JPH04272457A - Structure of combustion chamber and its manufacture - Google Patents

Abstract

PURPOSE:To provide a structure of combustion chamber, in which a lip assembly made of a gradient functional material by metal flow process with an outer ring made of FRM(fiber-reinforced metal) rigidly and certainly. CONSTITUTION:A lip 8 made of a ceramic material with good high-temp. strength and heat resistance is joined with a ring coupling 7 made of a gradient functional material having different coefficients of thermal expansion, and an outer ring 6 made of FRM, in which metal wiskers having excellent magnetic characteristics are included, is subjected to high frequency heating and joined with a metal piston head body 2 by means of metal flow, and thus the outer ring 6 is plastically deformed locally by high frequency induction, and with this ring 6 the ring coupling 7 is joined.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure in which a lip is incorporated into a cavity formed in a piston head body to form a combustion chamber opening, and a method for manufacturing the same.

0002

2. Description of the Related Art Conventionally, there is a ceramic-integrated piston disclosed in Japanese Utility Model Application Publication No. 141446/1983. The ceramic-integrated piston disclosed in this publication has a ceramic member incorporated into a recess on the combustion chamber side of a piston body made of an aluminum alloy, and the outer periphery of the ceramic member has a thermal expansion coefficient of 10 to 23 x 10. -1
/°C heat-resistant and corrosion-resistant metal ring having a protruding part with a plurality of fastening holes on the head part, the protruding end is made to protrude from the upper end surface of the ceramic member, and the piston is attached to the outer periphery of the metal ring. This is an assembly in which a male threaded part is screwed into a female threaded part provided in a recessed part of the main body, and after this assembly is fastened to the piston main body, the protruding part including the fastening hole is removed. .

0003

[Problems to be Solved by the Invention] In the combustion chamber of a reentrant piston, if the tip of the lip of the combustion chamber inlet, that is, the opening of the combustion chamber, is formed to have a sharp point,
The turbulence of the squish flow and the reverse squish flow increases, the mixture of fuel and air becomes more uniform, and the combustion condition improves. However, with conventional aluminum pistons, problems such as melting of the lip and cracking occur due to the heat load applied to the lip that makes up the combustion chamber.
There was also a limit to how sharp the tip of the lip could be.

[0004] Furthermore, the ceramic built-in piston disclosed in the above-mentioned Japanese Utility Model Publication No. 1983-141446 has a metal ring fastened to a piston body made of an aluminum alloy with screws, and the metal ring is bonded to a ceramic member. However, metals and ceramics have different coefficients of thermal expansion, and in piston heads that are subjected to thermal stress, cracks and cracks occur in the ceramic members, causing the problem of damage to the ceramic members.

[0005] Conventionally, it has been developed to manufacture the lip portion of a reentrant piston from ceramics having high heat resistance. However, when the lip portion is made of ceramics, there is a problem in bonding it to the metal material that constitutes the piston head body. Ceramics and metals have different coefficients of thermal expansion, and when subjected to thermal load, a peeling state occurs due to the difference in coefficient of thermal expansion. Therefore, it is conceivable to place a functionally gradient material with a gradually different coefficient of thermal expansion between the lip part and the piston head body, but simply placing a functionally gradient material between the metal and the ceramic will not result in the same effect as the metal. It is not always possible to achieve reliable and strong bonding between the material and the functionally graded material.

An object of the present invention is to solve the above-mentioned problems, and the purpose of the present invention is to provide a combustion chamber in the center with a lip portion formed on an aluminum piston head body and whose top surface extends radially inward in the shape of a pointed ring. In the combustion chamber with an opening, the outer circumferential surface of the lip made of a ceramic material with high high-temperature strength and heat resistance is joined to the inner circumferential surface of a ring assembly made of a functionally graded material with a different coefficient of thermal expansion using metal flow, etc. Then, an outer ring made of fiber-reinforced metal (FRM) mixed with whiskers such as stainless steel is bonded to the aluminum wall of the cavity formed in the piston head body, and the wall made of fiber-reinforced metal is heated with high frequency. To provide a structure of a combustion chamber in which the lip assembly is heated to a higher temperature than the lip assembly, and the lip assembly is reliably and firmly joined to the outer ring by metal flow, and a method for manufacturing the same.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is,
The present invention relates to a metal piston head body forming a cavity, an outer ring made of a fiber-reinforced metal mixed with metal whiskers having excellent magnetic properties and reinforcing strength, and bonded to the cavity wall surface of the piston head body; A ring assembly made of functionally graded materials with different coefficients of thermal expansion bonded to the inner peripheral surface by metal flow, and a highly heat-resistant and high-strength material bonded to the inner peripheral surface of the ring assembly and forming the combustion chamber opening. The present invention relates to a structure of a combustion chamber including a lip portion made of a ceramic material.

