Composite piston, forming device and forming method

Abstract

The composite piston comprises an aluminum piston body and a prefabricated part, a combustion chamber is formed in the head of the aluminum piston body, the prefabricated part is embedded in the combustion chamber to form the composite piston which is locally or completely covered, and when the aluminum piston body is formed, molten aluminum of the aluminum piston body is infiltrated into the prefabricated part to form an aluminum-based composite material; a forming device of a composite piston comprises an upper die, a lower die, an extrusion casting punch and an injection assembly, a prefabricated part is installed on the lower die, an annular part is further installed on the lower die, the upper die and the extrusion casting punch move downwards to press the annular part, and a cavity of an aluminum piston body is defined by the upper die and the extrusion casting punch and the prefabricated part. The injection assembly is located below the lower die and injects aluminum liquid into the cavity to be pressurized to form a composite piston. The invention discloses a forming method of a composite piston. The mold has the advantages of simple structure, easiness in molding, high molding quality and high heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of pistons, and in particular to a composite piston, a molding device and a molding method. Background Art

[0002] The piston is an important component of the internal combustion engine. Aluminum alloy pistons are widely used due to their light weight and low inertia. When the piston is working, the throat, top and bottom of the combustion chamber of the piston head are subjected to high operating temperatures and heavy alternating loads. Throat cracking and burning of the top and combustion chamber become the main failure modes. In order to improve the heat resistance of the piston top and combustion chamber and prevent cracking and ablation, forming a composite material on the top of the aluminum alloy piston has become an important process method, such as: Application No. 202011428476.7 Whisker reinforced aluminum alloy piston and preparation method, the first ring groove, top surface and throat of the piston are whisker reinforced to improve the heat resistance of the piston top and throat, but this structure and forming method have the following problems:

[0003] First, during molding, metal oxide impurities accumulate upward on the aluminum borate whisker preform, reducing the molding quality of the reinforcement and piston top. Second, when the metal liquid piston head is injected into the mold cavity, the aluminum liquid erodes the inserts and core, reducing the molding quality of the cooling cavity of the composite piston casting. Third, to achieve a good filling effect, the center of the aluminum borate whisker preform must have a large pouring aperture, making it difficult for the preform to effectively extend and cover the combustion chamber. The hole wall in the center of the aluminum borate whisker preform is prone to adhesion and adsorption of metal oxide impurities, reducing the molding quality of the interface between the preform and the aluminum alloy body. As the explosion pressure of internal combustion engines continues to increase, higher requirements are placed on the heat resistance of the piston. Local reinforcement of key piston locations cannot fully solve the cracking and ablation problems caused by high temperature and low heat resistance of the material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a composite piston, a molding device and a molding method which are simple in structure, easy to mold, high in molding quality and strong in heat resistance.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A composite piston comprises an aluminum piston body and a prefabricated part. A combustion chamber is formed on the head of the aluminum piston body. The prefabricated part is embedded in the combustion chamber to form a composite piston that partially or fully covers the combustion chamber. When the aluminum piston body is formed, aluminum liquid infiltrates into the prefabricated part to form an aluminum-based composite material.

[0007] As a further improvement of the above technical solution:

[0008] The prefabricated part is aluminum borate / magnesium fiber or foamed silicon carbide. When the aluminum piston body is formed, the aluminum liquid infiltrates into the prefabricated part to form a reinforced aluminum-based composite material.

[0009] The prefabricated part is configured in an annular tube shape, and the prefabricated part and the central top of the aluminum piston body together constitute the combustion chamber.

[0010] The preform is configured in the shape of an annular plate, and the combustion chamber is formed on the top of the preform.

[0011] It also includes a covering part, which is set to a heat-resistant metal. The covering part covers the central top of the aluminum piston body and overlaps with the prefabricated part. The covering part is formed with a stud, which is passed through the aluminum piston body and is fixed by a nut.

[0012] A positioning shaft is also formed on the prefabricated part, and the positioning shaft is embedded in the top of the aluminum piston body to form a hole-shaft fit and bite at the embedded part.

[0013] It also includes a covering member, which is made of heat-resistant metal. The covering member covers the top of the preform and is fixedly connected to the preform, and the combustion chamber is formed on the top of the covering member.

