Piston, piston assembly, engine and automobile

Abstract

The invention discloses a piston, a piston assembly, an engine and an automobile, and relates to the technical field of engines. The piston comprises a piston body and a heat insulation layer, the piston body is provided with a first side and a second side which are opposite, the second side is used for being connected with a piston connecting rod, and the first side corresponds to the bottom of the cylinder body; the heat insulation layer is arranged on the second side of the piston body. According to the technical scheme, the heat insulation layer is arranged on one side which is not in direct contact with the cylinder body, so that the heat insulation layer can be prevented from being in direct contact with fuel in the cylinder during use, high thermal stress and thermal shock caused by the fuel during combustion are reduced, the problems of cracking and stripping of the heat insulation layer can be reduced, the problems of insufficient combustion and local knocking can be reduced, and the service life of the cylinder is prolonged. The reliability and the service life of the piston can be improved. According to the piston provided by the technical scheme of the invention, a heat insulation layer material does not need to be modified, a special coating process is also not needed, and the problems that an existing piston preparation process is tedious, the production cost is high, and a heat insulation layer is prone to failure can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and in particular to a piston, a piston assembly, an engine and a car. Background Art

[0002] Hybrid vehicles are an important component of energy-saving vehicles. For internal combustion engines, there are different forms of energy losses, such as heat transfer loss, exhaust loss, pumping loss, friction loss, etc., which restrict their thermal efficiency. Therefore, it is necessary to study relevant measures to reduce energy loss to improve the thermal efficiency of internal combustion engines.

[0003] In an internal combustion engine, most of the heat generated by the combustion process will be transferred to the piston, cylinder head and cylinder liner, etc., and finally dissipated through the engine coolant. This direct heat loss to the combustion chamber wall reduces the power generated, thereby reducing the efficiency of the internal combustion engine. To solve this problem, in recent years, the technology of applying a thermal insulation layer on the piston surface has been widely used. The thermal insulation coating is usually made of ceramic materials, which can effectively insulate and reduce the operating temperature of the piston. Through the thermal insulation effect, the piston is protected from the direct effect of high-temperature combustion gas, thereby reducing mechanical damage and thermal fatigue caused by high temperature, improving engine performance and extending the service life of the piston. In addition, by applying a thermal insulation layer on the engine piston components, heat loss can be greatly reduced, and higher temperatures and pressures can be provided after combustion and throughout the expansion process. The higher pressure during the expansion process can increase work extraction and improve thermal efficiency, thereby achieving improved thermal efficiency of the internal combustion engine.

[0004] The problem caused by applying an insulating coating on the surface of the piston is that the thermal insulation layer is prone to cracking and failure when it is exposed to high heat and high pressure for a long time, resulting in reduced reliability and service life of the piston. In order to improve the service life and heat insulation effect of the thermal insulation layer, researchers have developed new high-strength materials or high-heat-resistant materials, increased the coating area or strictly controlled the coating process. The preparation process of these improved methods is cumbersome, the production cost is high, and the problem of thermal insulation layer failure is still prone to occur after long-term use. Therefore, improving the defects of the existing piston, such as cumbersome preparation process, high production cost, and easy failure of the thermal insulation layer, is still a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] The main purpose of the present invention is to provide a piston, a piston assembly, an engine and a car, aiming to solve the problems of complicated piston preparation process, high production cost and easy failure of the heat insulation layer.

[0006] To achieve the above object, the present invention provides a piston, comprising:

[0007] a piston body, the piston body having a first side and a second side opposite to each other, the second side being used to connect with the piston connecting rod, the first side being used to correspond to the bottom of the cylinder body; and,

[0008] A heat insulation layer is arranged on the second side of the piston body.

[0009] In one embodiment, a mounting groove is provided on the second side of the piston body, and the mounting groove is used for mounting one end of the piston rod;

[0010] The heat insulation layer is at least arranged at the bottom of the installation groove.

[0011] In one embodiment, the compressive strength of the piston body is not less than 200 MPa; and / or,

[0012] The heat insulation layer includes a metal bonding layer and a ceramic layer which are sequentially arranged on the second side of the piston body.

[0013] In one embodiment, the thickness of the metal bonding layer is 20 to 100 μm; and / or,

[0014] The thickness of the ceramic layer is 40-500 μm.