[0008] Furthermore, the present invention has a lip part made of a highly heat-resistant and high-strength ceramic material, which forms a combustion chamber opening, bonded to the inner peripheral surface of a ring assembly made of functionally graded materials having different coefficients of thermal expansion. a step of manufacturing a lip assembly using a metal piston head body, a step of bonding an outer ring made of a fiber-reinforced metal mixed with metal whiskers having excellent magnetic properties and reinforcing strength to a cavity wall formed in a metal piston head body; The outer circumferential surface of the ring assembly is placed in contact with the inner circumferential surface of the ring, the outer ring body is heated to a higher temperature than the lip assembly by high frequency heating, and the ring assembly is attached to the outer ring body with metal. The present invention relates to a method for manufacturing a combustion chamber comprising a flow joining process.

[0009]

[Operation] The structure of the combustion chamber and the method for manufacturing the same according to the present invention are constructed as described above, and operate as follows. That is, the structure of this combustion chamber consists of a lip assembly made of functionally graded materials with different coefficients of thermal expansion, which is made of fiber-reinforced metal mixed with metal whiskers that have excellent magnetic properties and reinforce strength, bonded to a metal piston head body. Since the outer ring is joined by metal flow through the outer ring, the outer ring is firmly and reliably joined to the lip assembly.

[0010] In addition, this combustion chamber manufacturing method involves mixing a lip assembly made of functionally graded materials with different coefficients of thermal expansion with metal whiskers that have excellent magnetic properties and reinforce strength, bonded to a metal piston head body. Since they are joined by metal flow through an outer ring made of fiber-reinforced metal, by high-frequency heating of the outer ring, the metal whiskers, which have excellent magnetic properties and reinforce strength and are contained in aluminum or aluminum alloy, become heat conductive media. As a result, the outer ring heats up faster than the lip assembly and quickly reaches a temperature sufficient for metal flow. Therefore, only the outer ring is immediately plastically deformed by metal flow, and the lip assembly is reliably and firmly joined to the outer ring.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the structure of a combustion chamber and its manufacturing method according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the structure of a combustion chamber according to the present invention. This combustion chamber is formed in a piston head made of a metal material, and as shown in FIG.
The piston is formed in a reentrant type piston having a loop-shaped lip portion 8 extending radially inward in a pointed shape so as to cover the upper part of the combustion chamber 0 and having a combustion chamber opening 3. This piston consists of a piston head body 2 made of a metal material such as aluminum or aluminum alloy, which has a cast-molded piston skirt and a cavity 10 that is fixed to the piston skirt and constitutes a combustion chamber 1.
The combustion chamber 1 has an opening 3 on the upper surface of the cavity 10 and the opening 3
The bottom surface 4 of the cavity 10 has a larger area.

In particular, this combustion chamber has an outer ring 6 made of fiber-reinforced metal (FRM) mixed with metal whiskers that have excellent magnetic properties and reinforce strength, which is bonded to the cavity wall formed in the aluminum piston head body 2. ,
A ring assembly 7 made of functionally graded materials having different coefficients of thermal expansion in which the outer circumferential surface 19 is joined to the inner circumferential surface 22 of the outer ring 6 by metal flow; The opening 3 is formed by a lip portion 8 made of high-strength ceramics with excellent heat resistance.

In this reentrant type piston equipped with a combustion chamber, the lip portion 8 is made of a material having high heat resistance and high temperature strength, such as silicon nitride (Si3N4),
It is manufactured from a ceramic material such as silicon carbide (SiC). This lip portion 8 has a shape in which the tip forming the combustion chamber opening 3 is formed in a rounded shape with an extremely acute angle, and has a tapered surface 11 that slopes upward and downward in the radial direction with the outer circumferential surface 21 as a boundary at the center. It is manufactured in.