[0014] The cover is formed with a stud, which is embedded in the top of the prefabricated part and forms a cone-type locking fit at the embedded position.

[0015] The covering part and the preform are fitted together, and a conical locking fit is formed at the fitting portion. A groove is formed on the covering part, and the top edge of the preform is fitted into the groove. A conical surface is formed in the groove. A stud is formed on the covering part, and the stud is passed through the preform and the aluminum piston body and is fixed by a nut.

[0016] A forming device for a composite piston comprises an upper die, a lower die, an extrusion-casting punch and an injection assembly, wherein the preform is mounted on the lower die, and an annular member is also mounted on the lower die, wherein the upper die and the extrusion-casting punch move downward to compress the annular member and enclose the preform to form a cavity for an aluminum piston body, wherein the injection assembly is located below the lower die and fluidly injects aluminum into the cavity to pressurize and form a composite piston, and a guide member is detachably mounted on the lower die to facilitate separation of the material handle of the composite piston from the aluminum piston body after the composite piston is formed.

[0017] As a further improvement of the above technical solution:

[0018] A locking piece is provided on the lower die, the flow guide is embedded in the lower die and is locked and fixed by the locking piece, and a slot corresponding to the locking piece is provided on the flow guide.

[0019] The guide member is provided with a through hole which is perpendicular to the parting surface of the cavity and serves as an inner gate. The through hole is arranged as a variable diameter structure which is small in the middle and large at both ends. A groove is formed in the middle of the through hole. A retaining ring is installed in the groove which forms a dividing flange between the material handle and the aluminum piston body after molding.

[0020] The injection assembly includes a barrel, which is in the lower die and connected to the cavity through a through hole. An injection punch for injecting aluminum liquid from the through hole into the cavity is provided in the barrel.

[0021] The lower die is provided with a positioning piece for positioning and installing the composite piston ring.

[0022] A method for forming a composite piston, using a forming device for extrusion casting, comprises the following steps:

[0023] S1: Preheat the upper die, lower die and extrusion punch, and then install the guide piece and ring piece on the lower die;

[0024] S2: Install the prefabricated part on the lower mold and install the insert ring through the positioning piece;

[0025] S3: The upper die and the extrusion punch move downward to close the lower die and press the ring part to form a cavity;

[0026] S4: Add aluminum liquid into the barrel, and inject the aluminum liquid into the cavity through the through hole through the injection punch, and pressurize at a low speed to form a composite piston casting;

[0027] S5: The upper die and the extrusion punch move downward further and compress the ring and the composite piston casting to deform;

[0028] S6: The upper die and the extrusion punch move up, and the injection punch pushes the material handle, the guide piece and the composite piston casting to move up together and separate from the lower die;

[0029] S7: Drill and mill the material handle, cut off the connection between the material handle and the aluminum piston body at the clamping ring, and then separate the aluminum piston body, the material handle and the guide piece.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] Compared with existing pistons, the aluminum piston body of the present invention is extrusion-cast, and a prefabricated part is embedded in its head to form a composite piston. It has a simple structure and is easy to form. When the aluminum piston body is formed, the aluminum liquid infiltrates into the prefabricated part to form an aluminum-based composite material to strengthen the piston head and the throat of the combustion chamber, thereby improving the piston head's ability to withstand relatively variable loads and the combustion chamber's heat resistance, and avoiding cracking and burning of the piston head.

[0032] The molding device of the present invention, during molding, the upper mold and the extrusion casting punch move downward to compress the ring part and the preform on the lower mold to form a mold cavity, and the aluminum liquid is hydraulically injected into the mold cavity through the injection assembly to form a composite piston casting. Compared with the traditional vertical indirect extrusion casting molding device, the lower mold is provided with a guide member, and the guide member is integrally formed with the composite piston casting during extrusion casting, and a material handle is formed between the injection assembly and the guide member. The molten metal directly enters the mold cavity under pressure through the guide member, and the injection pressure loss is small, which is conducive to the filling of the composite piston casting and the shrinkage compensation and crystallization under pressure, thereby ensuring the quality of the composite piston casting; during molding, the upper mold and the extrusion casting punch move downward to compress the ring part and the composite piston casting to produce slight plastic deformation, thereby further improving the mechanical properties of the composite piston casting.

