to the piston body. , The heat shielding property of the combustion chamber formed substantially at the center of the piston can be improved, and the mounting ring absorbs the difference in thermal expansion between the combustion chamber structure and the piston main body to form the combustion chamber structure. It is pressed against the cavity wall surface of the piston body to prevent backlash. In particular, when a high linear expansion material is interposed between the upper surface of the projection provided on the outer periphery of the lower portion of the combustion chamber structure and the lower end surface of the mounting ring, the high linear expansion material is applied to the combustion chamber. The amount of thermal expansion between the structure, the piston body and the mounting ring can be adjusted to make the mounting structure between the members extremely robust.

Further, since the convex portion is formed in the lower region of the combustion chamber structure where the temperature is low, the change in temperature of the convex portion is small, and the change in the amount of thermal expansion is small. Are stably fixed without generating backlash in the cavity of the piston body. Further, a passage for cooling the piston can be easily formed in the piston body,
The combustion chamber can be maintained at a high temperature, and the piston body can be maintained 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 between the combustion chamber structure and the piston body, heat is dissipated from the combustion chamber to the piston body. Is prevented, and the thermal efficiency can be improved. Further, since the combustion chamber is located substantially at the center of the piston, the distance of the jet from the communication hole is short, the combustion time is short, and the performance is improved, so that the distance of the jet from the combustion chamber is short. Therefore, the passage area of the communication hole can be made large, and the drawing loss can be reduced and the efficiency can be improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment 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 a piston having a combustion chamber according to the present invention, and FIG. 2 is a top view of the piston in the piston having a combustion chamber shown in FIG.

Although not shown, a sub-chamber engine incorporating the structure of the piston having the combustion chamber is, for example, a cylinder block constituting a cylinder made of a metal material such as cast iron or aluminum alloy, and a gasket attached to the cylinder block. And has a cylinder head made of a metal material such as an aluminum alloy and fixed with interposition. 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 at 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. In FIG. 1, the main chamber 20 is formed by a concave 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 from a fuel injection nozzle into the sub-chamber 2 and burns it, and is characterized by the structure of a piston that reciprocates in a cylinder. The structure of a piston having this combustion chamber is arranged in a piston body 1 composed of a piston head 5 and a piston skirt 4, and in a cavity 8 formed in the piston body 1 via heat shielding air layers 12 and 15. And a 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, disposed on the piston main body 1 and the cavity 8 made of a metal material having the cavity 8 formed around the center axis of the piston via the heat shield air layer 12, and A combustion chamber structure 3 made of a heat-resistant, high-temperature, and high-strength material, in which a sub-chamber 2 having a nozzle insertion hole 9 and a communication hole 10 formed at a distance around the nozzle insertion hole 9 is formed substantially at the center of the piston. 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 disposed in the cavity 8 on the outer periphery of the combustion chamber structure 3 and joined to the piston body 3. It is composed of The mounting ring 6
Although not limited to the high thermal expansion material, it is basically preferable to be made of the same material as the piston body 1 in consideration of welding and the like.
When a brazing material or the like is used to fix the mounting ring 6 to the piston body 1, the mounting ring 6 does not necessarily need to be made of the same material as the piston body 1. It is manufactured by.

Further, between the upper surface of the convex portion 13 provided at the lower part of the outer periphery of the combustion chamber structure 3 and the lower end surface of the mounting ring 6, there is provided a high linear expansion material, that is, a high thermal expansion material for controlling the amount of thermal expansion. The member 7 is interposed. The nozzle insertion hole 9 is located substantially at the center of the piston, and a fuel injection nozzle provided in the cylinder head protrudes near the piston top dead center. The wall surface of the nozzle insertion hole 9 is formed by a guide cylinder 16. The period during which the fuel injection nozzle enters the sub chamber 2 is adjusted. The required expansion rate of the thermal expansion adjusting member made of the high linear expansion material, that is, the thermal expansion amount controlling member 7 is determined by the thermal expansion coefficient of the combustion chamber structure 3 constituting the combustion chamber, that is, the sub-chamber 2. When the combustion chamber structure 3 is made of Si ₃ N ₄ and 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 member 7 for controlling the amount of thermal expansion 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 controlling member 7 is made of a different material. For example, the thermal expansion control member 7 is such that the combustion chamber structure 3 is made of Si ₃ N ₄
When it is manufactured by using a material having a large coefficient of thermal expansion such as a magnesium alloy. In addition, the combustion chamber structure 3
Is made of a heat-resistant metal, it is made of a material having a relatively large coefficient of thermal expansion, such as an Al alloy or a SUS material.