[0015] In one embodiment, the material of the metal bonding layer is MCrAlY, wherein M is at least one of Ni and Co; and / or,

[0016] The material of the ceramic layer includes at least one of yttria stabilized zirconia (YSZ), gadolinium zirconate (GdZr) and silica reinforced porous anodic aluminum (SiPRA).

[0017] In one embodiment, the thermal conductivity of the metal bonding layer is 10 to 50 W / mK; and / or,

[0018] The thermal conductivity of the ceramic layer is 0.8-1.2 W / mK.

[0019] In one embodiment, the porosity of the metal bonding layer is 1 to 5%; and / or,

[0020] The porosity of the ceramic layer is 55-70%; and / or,

[0021] The roughness of the metal bonding layer is 5 to 20 μm; and / or,

[0022] The roughness of the ceramic layer is 1-5 μm.

[0023] The present invention provides a piston assembly, which includes a piston and a piston connecting rod. The piston includes the piston described in the above technical solution.

[0024] The present invention provides an engine, the engine comprising a piston assembly, and the piston assembly comprises the piston assembly described above.

[0025] The present invention provides a car, the car comprises an engine, and the engine comprises the engine described above.

[0026] The beneficial effects of the technical solution of the present invention are as follows:

[0027] The technical solution of the present invention reduces the heat transfer loss of energy generated by combustion in the engine cylinder by setting a heat insulation layer and utilizing the heat insulation characteristics of the heat insulation layer, and can also increase the combustion temperature in the cylinder, thereby facilitating the full combustion of the fuel and improving the effective thermal efficiency of the entire engine. Compared with the conventional heat insulation layer, the technical solution of the present invention adjusts the coating position of the heat insulation layer, and sets the heat insulation layer on the side that is not directly in contact with the cylinder body, so that the heat insulation layer can be prevented from directly contacting the fuel in the cylinder during use, reducing the high thermal stress and thermal shock caused by the fuel during combustion, thereby reducing the cracking and peeling problems of the heat insulation layer, which is beneficial to improving the reliability and life of the piston; and, since the heat insulation layer is not in contact with the fuel, the possibility of fuel immersion in the heat insulation layer is reduced, and the fuel fluidity and uneven mixing problems caused by the high surface roughness of the ceramic layer are reduced, thereby reducing the problems of incomplete combustion and local detonation; in addition, since the heat insulation layer is not in contact with the fuel, the fuel cannot be carbonized on the surface of the heat insulation layer to form carbon deposits, and the problem of reduced function of the heat insulation layer caused by carbon deposits is also improved. Therefore, the piston provided by the technical solution of the present invention can effectively improve the reliability and service life of the piston, and is used to solve the problem of easy failure of the heat insulation layer in the piston. In addition, since the piston provided by the technical solution of the present invention reduces the failure of the thermal insulation layer material by adjusting the coating position of the thermal insulation layer, there is no need to modify the thermal insulation layer material, there is no need to adjust the thermal insulation layer structure, and there is no need for a special coating process. The preparation process is simple and low-cost. Therefore, it can be used to improve the problems of complicated existing piston preparation processes and high production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 A schematic structural diagram of an embodiment of a piston provided by the present invention;

[0030] Figure 2 A schematic structural diagram of a heat-insulating layer in an embodiment of a piston provided by the present invention.

[0031] Description of Figure Numbers:

[0032] 100. Piston; 1. Piston body; 11. Mounting groove; 2. Heat insulation layer; 21. Metal bonding layer; 22. Ceramic layer.

[0033] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0036] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] In an internal combustion engine, most of the heat generated by the combustion process is transferred to the piston, cylinder head, cylinder liner, etc., and is ultimately dissipated through the engine coolant. This direct heat loss to the combustion chamber wall reduces the power generated, thereby reducing the efficiency of the internal combustion engine. To solve this problem, in recent years, the technology of applying a thermal insulation layer on the piston surface has been widely used. The thermal insulation coating is usually made of ceramic materials, which can effectively insulate and reduce the operating temperature of the piston. Through the thermal insulation effect, the piston is protected from the direct effect of high-temperature combustion gas, thereby reducing mechanical damage and thermal fatigue caused by high temperature, improving engine performance and extending the service life of the piston. In addition, by applying a thermal insulation layer on the engine piston components, heat loss can be greatly reduced, and higher temperatures and pressures can be provided after combustion and throughout the expansion process. The higher pressure during the expansion process can increase work extraction and improve thermal efficiency, thereby achieving improved thermal efficiency and cycle life of the internal combustion engine. In addition, the thermal insulation layer with low thermal inertia can provide a fast surface temperature response, which will shorten the time of catalyst flameout, thereby reducing the emission of unburned hydrocarbons (UBHC) and carbon monoxide (CO) during cold start.