[0033] This method uses an injection punch to inject molten aluminum from a barrel through a through hole into the middle of the cavity after the mold is closed to form a cavity, and then diverts the aluminum liquid into the cavity. This can reduce the erosion of the inlays and core by the molten aluminum, and improve the molding quality of the composite piston casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram (cross-sectional view) of the overall structure of Example 1 of the present invention.

[0035] Figure 2 It is a schematic diagram (cross-sectional view) of the overall structure of Example 2 of the present invention.

[0036] Figure 3 2 is a schematic diagram (sectional view) of the prefabricated structure of Example 2 of the present invention.

[0037] Figure 4 It is a schematic structural diagram (cross-sectional view) of the cover member according to embodiment 2 of the present invention.

[0038] Figure 5 It is a schematic diagram (cross-sectional view) of the overall structure of Example 3 of the present invention.

[0039] Figure 6 2 is a schematic diagram (sectional view) of the prefabricated structure of Example 3 of the present invention.

[0040] Figure 7 It is a schematic diagram (cross-sectional view) of the overall structure of embodiment 4 of the present invention.

[0041] Figure 8 2 is a schematic diagram (sectional view) of the prefabricated structure of Example 4 of the present invention.

[0042] Figure 9 It is a schematic structural diagram (cross-sectional view) of the cover member according to embodiment 4 of the present invention.

[0043] Figure 10 It is a schematic diagram (cross-sectional view) of the overall structure of Example 5 of the present invention.

[0044] Figure 11 2 is a schematic diagram (sectional view) of the prefabricated structure of Example 5 of the present invention.

[0045] Figure 12 It is a schematic structural diagram (cross-sectional view) of the cover member according to embodiment 5 of the present invention.

[0046] Figure 13 It is a structural schematic diagram of the molding device of the present invention (before molding).

[0047] Figure 14 It is a structural schematic diagram of the molding device of the present invention (after molding).

[0048] Figure 15 It is a schematic structural diagram (cross-sectional view) of the flow guide of the present invention.

[0049] The numbers in the figure represent:

[0050] 1. Aluminum piston body; 11. Material handle; 2. Prefabricated part; 21. Protective plate; 22. Positioning shaft; 23. Conical hole groove; 3. Combustion chamber; 4. Cover; 41. Stud; 42. Groove; 421. Conical surface; 5. Nut; 6. Upper die; 7. Lower die; 71. Guide piece; 711. Through hole; 712. Snap ring; 72. Locking piece; 73. Positioning piece; 8. Extrusion punch; 9. Injection assembly; 91. Barrel; 92. Injection punch; 100. Cavity; 101. Ring part. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Example 1:

[0053] like Figure 1 As shown, the first embodiment of the composite piston of the present invention includes an aluminum piston body 1 and a preform 2. The head of the aluminum piston body 1 is formed with a combustion chamber 3. The preform 2 is embedded in the combustion chamber 3 to form a composite piston that partially covers the combustion chamber 3. The composite piston head is formed with the combustion chamber 3. When the aluminum piston body 1 is formed, its molten aluminum infiltrates into the preform 2 to form an aluminum-based composite material. Compared with existing pistons, the aluminum piston body 1 of the present invention is formed by extrusion casting, and its head is embedded with the preform 2 to form a composite piston. It has a simple structure and is easy to form. When the aluminum piston body 1 is formed, its molten aluminum infiltrates into the preform 2 to form an aluminum-based composite material to strengthen the piston head and the throat of the combustion chamber 3. The aluminum-based composite material has good rigidity, stable structure, and strong supporting force, which improves the piston head's ability to withstand relatively variable loads and the heat resistance of the combustion chamber 3, thereby preventing the piston head from cracking and ablation.

[0054] In this embodiment, preform 2 is a ceramic fiber composed of aluminum borate fibers. During the molding of the aluminum piston body 1, molten aluminum infiltrates the ceramic fibers to form a ceramic-reinforced aluminum-based composite material. This composite material exhibits high strength, good rigidity, and excellent heat resistance. In other embodiments, preform 2 can also be made of foamed silicon carbide or magnesium borate fibers.