For example, the piston body 1 is made of an 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 perform beam welding or laser welding on the piston body 1.
It is made of a metal such as an Al alloy (A5052), in which case the coefficient of thermal expansion is 23 × 10 ⁻⁶ / ° C. The combustion chamber structure 3 is made of a 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 control member 7 is made of a magnesium alloy, in which 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 formed.
Is formed between them. A part of the boundary between the upper outer peripheral surface of the mounting ring 6 and the cavity wall surface of the piston body 3 is a welded portion 11 welded by beam welding or laser welding. A heat shield air layer 15 composed of a gap is formed between the cavity wall 3 and the cavity wall. In other words, the upper part of the mounting ring 6 on the piston top surface side is welded to the piston main body 1, and the lower part of the mounting ring 6 forms a gap between the piston main body 1, that is, a heat shielding air layer 15. Further, an inward locking portion 29 is provided on the upper inner peripheral surface of the mounting ring 6.
The lower surface of the locking portion 29, that is, the undercut portion 22 is provided.
Is a step portion 21 formed on the upper outer peripheral surface of the sub-chamber structure 3.
Are locked with a sealing gasket 14 interposed therebetween.
That is, between the undercut portion 22 formed on the inner peripheral surface of the mounting 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 of a closed space is formed between the inner peripheral surface of the mounting ring 6 and the outer peripheral surface 19 of the combustion chamber structure 3. According to 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 configuration. The difference in thermal expansion is elastically absorbed by the gasket 14 for sealing.

The combustion chamber structure 3 has a sub-chamber 2 located substantially at the center of the cylinder or piston, a nozzle insertion hole 9 located at the center of the sub-chamber 2, and a circumferential separation around the nozzle insertion hole 9. A plurality of (six in FIG. 2) communication holes 10 are formed. The communication hole 10 is formed in a circumferential direction around the nozzle insertion hole 9 so as to be inclined toward the cylinder peripheral side. Although not shown, the cylinder head has
A fuel injection nozzle having a multi-injection hole disposed at the center of the cylinder shaft is fixed, and the injection hole portion of the fuel injection nozzle protrudes from the lower surface of the cylinder head. Therefore, the multi-injection hole of the fuel injection nozzle arranged in the cylinder head is inserted into the nozzle insertion hole 9 near the piston top dead center, and the fuel is sprayed into the sub chamber 2 from the multi-injection hole. ing. In addition,
Although not shown, a glow plug for starting assistance is arranged in the cylinder head, and a piston head 5 is provided.
A plug hole is formed in the sub chamber 2 so that the glow plug protrudes 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 area of the communication holes 10 is formed so as to be distributed over the entire circumference and large as a whole. The flame and air-fuel mixture erupted from the main chamber 2
It can be mixed well with the air in 0. That is, the communication hole 10 communicating the main chamber 20 and the sub-chamber 2 can be configured to have a large passage area in total, so that the throttle loss can be reduced and the output is not 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 spouted from the sub-chamber 2 increases the passage area of the communication hole 10. Even if the jet energy is reduced and the reach is shortened, the jet flows into the main chamber 2
Can be mixed with the air present at zero for a short period of time,
The combustion period in the main chamber 20 can be shortened to suppress the generation of HC and smoke.