As shown in FIG. 2, the ring assembly 7 is composed of a plurality of (four in the figure) rings 12, 13, 14, and 15 that are sequentially arranged in the radial direction and whose adjacent peripheral surfaces are joined to each other. , is made from a functionally graded material in which the coefficient of thermal expansion of the inner ring is smaller than that of the outer ring. For example, the functionally graded material of the ring assembly 7 is made of a material having a coefficient of thermal expansion intermediate between the coefficients of thermal expansion of both the lip portion 8 and the piston head 2, such as a nickel-based, cobalt-based, or iron-based material. has been done. Specifically, the innermost ring 12
is made of Kover, 42 alloy, etc., the outermost ring 15 is made of Incoloy, and the middle rings 13 and 14 are made of a material with a coefficient of thermal expansion between Kovar and Incolloy. , each ring 12, 13, 14, 15 is joined by brazing or the like to form an integral structure. By manufacturing each ring with the above-mentioned material, the ring 1 located on the lip portion 8 side
2 can be made of a material with a coefficient of thermal expansion close to that of the lip portion 8, and the ring 15 located on the side of the piston head body 2 can be made of a material with a coefficient of thermal expansion close to that of the piston head body 2. It will be possible. Therefore, the ring assembly 7 is configured such that the coefficient of thermal expansion changes stepwise from the inner circumferential side to the outer circumferential side, ranging from a thermal expansion coefficient close to that of ceramic materials such as silicon nitride and silicon carbide to aluminum
It is configured to have a coefficient of thermal expansion close to that of metal materials such as aluminum alloys.

Furthermore, the outer ring 6 is made of a metal material equivalent to the metal material such as aluminum or aluminum alloy constituting the piston head body 2, and metal whiskers such as stainless steel SUS which have excellent magnetic properties and reinforce strength. Manufactured from blended fiber reinforced metal materials. The piston head body 2 is made of a metal material such as aluminum or an aluminum alloy, and is formed by casting the metal material such as aluminum or an aluminum alloy.

Next, the method for manufacturing a combustion chamber according to the present invention is as follows.
In particular, this will be explained with reference to FIGS. 2 and 3. As shown in FIG. 2, a ring assembly 7 is constructed by arranging a plurality of rings 12, 13, 14, 15 made of functionally graded materials having different coefficients of thermal expansion in sequence in the radial direction and joining adjacent peripheral surfaces to each other. Manufacture. At this time, the shape of the ring assembly 7 is formed such that the upper surface as a whole is horizontal and the lower surface is tapered so that the height of the outer ring 15 is higher than the height of the inner ring 12. A lip portion 8 made of a high-strength ceramic material with excellent heat resistance is provided on the inner circumferential surface 20 of the ring assembly 7.
The lip assembly 5 is manufactured by arranging the outer circumferential surface 21 of the lip assembly 5 and joining them together using metal flow or the like.

On the other hand, the wall surface of the cavity 10 of the aluminum piston head body 2 is made of fiber-reinforced metal FRM, which is made of an aluminum metal material mixed with metal whiskers such as stainless steel SUS that has excellent magnetic properties and reinforces strength. An outer ring 6 is joined. This outer ring 6 may be joined to the piston head main body 2 by beam welding, laser welding, etc., or may be joined into an integral structure during casting of the metal material of the piston head main body 2. A protruding portion 16 is formed on the upper wall surface of the outer ring 6 in order to cause the portion to undergo metal flow and plastic flow by high-frequency heating.

Next, the outer circumferential surface 19 of the ring combination 7 of the lip assembly 5 is placed on the inner circumferential surface 22 of the outer ring 6, and in this state, the protrusion 16 and its vicinity are subjected to high frequency heating using the high frequency coil 17. The protrusion 16 is pressed with a press jig 18. Since the outer ring 6 contains metal whiskers with excellent magnetic properties, when high-frequency heating is performed, the outer ring 6 is rapidly heated to a high temperature state compared to the ring combination 7 due to high-frequency induction. The temperature is immediately raised to a temperature sufficient for metal flow. Therefore, only the outer ring 6 is in a metal flow state and plastically deformed, and the plastically flowed metal material fills the gap formed between the outer circumferential surface 19 of the lip assembly 5 and the inner circumferential surface 22 of the outer ring 6. Invade 9. Therefore, the lip assembly 5 is firmly and reliably joined to the outer ring 6.