[0055] In this embodiment, the preform 2 is configured as an annular tube, and the top of the preform 2 and the center top of the aluminum piston body 1 together form a combustion chamber 3. The structure is simple and easy to install.

[0056] like Figures 13 to 15 As shown, the forming device of the composite piston of this embodiment includes an upper mold 6, a lower mold 7, an extrusion punch 8 and an injection assembly 9. The preform 2 is installed on the lower mold 7. The upper mold 6 and the extrusion punch 8 move downward to press the annular part 101 and the preform 2 to form a cavity 100 for the aluminum piston body 1. The injection assembly 9 is located below the lower mold 7 and hydraulically injects aluminum into the cavity 100 to pressurize it to form a composite piston. The lower mold 7 is detachably equipped with a guide member 71 for facilitating the separation of the material handle 11 of the composite piston from the aluminum piston body 1 after the composite piston is formed. During molding, the upper mold 4 and the extrusion punch 8 move downward to compress the ring part 101 and the preform 2 on the lower mold 7 to form a mold cavity 100, and the aluminum liquid is hydraulically injected into the mold cavity 100 through the injection assembly 9 to form a composite piston casting. Compared with the traditional vertical indirect extrusion casting molding device, its lower mold 7 is provided with a guide part 71 and a through hole 711. The molten metal directly enters the mold cavity 100 under pressure, and the injection pressure loss is small, which is conducive to the filling of the composite piston casting and the shrinkage compensation and crystallization under pressure, thereby ensuring the quality of the composite piston casting.

[0057] In this embodiment, the parting surface between the upper mold 6 and the lower mold 7 is provided with an annular groove, in which an annular part 101 that is easily deformed under pressure is installed. During high-pressure shrinkage compensation and crystallization, the upper mold 6 and the extrusion punch 8 move downward to compress the annular part 101 to deform so as to reduce the longitudinal height and volume of the cavity 100. The aluminum piston body 1 produces a slight plastic deformation under pressure, further improving the quality and mechanical properties of the composite piston casting formed by indirect extrusion casting.

[0058] In this embodiment, the guide member 71 is integrally formed with the composite piston casting during extrusion casting, forming a material handle 11 between the injection assembly 9 and the guide member 71. The material handle 11, the aluminum piston body 1, and the guide member 71 are separated at the guide member 71 by mechanical processing, making operation convenient and the guide member 71 reusable. In this embodiment, a locking member 72 is provided through the lower mold 7. The guide member 71 is embedded in the lower mold 7 and locked and fixed by the locking member 72. The guide member 71 is provided with a slot corresponding to the locking member 72. In this structure, the guide member 71 is provided with a slot on its outer periphery. After being embedded in the lower mold 7, the guide member 71 is locked to the lower mold 7 by inserting the locking member 72 into the slot.

[0059] In this embodiment, a through hole 711 is provided on the flow guide 71, which is perpendicular to the parting surface of the cavity 100 and serves as an ingrown gate. The through hole 711 is configured as a variable diameter structure with a small center and large ends. A groove is formed in the middle of the through hole 711, and a retaining ring 712 is installed in the groove, which forms a boundary flange between the material handle 11 and the aluminum piston body 1 after molding. In this structure, the through hole 711 is provided in the middle of the flow guide 71 as an ingrown gate. The through hole 711 connects to the middle of the cavity 100, shortening the filling distance of the molten aluminum in the cavity 100 during extrusion casting, facilitating the filling, slag removal, exhaust, and sequential solidification of the cavity 100. The through hole 711 is located below the extrusion punch 8, which facilitates the diversion and balanced filling of the molten metal, thereby improving the filling quality of the molten metal. The through hole 711 is set as a variable diameter structure, a groove is formed in the middle thereof and a retaining ring 712 is installed, so that the retaining ring 712 forms a dividing flange between the material handle 11 and the aluminum piston body 1. The retaining ring 712 is a consumable part, and drilling and milling processing is performed directly at the retaining ring 712, which is conducive to the separation of the guide member 71 and the aluminum piston body 1.

