JP2903742B2 - Manufacturing method of 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 method of manufacturing a combustion chamber in which a ring-shaped lip is disposed in a cavity formed in a piston head body to form a combustion chamber opening.

[0002]

2. Description of the Related Art Conventionally, as a ceramic built-in type piston, there is one disclosed in Japanese Utility Model Laid-Open Publication No. 60-141446. The ceramic built-in type piston disclosed in the publication has a ceramic member incorporated in a recess on the combustion chamber side of a piston body made of an aluminum alloy, and has a coefficient of thermal expansion of 10 to 23 × 10 on the outer periphery of the ceramic member. ^-1 /
And a metal ring having a protrusion having a plurality of fastening holes at its head is joined so that the protruding end protrudes from the upper end surface of the ceramic member. And a male threaded portion screwed into a female threaded portion provided in the concave portion is formed into a threaded assembly, and this assembly is fastened to the piston body, and then a protrusion including the fastening hole is removed.

As a piston for an internal combustion engine, there is one disclosed in Japanese Utility Model Laid-Open No. 58-98455. The piston for an internal combustion engine is aluminum, the piston base made of a metal material such as cast iron, Kovar, 42 thermal expansion coefficient of such alloy is 3 to 9 × 10 ^- the union of ceramics through a ⁶ / ° C. of the metal body It is.

[0004]

When a reentrant combustion chamber is used as a combustion chamber formed in a piston head body in a combustion chamber of a direct injection diesel engine, the tip of a lip forming an opening of the combustion chamber is pointed. The turbulence of air flowing into and out of the cylinder and the combustion chamber, i.e., the turbulence of the squish flow and the reverse squish flow increases, the mixing of air and fuel is promoted, and the generation of the air-fuel mixture becomes faster, Combustion that can improve the combustion state and reduce the generation of smoke can be ensured.

However, in a conventional piston made of aluminum or ceramic fiber reinforced aluminum, if the tip of the lip constituting the combustion chamber is sharply formed, the temperature of the tip of the lip becomes high. In addition, the thermal load applied to the lip, that is, thermal stress, causes the lip to melt, cracks, and other damages, and there is a limit to sharpening the tip of the lip. When a non-aluminum material having excellent heat resistance such as niresist, steel, Fc, or ceramics is used at the tip of the lip portion, the coefficient of thermal expansion between the lip portion and the aluminum material constituting the piston head body is increased. And a large difference occurs, and peeling or the like occurs on the boundary surface or the bonding surface, which is problematic.

[0006] The above-mentioned problem is caused by the above-mentioned Japanese Utility Model Application Laid-open No.
The ceramic built-in piston disclosed in Japanese Patent No. 41446 has a similar problem. That is, the ceramic built-in type piston is a piston body made of an aluminum alloy, in which a metal ring is fastened with a screw and the metal ring is joined to a ceramic member, but the metal and the ceramic have different coefficients of thermal expansion. In a piston head that receives thermal stress, cracks and cracks occur in the ceramic member, and there is a problem of damage to the ceramic member.

Further, when the iron / nickel-based functionally graded metal combination and the aluminum piston head body are joined by metal flow, the difference in magnetic permeability causes the functionally graded metal combination to generate heat from the piston head body. High temperature, 800 ℃ -1100 required for metal flow
° C. However, in this case, the temperature of the piston head itself increases due to heat conduction from the functionally graded metal combination. For this reason, there is a problem that the piston head body is also deformed when the functionally graded metal joint is plastically deformed by metal flow, and the two cannot be joined by metal flow.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a combustion head formed in a metal piston head body having a top surface extending in a radially inwardly pointed ring shape and having an opening in the center. In a chamber, a lip portion made of a ceramic material having high temperature strength and heat resistance is joined to an inner wall surface of a ring joined body made of a functionally graded metal material having a different coefficient of thermal expansion to form a lip assembly. When the piston head body is joined to the outer peripheral surface of the piston head by metal flow, only the cavity wall surface of the piston head body is locally heated, whereby plastic deformation due to metal flow is locally generated in the piston head body, and the lip It is an object of the present invention to provide a method of manufacturing a combustion chamber that securely connects an assembly to a piston head body.