FIG. 3 shows another embodiment of the structure of the piston having the combustion chamber. This embodiment is different from the above embodiment except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same parts are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, a low thermal conductive member 24 is interposed between the thermal expansion control member 7 and the upper surface of the projection 13 of the combustion chamber structure 3, and the lower surface of the projection 13 and the piston body 1 between the cavity wall 25 and the low thermal conductive member 23.
Is interposed. 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. This embodiment has the same configuration and the same function except that a low thermal conductive member is interposed, as compared with the above embodiment. Therefore, the same parts are denoted by the same reference numerals, and duplicate description is omitted. I do. In this embodiment, cooling passages 26 and 27 communicating below 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 and 27 are mounted vertically. The boundary 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 sealed against the tapered surface 18 of the piston top surface 17, and the cooling passage 27 passes through the cooling passage 27. It is open below the main body 1. Therefore, oil from the crank chamber or the like flows through the cooling passage 27 through 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 is heated to a high temperature by the presence of the heat shielding air layer 15. Is held. In this embodiment, a high thermal expansion member and a low thermal conductive member are not interposed between the mounting ring 6 and the projection 13 of the combustion chamber structure 3. However, the mounting ring 6 is substantially the same as the piston body 1. The function of the high thermal expansion member can be sufficiently covered by 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 embodiment is different from the above embodiment except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same parts are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, the protrusion 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 mounting ring 6 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 projection 13 and the cavity wall surface 25 of the piston body 1. I have.

FIGS. 7 and 8 show another embodiment of the structure of the piston having the combustion chamber. This embodiment has the same configuration and the same function except that a low thermal conductive member is interposed, as compared with the above embodiment. Therefore, the same parts are denoted by the same reference numerals, and duplicate description is omitted. I do. In this embodiment, the mounting ring 6 has a piston top 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 embodiment is different from the above embodiment except that a low heat conductive member is interposed.
Since they have the same configuration and the same function, the same parts are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, the protrusion 13 provided on the outer periphery of the combustion chamber structure 3 is provided.
A low heat conducting member 24 is interposed between the upper surface of the mounting ring 6 and the lower end surface of the mounting ring 6, and a low heat conducting member 23 is interposed between the lower surface of the projection 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 embodiment is
Compared with the above embodiments, each of the above embodiments has a combustion chamber structure forming a sub chamber 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 for the difference in the arrangement of the combustion chamber structure, they have the same configuration and the same function. Therefore, the same components are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, the main chamber 20 is provided in the combustion chamber structure 3A.
That is, the present invention 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 main body 1 using the mounting ring 6 is, in particular, the combustion chamber structure 3 of the embodiment shown in FIG. Since they have the same structure and have the same functions and functions and effects as those fixed by using the mounting ring 6, the description thereof is omitted here.

Further, the structure of the piston having the combustion chamber according to the present invention is different from that of the embodiment shown in FIGS. 3, 4, 6, 7 and 9 in the embodiment shown in FIG. Can also be applied to each. Although not shown, these embodiments 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 mounting structure of the combustion chamber structure to the piston main body in these embodiments is the same as the structure shown in each of the above 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 the structure formed at substantially the center of the piston has been described, the structure of the combustion chamber forming the combustion chamber is fixed to the piston main body. Although not shown, the combustion chamber is offset from the central axis of the piston of the piston main body. Where the shape of the combustion chamber has a pointed opening,
It may have a structure with a throat, and is not limited.

[0037]

The structure of the piston having the combustion chamber according to the present invention is constructed as described above, so that even if a difference in thermal expansion between the piston body and the combustion chamber structure occurs, the thermal expansion of the mounting ring causes the piston ring to expand. By adjusting the difference in thermal expansion between the two, it is firmly fixed without any backlash. Further, since a heat shield 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 ability to follow the gas temperature can be improved, and the heat shielding effect of the combustion chamber can be greatly improved, the heat radiation from the combustion chamber can be suppressed, and the fuel efficiency 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 high linear expansion material, so that there is no play at all times. Therefore, the combustion chamber structure can be made of a ceramic such as Si ₃ N _{4 having} a small coefficient of thermal expansion.
It can be configured with a structure with high heat resistance, and can form a strong combustion chamber. Further, since the protrusion formed at the lower portion of the combustion chamber structure is fixed in a pressed state by the mounting ring, the lower portion of the combustion chamber structure has a small temperature change and a small change in the amount of thermal expansion. Therefore, the state of attachment of the combustion chamber structure to the piston main 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 body, the cooling passage is provided on the outer periphery of the combustion chamber structure, and the cooling oil flows through the cooling passage. The combustion chamber formed in the body is kept at a high temperature, and the piston body can be kept at a low temperature. Furthermore, 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 of the combustion chamber can be increased.