[0060] In this embodiment, the injection assembly 9 includes a barrel 91, which is located within the lower die 7 and communicates with the mold cavity 100 via a through-hole 711. A shot punch 92 is located within the barrel 91 for injecting molten aluminum from the through-hole 711 into the mold cavity 100. In this structure, a hydraulic cylinder is used to push the shot punch 92 to inject the molten aluminum in the barrel 91 through the through-hole 711 into the mold cavity 100. This structure is simple, and the pressure loss of the shot punch 92 is minimal, ensuring balanced performance of the composite piston casting.

[0061] In this embodiment, a positioning member 73 for positioning and installing a composite piston insert is provided on the lower die 7. In this structure, the positioning member 73 is provided on the lower die 17 to facilitate the installation of the insert, and as for the core, it is installed on the extrusion punch 8.

[0062] The forming method of the composite piston of this embodiment includes the following steps:

[0063] S1: Preheat the upper die 6, the lower die 7 and the extrusion punch 8, and then install the guide member 71 and the ring member 101 on the lower die 7;

[0064] S2: Install the preform 2 on the lower mold 7 and install the insert ring through the positioning member 73;

[0065] S3: The upper die 6 and the extrusion punch 8 move downward to close the lower die 7 and press the ring 101 to form a cavity 100;

[0066] S4: Add aluminum liquid into the barrel 91 and inject the aluminum liquid into the mold cavity 100 through the through hole 711 through the injection punch 92, and pressurize at a low speed to form a composite piston casting;

[0067] S5: the upper die 6 and the extrusion punch 8 move further downward and compress the ring 101 and the composite piston casting to deform;

[0068] S6: The upper die 6 and the extrusion punch 8 move upward, and the injection punch 92 pushes the material handle 11, the flow guide 71 and the composite piston casting upward and separates from the lower die 7;

[0069] S7: The material handle 11 is drilled and milled to cut off the connection between the material handle 11 and the aluminum piston body 1 at the clamping ring 712, and then the aluminum piston body 1, the material handle 11 and the guide member 71 are separated.

[0070] After the mold is closed to form the mold cavity 100, the present method uses the injection punch 92 to inject the aluminum liquid from the barrel 91 through the through hole 711 into the mold cavity 100, and then pressurizes the composite piston casting at a low speed, so that the aluminum liquid fills the mold at a low speed in the mold cavity 100, which can reduce the cracking caused by the erosion of the aluminum liquid on each embedded component and improve the molding quality of the composite piston. The pressure of the injection punch 92 is transmitted to the aluminum liquid in the mold cavity 100 through the aluminum liquid in the through hole 711, and then pressurizes and feeds the shrinkage, so that the composite piston casting forms a better dense metal structure.

[0071] During extrusion molding, the aluminum liquid flows into the through hole 711, then enters the cavity 100 from the middle of the preform 2 and fills the cavity 100. At the same time, the aluminum liquid penetrates into the preform 2 to form a composite piston. The extrusion punch 8 also plays the role of diverting the aluminum liquid, and the filling effect is good.

[0072] Example 2:

[0073] like Figures 2 to 4 As shown, the second embodiment of the composite piston of the present invention is basically the same as the first embodiment, except that:

[0074] This embodiment also includes a cover member 4 made of a heat-resistant metal. Cover member 4 is installed and covers the center top of the aluminum piston body 1, and overlaps with preform 2. In this structure, preform 2 has strong heat resistance and good rigidity, and the overlap structure is stable. Together with cover member 4, it forms a complete and heat-resistant surface, further improving the heat resistance of the overall structure of combustion chamber 3.

[0075] In this embodiment, a stud 41 is formed on the cover 4, and the stud 41 is passed through the aluminum piston body 1 and is locked and fixed by a nut 5. It has a simple structure and a stable connection.

[0076] In this embodiment, the cover 4 is made of a heat-resistant metal having a thermal expansion coefficient close to that of the aluminum piston body 1 , thereby reducing the difference in thermal expansion deformation and facilitating the fixing of the stud 41 to the aluminum piston body 1 .

[0077] Example 3:

[0078] like Figures 5 and 6As shown, the third embodiment of the composite piston of the present invention is basically the same as the first embodiment, with the only difference being:

[0079] In this embodiment, the preform 2 is configured as a ring plate, and a combustion chamber 3 is formed on the top of the preform 2. The structure is simple, and the head of the aluminum piston body 1 is fully covered and strengthened.