[0009]

The present invention is configured as follows to achieve the above object. That is,
The present invention provides a lip assembly in which a lip portion made of a heat-resistant and high-strength ceramic material forming a combustion chamber opening is connected to the inner wall surface of a functionally graded metal composite made of a functionally graded material having a different coefficient of thermal expansion. Manufacturing the lip assembly, arranging the outer peripheral surface of the lip assembly on the wall surface of the cavity formed in the metal piston head main body, and then locally heating only the cavity wall surface portion of the piston head main body to metallize the portion. Plastically deforming by flow and joining the lip assembly to the piston head body.

In the method for manufacturing a combustion chamber, a protrusion protruding from an upper surface of the piston head body is formed on a wall surface of the cavity adjacent to the lip assembly, and a pressing jig is brought into contact with the protrusion. Then, by heating the press jig by high frequency, only the protruding portion and the vicinity thereof are locally heated, and the protruding portion undergoes metal flow and undergoes plastic deformation.

[0011]

The method of manufacturing a combustion chamber according to the present invention is configured as described above, and operates as follows. That is, in this method of manufacturing the combustion chamber, the outer peripheral surface of the lip assembly is arranged on the wall surface of the cavity formed in the metal piston head body,
Since only the cavity wall portion of the piston head body is locally heated and the portion is plastically deformed by metal flow, the lip assembly can be securely joined to the piston head body.

In addition, a projection is formed on the cavity wall surface adjacent to the lip assembly so as to project from the upper surface of the piston head body, and a pressing jig is brought into contact with the projection to heat the press jig by high frequency. In addition, only the protruding portion and a portion near the protruding portion can be metal-flowed to be plastically deformed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of a method for manufacturing a combustion chamber according to the present invention will be described below. FIG. 1 is a schematic cross-sectional view showing one embodiment of a piston manufactured by the method of manufacturing a combustion chamber according to the present invention, FIG. 2 is a schematic explanatory view illustrating one embodiment of a method of manufacturing a combustion chamber according to the present invention, and FIG. FIG. 3 is a schematic explanatory view showing a state where a lip assembly is joined to a piston head body.

As shown in FIG. 1, a piston manufactured in one embodiment of a method of manufacturing a combustion chamber according to the present invention has a cavity 1 forming a combustion chamber 1 formed in a piston head body 2.
The present invention relates to an embodiment of a reentrant piston having a loop-shaped lip portion 8 extending in a radially inwardly tapered shape so as to cover an upper portion of the piston 0 and having a combustion chamber opening 3. This reentrant type piston comprises a piston head body 2 made of a metal material such as aluminum, aluminum alloy, cast iron or the like, having a piston skirt cast and formed and a cavity 10 fixed to the piston skirt and constituting a combustion chamber 1. Chamber 1 is cavity 1
0 has an opening 3 and a bottom surface 4 of a cavity 10 having a larger area than the opening 3. This piston is characterized by an upper wall structure constituting the combustion chamber 1, and is a ring-joined body made of a functionally graded metal material joined to a cavity wall surface 5 formed in a cavity 10 formed in the piston head main body 2. And a lip portion 8 which is joined to the ring assembly 6 and extends radially inward and sharply into a loop to form a combustion chamber opening 3 at the center.

In this reentrant piston,
The lip portion 8 is made of a material having high heat resistance and high temperature strength, for example, silicon nitride (Si ₃ N ₄ ), silicon carbide (Si).
C) and the like. The lip portion 8 has a shape in which the tip forming the combustion chamber opening 3 is formed to have a very sharp angled point, and has a tapered surface 11 that is inclined upward and downward inward in the radial direction with the outer circumferential surface as a boundary at the center. Has been produced.