Since the structure of the combustion chamber and the method for manufacturing the same according to the present invention are constructed as described above, they function 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 assembly 7 made of functionally graded materials with different coefficients of thermal expansion acts as a buffer material and absorbs the difference in thermal expansion caused by the temperature difference between the lip portion 8, the outer ring 6, and the piston head body 2. 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 body 2, cracks or cracks will not occur in the lip portion 8, and the combustion chamber 1 will remain stable. It will never be destroyed. In addition, the lip portion 8 has a pointed, acute-angled shape and allows a large amount of heat to flow from the combustion gas.
It flows unhindered in the two directions of the piston head body through the piston head body, and flows out to the cylinder liner side through the piston skirt, piston ring, etc. Therefore, the temperature rise is suppressed without maintaining the temperature of the lip portion 8 at a high temperature, so even if the edge of the lip portion 8 is configured to have an acute pointed shape, the edge is made with heat resistance. will not melt or break.

Furthermore, since the lip portion 8 is made of a material such as ceramics which has a low coefficient of thermal expansion and is highly heat resistant, the edge of the lip portion 8 that forms the combustion chamber opening 3 is formed at an extremely acute angle and the shape is can be maintained even at high temperatures. Therefore, it is possible to increase the squish flow that occurs during the compression stroke of the piston's upward movement and the reverse squish flow that occurs during the piston's downward explosion stroke, promoting the mixing of air and fuel, suppressing the amount of carbon generated, and reducing the amount of fuel. It is possible to perform combustion that reduces consumption and improve combustion conditions.

[0021]

[Effects of the Invention] The structure of the combustion chamber and the method of manufacturing the same according to the present invention, constructed as described above, have the following effects. That is, the structure of this combustion chamber consists of an outer ring made of a fiber-reinforced metal mixed with metal whiskers that have excellent magnetic properties and reinforce strength, bonded to the wall surface of a cavity formed in an aluminum piston head body, and an inner periphery of the outer ring. A ring assembly made of functionally graded materials with different coefficients of thermal expansion bonded to the surface by metal flow, and made of a high-strength ceramic material with high heat resistance that is bonded to the inner peripheral surface of the ring assembly and forms the combustion chamber opening. The outer ring is firmly and reliably joined to the lip assembly. Heat flow from the tip to the piston head at the outer periphery of the lip portion at each boundary is unobstructed and is well conducted, so that the heat at the tip of the lip portion is transferred to the outer periphery of the piston head, the piston ring, It is possible to move the lip part to the outside through a cylinder liner or the like to avoid the lip part from becoming high temperature and prevent the lip part from being melted due to high temperature. It is possible to absorb the difference in thermal expansion and avoid cracking of the lip portion even if thermal stress is applied due to the temperature difference. Therefore, even if the tip of the lip portion is formed to be pointed at an acute angle, even if the tip becomes hot due to combustion gas, the heat is immediately transferred to avoid being maintained at a high temperature, It is possible to prevent the distal end portion from melting due to high temperatures.

Further, in this combustion chamber, the ring assembly is made of functionally graded materials having different coefficients of thermal expansion, so that the difference in thermal expansion between the lip portion, the outer ring, and the piston head body can be reduced in a sloped manner. The thermal stress generated due to the temperature difference is gradually reduced in an inclined manner, and cracks in the lip portion can be effectively avoided.

Furthermore, by forming the lip portion from a material with high heat resistance, even if the lip portion is formed to have an acute point, the tip portion, that is, the edge of the lip portion can be prevented from being melted and damaged, and the sharp point can be prevented from melting. The edge shape of the state can be maintained. Therefore, the lip portion can be formed to have an acute angle, and by forming the edges of the lip portion at an acute angle, the squish flow flowing into the combustion chamber that occurs during the compression stroke of the upward movement of the piston, and the explosion stroke of the downward movement of the piston, can be prevented. It is possible to increase the reverse squish flow flowing out from the combustion chamber generated in , it is possible to improve combustion by suppressing the amount of carbon generated and reducing fuel consumption. In particular, when this reentrant piston is used in a direct injection diesel engine, the combustion state of the engine can be improved.