[0080] In this embodiment, a protective plate 21 is provided on the preform 2, and the protective plate 21 is located in the middle of the combustion chamber 3. The protective plate 21 is provided to reduce the erosion of the metal aluminum liquid during the extrusion forming of the aluminum piston body 1 and absorb oxide impurities.

[0081] In this embodiment, the preform 2 is further formed with a positioning shaft 22, which is embedded in the top of the aluminum piston body 1 and forms a hole-shaft engagement at the embedding portion. This has a simple structure and strengthens the embedding and fixed connection between the preform 2 and the aluminum piston body 1.

[0082] Example 4:

[0083] like Figures 7 to 9 As shown, the fourth embodiment of the composite piston of the present invention is basically the same as the first embodiment, with the only difference being:

[0084] In this embodiment, the preform 2 is configured to be in the shape of an annular plate and further includes a covering member 4 , which is installed inside the preform 2 .

[0085] In this embodiment, the cover 4 is formed with a stud 41, which is installed in the tapered hole 23 of the preform 2 and forms a tapered locking fit with the preform 2 at the fitting portion.

[0086] In this embodiment, the cover 4 is made of heat-resistant metal and has a groove 42 formed therein. The top of the preform 2 fits into the groove 42. A conical surface 421 is formed in the groove 42. The molten aluminum infiltrates into the preform 2 to form an aluminum-based composite material with a thermal expansion coefficient similar to that of the cover 4. The composite material forms a tapered locking fit with the conical surface 421. This structure is simple and reliable.

[0087] Example 5:

[0088] like Figures 10 to 12 As shown, the fifth embodiment of the composite piston of the present invention is basically the same as the first embodiment, with the only difference being:

[0089] In this embodiment, the preform 2 is configured as an annular plate and is fitted with a cover 4 constructed of a heat-resistant metal. The cover 4 covers the top of the preform 2 and is fixedly connected to the preform 2 and the aluminum-based composite material. A combustion chamber 3 is formed on the top of the cover 4. In this structure, the provision of the cover 4 made of a heat-resistant metal further enhances the heat resistance and load-bearing capacity of the overall structure. In this embodiment, the cover 4 is locally heated and installed to cover the preform 2. The molten aluminum infiltrates into the preform 2 to form an aluminum-based composite material with a thermal expansion coefficient similar to that of the cover 4. The top of the preform 2 is embedded in a groove 42 provided in the cover 4, and the preform 2 forms a conical locking fit with the tapered surface 421 at the bottom outer edge of the cover 4. The installation is simple and the inlay connection is reliable.

[0090] In this embodiment, studs 41 are formed on the cover 4. Studs 41 are inserted through the preform 2 and the aluminum piston body 1 and are locked and fixed by nuts 5. The studs 41 and nuts 5 further lock and secure the cover 4, eliminating fatigue failure caused by impact at the contact surface between the cover 4 and the preform 2.

[0091] Although the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, utilize the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A composite piston, characterized in that: The invention comprises an aluminum piston body (1) and a preform (2); a combustion chamber (3) is formed on the head of the aluminum piston body (1); the preform (2) is embedded in the combustion chamber (3) to form a composite piston that partially or fully covers the combustion chamber; when the aluminum piston body (1) is formed, aluminum liquid infiltrates into the preform (2) to form an aluminum-based composite material.

2. The composite piston according to claim 1, characterized in that: The preform (2) is aluminum borate / magnesium fiber or foamed silicon carbide, and when the aluminum piston body (1) is formed, the aluminum liquid is infiltrated into the preform (2) to form a reinforced aluminum-based composite material.

3. The composite piston according to claim 2, characterized in that: The preform (2) is configured in an annular tube shape, and the preform (2) and the central top of the aluminum piston body (1) together form the combustion chamber (3).

4. The composite piston according to claim 2, characterized in that: The preform (2) is configured as a ring plate, and the combustion chamber (3) is formed on the top of the preform (2).

5. The composite piston according to claim 3, characterized in that: The preform (2) is overlapped with the cover (4), and a stud (41) is formed on the cover (4). The stud (41) is passed through the aluminum piston body (1) and is locked and fixed by a nut (5).