As shown in FIG. 2, the ring assembly 6 is composed of a plurality of (four in the figure) rings 12, 13, 14, and 15 which are sequentially arranged in the radial direction and adjacent peripheral surfaces are joined to each other. The inner ring is made of a functionally graded metal material having a lower coefficient of thermal expansion than the outer ring. For example, the functionally graded metal material of the ring assembly 6 is
It is made of a metal material having a coefficient of thermal expansion intermediate between the coefficients of thermal expansion of the piston head 2 and the piston head body 2, for example, nickel-based, cobalt-based, and iron-based metal materials. Specifically, the innermost peripheral ring 12 is
The outermost ring 15 is made of Incoloy, and the outermost ring 15 is made of an alloy.
4 is made of a material having a thermal expansion coefficient intermediate between that of Kovar and Incoloy, and the rings 12, 13, 14, 15 are joined to each other by brazing or the like to form an integral structure. By manufacturing each ring with the above-mentioned material, the lip 8
The ring 12 located on the side can be made of a material having a coefficient of thermal expansion close to the coefficient of thermal expansion of the lip portion 8, and the ring 15 located on the side of the piston head body 2 has a coefficient of thermal expansion close to the coefficient of thermal expansion of the piston head body 2. Rate material. Therefore, the ring joined body 6 is configured so that the coefficient of thermal expansion changes stepwise from the inner peripheral side to the outer peripheral side, and the coefficient of thermal expansion close to that of a ceramic material such as silicon nitride, silicon carbide, or the like increases the aluminum or aluminum alloy. It is configured in a state close to the coefficient of thermal expansion of a metal material such as.

In the method of manufacturing a piston according to the present invention, as shown in FIG. 2, the ring assembly 6 includes a plurality of rings 12, 1 made of functionally graded metal materials having different coefficients of thermal expansion.
3, 14, 15 are sequentially arranged in the radial direction, and adjacent peripheral surfaces are joined to each other. Ring joint 6
Shape of the ring 1 outside the height of the inner ring 12
5 is formed such that the upper surface is horizontal and the lower surface is tapered as a whole so that the height of 5 is increased. In particular, the outer peripheral surface 16 of the ring assembly 6 is formed with tapered surfaces 23 and 24 whose upper and lower portions extend radially inward. It is preferable that the inner peripheral surface of the inner ring 12 is formed as a tapered surface 30 whose lower peripheral surface protrudes inward in the radial direction to form a receiving portion of the lip portion 8. After the ring assembly 6 is manufactured, the outer peripheral surface 18 of the lip 8 is joined to the inner wall surface 19 of the ring assembly 6 by a metal flow or the like to manufacture the lip assembly 20.

After the lip assembly 20 is manufactured, the outer wall surface 16 of the lip assembly 20 is arranged and set on the upper wall surface of the cavity 10 formed in the piston head main body 2.
In this case, the cavity wall 5 of the piston head body 2
The lower half has a tapered surface 22 extending inward in the radial direction, and the upper half has a cylindrical surface 31 extending straight. Further, on the wall surface forming the cavity 10 of the piston head main body 2, a protruding portion 7 protruding from the upper surface 17 of the piston head main body 2 is formed on the cavity wall surface portion adjacent to the lip assembly 20.

In addition, a contact portion 27 is formed on the lower surface of the piston head body 2 corresponding to the projecting portion 7 for applying a contact member 26 when the projecting portion 7 is pressed. Therefore, when the lip assembly 20 is arranged on the wall surface of the piston head main body 2, the tapered surface 24, which is the outer peripheral surface of the lip assembly 20, is supported by the tapered surface 22 of the piston head main body 2. In this state, a space 21 is formed between the upper wall surface of the piston head main body 2 and the outer peripheral surface of the upper part of the lip assembly 20 for metal to enter by a metal flow.

Next, the press jig 9 is brought into contact with the protruding portion 7, and the high-frequency coil 25 is arranged close to the press jig 9. The press jig 9 is made of S50C or the like, and by applying a current to the high-frequency coil 25, only the protrusion 7 of the piston head main body 2 is heated by high frequency through the press jig 9. For example, when the press jig 9 is heated to 700 ° C. to 800 ° C. by the high-frequency coil 25, the protrusion 7 is heated to 300 ° C. to 350 ° C. by heat conduction through the press jig 9 and reaches a sufficient temperature as a metal flow. Become. When only the protruding portion 7 and its vicinity are locally heated, the protruding portion 7 is pressed by the press jig 9, and the protruding portion 7 undergoes metal flow and is plastically deformed. Invading the space 21 between the tapered surface 23 which is the outer peripheral surface of the upper part of the assembly 20,
The piston head body 2 and the lip assembly 20 are joined. Moreover, since the metal material of the piston head main body 2 enters the space 21 and the lip assembly 6 is wrapped by the upper and lower walls of the piston head main body 2, the lip assembly 6 is mechanically firmly connected. .