[0038] In order to achieve a better thermal insulation effect and increase the service life of the piston, conventional pistons usually set the thermal insulation layer on the surface where the piston head is in direct contact with the combustion chamber. However, if the thermal insulation layer is set in this way, the thermal insulation layer will directly contact the combustion gas, especially the detonation area in the combustion chamber, which will produce higher thermal stress and thermal shock, causing cracks in the thermal insulation coating, and ultimately causing the thermal insulation coating to peel off and fail, thereby affecting the effect of the thermal insulation coating, and also affecting the reliability and life of the piston. In order to improve the service life and thermal insulation effect of the thermal insulation layer, researchers have developed new high-strength materials or high-heat-resistant materials, increased the coating area or strictly controlled the coating process. However, the preparation process of these improved methods is cumbersome, the production cost is high, and the problem of thermal insulation layer failure is still prone to long-term use. However, the preparation process of these improved methods is cumbersome, the production cost is high, and the problem of thermal insulation layer failure is still prone to long-term use.

[0039] In addition, since most of the thermal insulation layer material is formed by the combination of thermal insulation material particles (powder) with gaps between the particles, the thermal insulation coating is usually porous. The porous structure may cause the following problems: First, the surface roughness of the thermal insulation coating is relatively high, which affects the flow and may cause uneven mixing of the combustible gas in the combustion chamber, causing local detonation. On the other hand, it will also cause a large amount of high-temperature gas to stay in the combustion chamber for too long, thereby increasing heat loss; second, in a direct injection engine, if the mist-sprayed fuel reaches the piston surface, the fuel will penetrate into the thermal insulation layer through the above-mentioned gap and cannot burn, resulting in incomplete combustion, thereby worsening the engine fuel consumption. On the other hand, if the immersed fuel gradually carbonizes and remains as carbon deposits, the thermal conductivity of the thermal insulation layer will increase, resulting in a decrease in function. Therefore, improving the defects of the complicated piston preparation process, high production cost, and easy failure of the thermal insulation layer is still a technical problem that technicians in the field need to solve urgently.

[0040] In view of this, the present invention provides a piston.

[0041] See also Figure 1 In one embodiment of the present invention, the piston 100 comprises:

[0042] A piston body 1, wherein the piston body 1 has a first side and a second side opposite to each other, wherein the second side is used to connect with the piston connecting rod, and the first side is used to correspond to the bottom of the cylinder body; and

[0043] The heat insulation layer 2 is arranged on the second side of the piston body 1 .

[0044] The technical solution of the present invention reduces the heat transfer loss of energy generated by combustion in the engine cylinder by setting the heat insulation layer 2, and also increases the combustion temperature in the cylinder, thereby facilitating the full combustion of the fuel and improving the effective thermal efficiency of the entire engine. On the other hand, since the technical solution of the present invention sets the heat insulation layer 2 on the side that is not directly in contact with the cylinder body, compared with the conventional heat insulation layer setting, the heat insulation layer 2 can be prevented from directly contacting the fuel in the cylinder during use, thereby reducing the high thermal stress and thermal shock caused by the fuel during combustion, thereby reducing the possibility of cracking and peeling of the heat insulation layer 2, which is beneficial to improving the reliability and life of the piston; and, since the heat insulation layer 2 is not in direct contact with the fuel, the possibility of fuel immersion in the heat insulation layer 2 is reduced, and the problems of poor fuel fluidity and uneven mixing caused by the high surface roughness of the ceramic layer are reduced, thereby reducing the problems of incomplete combustion and local detonation; in addition, since the heat insulation layer 2 is not in direct contact with the fuel, the fuel cannot be carbonized on the surface of the heat insulation layer 2 to form carbon deposits, thereby improving the problem of reduced function of the heat insulation layer 2 caused by carbon deposits. Therefore, the piston provided by the technical solution of the present application can not only reduce heat transfer losses, promote full combustion of fuel, and improve the effective thermal efficiency of the entire engine, but also effectively improve the reliability and service life of the piston, and can be used to solve the problem of easy failure of the thermal insulation layer in the piston.