Alternatively, the method for manufacturing a combustion chamber according to the present invention is to form a combustion chamber opening on the inner circumferential surface of a ring assembly made of functionally graded materials having different coefficients of thermal expansion. The process of manufacturing a lip assembly by joining the lip parts made of aluminum piston head body, and joining the outer ring made of fiber-reinforced metal mixed with metal whiskers that have excellent magnetic properties and strengthen strength to the cavity wall formed in the aluminum piston head body. arranging the outer peripheral surface of the ring assembly on the inner peripheral surface of the outer ring, heating the outer ring body to a higher temperature than the lip assembly by high frequency heating, and placing the ring assembly on the outer ring body. The lip assembly is made of functionally graded materials with different coefficients of thermal expansion and is bonded to the aluminum piston head body using a process in which the body is joined using metal flow.The lip assembly is made of fibers mixed with metal whiskers that have excellent magnetic properties and reinforce strength. Since they are joined by metal flow through an outer ring made of reinforcing metal, when the outer ring is heated with high frequency, the metal whiskers contained in aluminum or aluminum alloy, which have excellent magnetic properties and reinforce strength, become a heat conductive medium. The outer ring heats up faster than the lip assembly and quickly reaches a temperature sufficient for metal flow.

That is, in general, the temperature of aluminum materials is difficult to rise, but since fiber-reinforced metal materials contain metal whiskers with excellent magnetic properties, by high-frequency heating, the outer ring can be heated to a high temperature immediately by high-frequency induction. Become. Further, the ring assembly made of a functionally graded material is also made of a material whose temperature does not easily rise compared to the outer ring. Therefore,
The temperature difference between the outer ring and the lip assembly increases, and only a predetermined portion of the outer ring immediately locally increases in temperature, causing metal flow and becoming plastically deformable. Since the solid body is not in the metal flow state and both are not in the metal flow state at the same time, the outer ring is plastically deformed with respect to the lip assembly, and the two are reliably and firmly joined.

[Brief explanation of the drawing]

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

FIG. 2 is an explanatory diagram illustrating a step before joining the lip assembly and the outer ring in the combustion chamber manufacturing method according to the present invention.

FIG. 3 is an explanatory diagram showing a state in which the lip assembly and the outer ring are joined in the method for manufacturing a combustion chamber according to the present invention.

[Explanation of symbols]

1 Combustion chamber 2 Piston head body 5 Lip assembly 6 Outer ring 7 Ring combination 8 Lip part 9 Vacancy 10 Cavity 19 Outer peripheral surface 20 Inner peripheral surface 22 Inner peripheral surface

Claims (2)

[Claims] 1. A metal piston head body forming a cavity, an outer ring made of a fiber-reinforced metal mixed with metal whiskers having excellent magnetic properties and reinforcing strength and bonded to the cavity wall surface of the piston head body, the outer ring. A ring assembly made of functionally graded materials with different coefficients of thermal expansion joined by metal flow to the inner peripheral surface of the ring assembly, and a high-strength, heat-resistant material joined to the inner peripheral surface of the ring assembly and forming a combustion chamber opening. The structure of the combustion chamber consists of a lip part made of ceramic material. 2. A lip assembly is obtained by bonding a lip portion made of a highly heat-resistant and high-strength ceramic material that forms a combustion chamber opening to the inner peripheral surface of a ring assembly made of functionally graded materials having different coefficients of thermal expansion. a step of bonding an outer ring made of fiber-reinforced metal mixed with metal whiskers having excellent magnetic properties and reinforcing strength to a cavity wall surface formed in a metal piston head body; and an inner circumferential surface of the outer ring. , the outer peripheral surfaces of the ring assembly are placed in contact with each other, the outer ring body is heated to a higher temperature than the lip assembly by high frequency heating, and the ring assembly is joined to the outer ring body by metal flow. A method of manufacturing a combustion chamber consisting of .