The piston head body 2 and the lip assembly 20
Then, the abutting portion 27 formed on the cavity wall surface of the piston head body 2 is cut to finish it into a smooth surface.

Next, another embodiment of the method for manufacturing a combustion chamber according to the present invention will be described with reference to FIGS. FIG. 4 is a schematic explanatory view illustrating an embodiment of a method for manufacturing a combustion chamber according to the present invention, and FIG. 5 is a schematic explanatory view illustrating a state in which a lip assembly is joined to a piston head body. Since the method of manufacturing the combustion chamber according to this embodiment is completely the same as that described above except that the shape of the outer peripheral surface of the lip assembly 20 is different, the same parts are denoted by the same reference numerals. , Overlapping description will be omitted.

As shown in FIG. 4, the ring 15 of the ring assembly 6 forming the outer peripheral portion of the lip assembly 20 has a concave portion 28 formed on the outer peripheral surface so that an intermediate portion is radially inward. Therefore, when the lip assembly 20 is disposed on the wall surface of the piston head main body 2, a space 29 is formed between the upper wall surface of the piston head main body 2 and the outer peripheral surface in the middle of the lip assembly 20. Therefore, similarly to the above, when only the protruding portion 7 and the vicinity thereof are locally heated, the protruding portion 7 is pressed by the press jig 9, and the protruding portion 7 undergoes metal flow and is plastically deformed. Invading the part 29,
The piston head body 2 and the lip assembly 20 are joined. In addition, since the metal material of the piston head body 2 enters the space 29, the lip assembly 6 is mechanically and strongly connected to the piston head body 2.

Since the piston according to the present invention is configured as described above, it operates as follows. That is, even if a large thermal stress is generated due to a difference in thermal expansion between the lip portion 8 and the piston head body 2 due to a temperature difference when the engine is operated, the ring joint body 6 made of the functionally graded metal material serves as a cushioning material. It functions and absorbs a difference in thermal expansion between the lip portion 8 and the piston head body 2 due to a temperature difference. Therefore, even if a temperature change occurs in the combustion chamber 1 and a difference in thermal expansion occurs between the lip portion 8 and the piston head main body 2, no crack, crack, or the like occurs in the lip portion 8, and the combustion chamber 1 is maintained. There is no destruction. In addition, the lip portion 8 is pointed and has an acute angle, and heat inflow from the combustion gas is large.
The heat that has flowed into the lip 8 flows through the ring connector 6 in the direction of the piston head body 2 without being obstructed, and flows out to the cylinder liner side through the piston skirt, the piston ring, and the like. Therefore, the temperature of the lip portion 8 is suppressed from rising without maintaining the temperature of the lip portion 8 at a high temperature. Therefore, even if the edge of the lip portion 8 is formed in a sharp pointed shape, it is manufactured with heat resistance. Does not melt or break.

Since the lip portion 8 is made of a material such as ceramics having a low coefficient of thermal expansion and high heat resistance, the edge of the lip portion 8 forming the combustion chamber opening 3 is formed at an extremely acute angle and the shape thereof is increased. Can be maintained even at high temperatures. Therefore, it is possible to increase the squish flow generated in the compression stroke when the piston is raised and the reverse squish flow generated in the explosion stroke when the piston is lowered. Combustion for reducing consumption can be performed, and the combustion state can be improved.

[0026]

The method for manufacturing a combustion chamber according to the present invention has the following effects because it is configured as described above. That is, this method of manufacturing a combustion chamber includes a lip portion made of a heat-resistant high-strength ceramic material that forms a combustion chamber opening on the inner wall surface of a functionally graded metal combination made of a functionally graded material having a different coefficient of thermal expansion. Manufacturing the lip assembly by coupling, arranging the outer peripheral surface of the lip assembly on the wall surface of the cavity formed in the metal piston head body, and then locally heating only the cavity wall portion of the piston head body Then, the part is plastically deformed by metal flow,
Since the lip assembly is joined to the piston head main body, only the metal material of the piston head main body undergoes metal flow and plastic flows, and the lip assembly does not flow metal. Are securely and firmly joined.