[Brief description of the drawings]

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

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

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.

FIG. 5 is a top view of the piston of FIG. 4;

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. 7;

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]

 DESCRIPTION OF SYMBOLS 1 Piston main body 2 Subchamber 2A Combustion chamber 3 Combustion chamber structure 4 Piston skirt part 5 Piston head part 6 Mounting ring 7 Member for controlling thermal expansion (high linear expansion material) 8 Cavity 9 Nozzle insertion hole 10 Communication hole 11 Joint 12, 15 heat shield air layer 13 outer peripheral projection 14 gasket 19 outer peripheral surface 20 main chamber 21 step 22 undercut portion 23, 24 low heat conduction member 25 cavity wall surface 26, 27 cooling passage 30 gap

Continuation of the front page (56) References JP-A-7-269353 (JP, A) JP-A-5-10209 (JP, A) JP-A-7-19052 (JP, A) JP-A-6-241049 (JP) , A) Japanese Utility Model Showa 59-117861 (JP, U) Japanese Utility Model Showa 62-93141 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 1/00-23/10 F02F 3/00-3/28

Claims (10)

(57) [Claims] 1. A piston in the piston body made of a metallic material forming the cavity, the combustion chamber structure made of heat high-temperature high-strength material forming the combustion chambers arranged over the thermal barrier air layer to said cavity in said piston And the piston body having only an upper outer peripheral surface joined to the piston body to lock the combustion chamber structure inside the cavity by engaging with the outer periphery of the combustion chamber structure disposed in the cavity. mounting ring made of the same material, it is composed of
Structure of a piston having a combustion chamber, characterized in that there. 2. A piston main body made of a metal material having a cavity formed around a piston central axis, and a sub-chamber disposed in the cavity with a heat shield air layer and having a nozzle insertion hole and a communication hole is provided substantially with a piston. A combustion chamber structure made of a heat-resistant, high-temperature, high-strength material formed in the center, and the combustion chamber structure disposed in the cavity and fixed to the outer periphery of the combustion chamber structure to fix the combustion chamber structure in the cavity. mounting ring of the piston body and the piston body only upper outer peripheral surface are bonded consisting substantially the same material, consists
Structure of a piston having a combustion chamber, characterized in that that. 3. A high line between the lower end surface of the upper surface and the mounting ring of the protrusion provided on the lower periphery of said combustion chamber structure
The structure of a piston having a combustion chamber according to claim 1 or 2, wherein an expansion material is interposed. 4. A low heat conduction member is interposed between the high linear expansion material and an upper surface of the protrusion of the combustion chamber structure, and between a lower surface of the protrusion and a cavity wall surface of the piston body. The structure of a piston having a combustion chamber according to claim 3, wherein the piston is provided. 5. Low heat is generated between an upper surface of a projection provided on an outer periphery of a lower portion of the combustion chamber structure and a lower end surface of the mounting ring and between a lower surface of the projection and a cavity wall surface of the piston body. The structure of a piston having a combustion chamber according to any one of claims 1 to 4, 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 mounting ring and an outer peripheral surface of the combustion chamber structure. Piston structure with. 7. An upper outer peripheral surface of the mounting ring is welded to a cavity wall surface of the piston body, and a gap is formed between a lower outer peripheral surface of the mounting ring and a 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 an inner peripheral surface of the mounting ring and a step formed on an outer peripheral surface of the combustion chamber structure. The structure of a piston having a combustion chamber according to any one of claims 1 to 7. 9. A cooling passage communicating below 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 piston according to claim 1, wherein the mounting ring forms the entire top of the piston, and a lower surface of the mounting ring is joined to an upper surface of the piston body.
The structure of the piston having the combustion chamber according to any one of the above.