JPS6093161A - Heat-insulated piston structure - Google Patents

Abstract

PURPOSE:To facilitate the coupling between a ceramic crown and a piston body, by fitting a projection formed on the crown into a receiving hole in the top end part of the piston body, and by heating and pressing the surrounding area around the receiving hole. CONSTITUTION:A piston body 2 made of aluminum or forgeable cast iron, is formed by cutting in its outer surface with ring grooves 10 through 12, and is also formed in its top end part with a receiving hole 15. A crown 1 made of ceramics such as, for example, silicon nitride is formed in the peripheral edge part of its lower end face with a projection 19 which is superposed on the top edge part of the piston body 2 through the intermediary of a ring 4, is also defined in its center section with a combustion chamber 9 and is integrally incorporated with a projection 5 downardly extending. Further, the inner end wall 2a of the piston body 2 is heated and pressed in the part adjacent to the projection 5 in dies 6 so that the projection 5 is fitted into the receiving hole 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an adiabatic piston used in an adiabatic engine.

By using ceramics in the wall surrounding the combustion chamber of the engine, the combustion gas is prevented from dissipating to the outside, and the exhaust gas is exhausted under high temperature conditions. An adiabatic engine has already been proposed in which the engine is fed to a device, thereby increasing the output and improving the thermal efficiency of the engine.

In the piston of an adiabatic engine, a piston body made of aluminum or the like and a crown made of ceramic are generally fastened together using heat-resistant bolts or the like, or by the cylindrical method.

However, when fastening with POL~, loosening occurs due to aging cycles and fluctuations in combustion pressure, and cast-wrapped ones may break due to thermal stress, so they have not yet reached a level of practical use.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 57-2445, a piston using ceramics for the crown that partitions the combustion chamber has been proposed, but this requires a complicated connection structure with the piston body made of aluminum or the like. However, it takes a lot of effort and time to do so.

An object of the present invention is to provide a structure of an insulating piston that is simple in construction and assembly and suitable for industrial use.

For this reason, the configuration of the present invention is such that a fitting hole is provided at the upper end of the piston body, a protrusion formed on the crown is fitted into the fitting hole, and the area around the fitting hole of the piston body is heated and pressurized. The main body and the crown are joined together.

The present invention will be explained based on examples. J shown in Figure 1,
According to the present invention, a piston main body 2 including a piston eye socket J-1 and a crown 1 made of ceramics such as silicon nitride connected to one end of the piston main body 2 are joined in an inclined manner. be done. The piston body 2 is made of aluminum.
:I;1 It is constructed of I4 forged U iron, and links 10, 11, and 12 are cut into the outer peripheral surface. A fitting hole 15 is provided at the upper end, and a pin hole 13 into which a known piston pin is fitted is provided from the crotch 1 in the peripheral wall.

The crown 1σ is flat at one end and 11 is flat, and a protrusion 19 is attached to the periphery of the lower end of the two screws 142 and is overlapped with the edge of the ring 4 through the ring 4.
A protrusion 5 that defines a combustion chamber 9 and projects downward is integrally formed in the center. Then, this protrusion 5 is screwed into the fitting hole 1 of the main body 2, and a ceramic fiber or stainless steel mesh is inserted into the space between the protrusion 19 and the protrusion 5. The heat insulating material 3 is sandwiched.

The ring 4 is engaged with an annular groove formed at the E end of the piston body 2. The heat insulating materials 3 and 1 are formed by knitting or intertwining ceramic fibers or stainless steel wires.

In the present invention, in particular, the outer circumferential surface of the protrusion 5 is formed in advance to have a rough surface, and this is fitted into the fitting hole 15 of the screw body 2, and as shown in FIG. The portion of the inner end wall 2a of the inner end wall 2a approaching the protrusion 5 is heated and pressurized using a die 6, thereby bringing the fitting portion with the protrusion 5 into tight pressure contact. The die 6 is a cup-shaped die preferably made of ceramics that can withstand compressive loads, and is heated in advance by an appropriate means, and then the lower end 6a is inserted into the piston body 2. 2a to deform the upper wall of the piston body 2 and bring the fitting portion of the protrusion 5 into the fitting hole 15 into close contact. Even after heating, the die 6 is cooled while maintaining the pressurized state to prevent loosening due to subsequent thermal expansion.

Instead of having a cup shape, the die 6 is provided with a plurality of protrusions along the circumferential direction on the end portion 6a, whereby the fitting portion between the fitting hole 15 and the protrusion 5 is locally heated and deformed. You may also do so.

When connecting the crown 1 to the piston body 2.

The piston body 2 is heated in advance by high frequency heating means or the like to the softening point of the metal, MC = 400-500°C, 600°C for 1 alloy steel, and 300°C for aluminum.
After step A, pressure is applied using die 6.

In this way, the softened portion of the piston body 2 is crimped to the protrusion 5 of the crown 1 made of ceramics, and since it is cooled under pressure, the pressure detection saw remains and the connection with the protrusion Ni5 Power is strengthened.

As shown in Fig. 3, the fitting part between the screw body 2 and the protrusion 5 of the crown 1 is made of Kovar (F e-N 1-Co alloy) which has the same coefficient of thermal expansion as ceramics. An even tighter connection can be achieved by inserting a ring 1B made of an alloy such as can get.

In addition, in a T-bill engine in which fuel is injected directly toward the wall of the combustion chamber 9, a groove 225 is formed in the fitting hole 15 on the piston pin in the part that is in contact with the fuel, as shown in FIG. - It is preferable to provide a space between the protrusion 5 and the protrusion 5.

As mentioned above, the present invention differs from the conventional means using bolts or castings, in that the crown 1 made of ceramics is fitted into the piston body 2 made of aluminum or the like, and this fitting part is mechanically pressure-welded. Therefore, it is possible to eliminate conventional problems such as excessive tightening stress caused by over-tightening the bolt between the crown 1 and the piston body 2, and internal stress caused by high temperature melting during casting. Since the structure and assembly are simple, agricultural production is easy, and the heat insulating piston can be provided at low cost.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of the structure of the heat insulating piston according to the present invention, Figs. 2 and 3 are front sectional views showing the manufacturing process of the heat insulating piston, and Fig. 4 is a partially modified embodiment of the present invention. FIG. 3 is a plan sectional view of the structure of the heat insulating piston according to the invention. 6- 1: Tara S7n 2: Piston body 3: Insulating material 5: Protrusion 15: Fitting hole Patent applicant I'1 Toshio Jidosha Co., Ltd. Patent attorney 1111 Toshio Moto 71

Claims (1)

[Claims] A fitting hole is provided at the upper end of the piston body, a protrusion formed on the crown is fitted into the fitting hole, and the area around the fitting hole of the screw body is heated and pressurized to connect it to the screw body. The structure of a heat insulating screw characterized by joining the crown.