Further, in this manufacturing method of the combustion chamber, a protruding portion protruding from the upper surface of the piston head body is formed on the cavity wall portion adjacent to the lip assembly, and the pressing jig is brought into contact with the protruding portion. When the press jig is heated by high frequency, only the protrusion is locally heated by heat conduction, and the protrusion and the vicinity thereof are subjected to metal flow and plastically deformed. The protruding portion and the portion in the vicinity thereof plastically flow into the space formed in the above, and are joined together and mechanically joined together.

Further, heat is satisfactorily conducted without obstructing heat flow at each boundary from the tip to the outer periphery of the piston head main body at the lip, and the heat at the tip of the lip is transferred to the outer periphery of the piston head and the piston. The lip can be moved to the outside through a ring, a cylinder liner, or the like to prevent the lip from becoming hot, thereby preventing the lip from being melted due to high temperature. The difference in expansion can be absorbed, and even if thermal stress is applied due to the temperature difference, cracking of the lip can be avoided. Therefore, even when the tip of the lip is sharply pointed, even if the tip of the lip becomes hot due to the combustion gas, the heat is immediately transferred to avoid maintaining the hot state. ,
Melting of the lip tip due to high temperature can be prevented.

Therefore, the lip portion is made of a material having a high heat resistance, so that the edge of the lip portion is prevented from being melted even if the lip portion is formed to be sharp at an acute angle, and the sharp-edged edge is formed. The shape can be maintained. Therefore, the lip portion can be formed at an acute angle and the edge of the lip portion can be formed at an acute angle, so that the squish flow flowing into the combustion chamber generated in the compression stroke of the ascent of the piston and the explosion stroke of the descent of the piston The reverse squish flow generated from the combustion chamber and flowing out of the combustion chamber can be increased, and the squish flow and the mixing of the atomized fuel and the air by the reverse squish flow can be more favorably achieved, as compared with the conventional reentrant piston. In addition, the amount of carbon generated can be suppressed, and the fuel consumption can be reduced to improve combustion.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a piston manufactured by a method for manufacturing a combustion chamber according to the present invention.

FIG. 2 is an explanatory diagram for explaining one embodiment of a method for manufacturing a combustion chamber according to the present invention.

FIG. 3 is an explanatory view showing a state in which a lip assembly and a piston head main body are joined in the method of manufacturing the combustion chamber shown in FIG. 2;

FIG. 4 is an explanatory view showing another embodiment of the method for manufacturing a combustion chamber according to the present invention.

5 is an explanatory view showing a state in which the lip assembly and the piston head main body are joined in the method of manufacturing the combustion chamber shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Piston head main body 3 Combustion chamber opening 5 Cavity wall surface 6 Ring combination 7 Projection 8 Lip 9 Press jig 10 Cavity 16 Outer peripheral surface 17 Piston head upper surface 19 Inner wall surface 20 Lip assembly 21 Space 25 High frequency Coil 29 space

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 3/00 302 F02F 3/00 302Z 3/02 3/02 // B21K 25/00 B21K 25/00 Z (56) References Japanese Utility Model Application Showa 60-141446 (JP, U) Japanese Utility Model Application Showa 58-98455 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02F 3/00 F02F 3/00 301 F02F 3 / 00 302 F02F 3/02 F02F 3/26

Claims (2)

(57) [Claims] 1. A lip assembly made of a heat-resistant, high-strength ceramic material forming an opening in a combustion chamber is joined to the inner wall surface of a ring assembly made of a functionally graded material having a different coefficient of thermal expansion. Manufacturing, arranging the outer peripheral surface of the lip assembly on the wall surface of the cavity formed in the metal piston head main body, and then locally heating only the cavity wall surface portion of the piston head main body to perform the metal flow. Plastically deforming the lip assembly and joining the lip assembly to the piston head body. 2. A projecting portion projecting from an upper surface of the piston head body is formed on a wall surface portion of the cavity adjacent to the lip assembly, and a pressing jig is brought into contact with the projecting portion, and the pressing jig is set to a high frequency. The method for manufacturing a combustion chamber according to claim 1, wherein the heating locally heats only the protruding portion and a portion in the vicinity thereof, and the protruding portion undergoes metal flow and undergoes plastic deformation.