6. The composite piston according to claim 4, characterized in that: A positioning shaft (22) is also formed on the preform (2), and the positioning shaft (22) is embedded in the top of the aluminum piston body (1) and forms a hole-shaft fit and bite at the embedded position.

7. The composite piston according to claim 4, characterized in that: It also includes a covering member (4), which is configured as a heat-resistant metal. The covering member (4) covers the top of the preform (2) and is fixedly connected to the preform (2). The combustion chamber (3) is formed on the top of the covering member (4).

8. The composite piston according to claim 7, characterized in that: A stud (41) is formed on the cover (4), and the stud (41) is embedded in the top of the preform (2) and forms a conical locking fit at the embedded position.

9. The composite piston according to claim 7, characterized in that: The covering part (4) and the preform (2) are interlocked with each other and form a conical locking fit at the interlocking portion. A groove (42) is formed on the covering part (4), and the top edge of the preform (2) is interlocked in the groove (42). A conical surface (421) is formed in the groove (42). A stud (41) is formed on the covering part (4), and the stud (41) is passed through the preform (2) and the aluminum piston body (1) and is locked and fixed by a nut (5).

10. A molding device for a composite piston according to any one of claims 1 to 9, characterized in that: The invention comprises an upper die (6), a lower die (7), an extrusion punch (8) and an injection assembly (9); the preform (2) is mounted on the lower die (7); an annular member (101) is further mounted on the lower die (7); the upper die (6) and the extrusion punch (8) move downward to press the annular member (101) and enclose the annular member (101) with the preform (2) to form a cavity (100) of an aluminum piston body (1); the injection assembly (9) is located below the lower die (7) and fluidly injects aluminum into the cavity (100) to pressurize the composite piston; the lower die (7) is detachably provided with a flow guide (71) for facilitating the separation of the material handle (11) of the composite piston from the aluminum piston body (1) after the composite piston is formed.

11. The forming device according to claim 10, characterized in that: The lower mold (7) is provided with a locking piece (72), the flow guide (71) is embedded in the lower mold (7) and is locked and fixed by the locking piece (72), and the flow guide (71) is provided with a slot corresponding to the locking piece (72).

12. The forming device according to claim 11, characterized in that: The guide member (71) is provided with a through hole (711) which is perpendicular to the parting surface of the cavity (100) and serves as an inner gate. The through hole (711) is configured as a variable diameter structure with a small middle portion and large ends. A groove is formed in the middle of the through hole (711). A retaining ring (712) is installed in the groove to form a boundary flange between the material handle (11) and the aluminum piston body (1) after molding.

13. The forming device according to claim 12, characterized in that: The injection assembly (9) comprises a barrel (91), which is inside the lower die (7) and communicates with the die cavity (100) through a through hole (711). An injection punch (92) for injecting aluminum liquid from the through hole (711) into the die cavity (100) is provided inside the barrel (91).

14. The forming device according to claim 13, characterized in that: The lower die (7) is provided with a positioning piece (73) for positioning and installing the composite piston ring.

15. A method for forming a composite piston according to any one of claims 1 to 9, characterized in that: Squeeze casting is performed using a molding device according to any one of claims 10 to 14, The following steps are involved: S1: preheating the upper die (6), the lower die (7) and the extrusion punch (8), and then installing the guide member (71) and the ring member (101) on the lower die (7); S2: Install the preform (2) on the lower mold (7) and install the insert ring through the positioning member (73); S3: the upper die (6) and the extrusion punch (8) move downward to close the die with the lower die (7) and press the annular member (101) to form a cavity (100); S4: adding aluminum liquid into the barrel (91), and injecting the aluminum liquid from the through hole (711) into the mold cavity (100) through the injection punch (92), and applying pressure at a low speed to form a composite piston casting; S5: the upper die (6) and the extrusion punch (8) move further downward and compress the ring member (101) and the composite piston casting to deform; S6: The upper die (6) and the extrusion punch (8) move upward, and the injection punch (92) pushes the material handle (11), the flow guide (71) and the composite piston casting to move upward together and separate from the lower die (7); S7: Drill and mill the material handle (11), cut off the connection between the material handle (11) and the aluminum piston body (1) at the clamping ring (712), and then separate the aluminum piston body (1), the material handle (11) and the guide member (71).

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