[0045] The technical solution of the present invention reduces the failure of the thermal insulation layer 2 material by adjusting the coating position of the thermal insulation layer, thereby improving the effective thermal efficiency of the entire engine and the service life of the piston. It does not require complex modification of the thermal insulation layer material, does not require adjustment of the thermal insulation layer structure, and does not require a special coating process. The preparation process is simple and the preparation cost is low. It can be used to improve the problems of complicated existing piston preparation processes, high production costs, and easy failure of the thermal insulation layer.

[0046] See also Figure 1In the implementation of the present invention, a mounting groove 11 is provided on the second side of the piston body 1, and the mounting groove 11 is used for mounting one end of the piston rod; the thermal insulation layer 2 is at least provided at the bottom of the mounting groove 11. It should be noted that the thermal insulation layer 2 can be coated on the bottom of the mounting groove 11, or on the side of the mounting groove 11, or on the bottom and side of the mounting groove 11 at the same time. The coating area of ​​the thermal insulation layer 2 has a significant impact on its performance and function. Large-area coating can effectively enhance the thermal insulation performance, help to evenly distribute the thermal stress caused by temperature changes, thereby reducing local stress concentration and improving the stability and life of the thermal insulation coating; large-area coverage can also improve the overall mechanical strength of the substrate. However, if the thermal insulation layer 2 is too effective, it will also cause the temperature in the cylinder to be too high, reduce the charging efficiency, and there is a risk of knock for the spark ignition engine. In one embodiment of the present invention, the service life, thermal insulation effect and processability of the thermal insulation layer 2 are comprehensively considered, and the thermal insulation layer 2 is coated on the bottom of the mounting groove 11, so that the thermal insulation layer 2 has a better effect of reducing heat transfer, while ensuring that the temperature in the cylinder will not be too high, thereby reducing the risk of engine knock.

[0047] Furthermore, in order to improve the ability of the piston body 1 to resist high thermal stress, the compressive strength of the piston body 1 is set to be no less than 200 MPa. The compressive strength refers to the strength when the piston body 1 withstands an explosion pressure of 108 bar. The present invention does not limit the specific material of the piston body 1, and at least one of cast aluminum, cast iron, and forged steel can be selected.

[0048] See also Figure 2 In an embodiment of the present invention, the thermal insulation layer 2 includes a metal bonding layer 21 and a ceramic layer 22 which are sequentially arranged on the second side of the piston body 1. In the present invention, the thermal insulation layer 2 adopts a conventional double-layer thermal insulation layer structure, which is composed of a metal bonding layer 21 and a ceramic layer 22. The metal bonding layer 21 is used to relieve the stress caused by the mismatch of thermal expansion coefficients between the ceramic layer 22 and the piston body 1 material. The metal bonding layer 21 can also form a dense oxide film at high temperature, which can prevent the diffusion of oxygen elements into the interior of the piston body 1, thereby protecting the piston body 1 from further oxidation. The ceramic layer 22 is used to provide a thermal insulation effect, which can effectively reduce the transfer of heat to the piston body 1, thereby reducing the working temperature of the piston body 1.

[0049] In an embodiment of the present invention, the thickness of the metal bonding layer 21 is 20 to 100 μm. Selecting an appropriate thickness of the metal 21 bonding layer can improve the oxidation resistance of the coating, extend the service life, and maintain good bonding strength and wear resistance. The thickness of the bonding layer also plays an important role in matching the thermal expansion coefficient of the coating. An overly thick metal bonding layer may also cause more voids and microcracks to form inside the coating, reducing the overall performance of the metal bonding layer. When the thickness of the metal bonding layer 21 is set within the above range, the metal bonding layer 21 has better oxidation resistance, better bonding strength with the ceramic layer 22, and better stress relief effect on the mismatch of thermal expansion coefficients.

[0050] In an embodiment of the present invention, the thickness of the ceramic layer 22 is 40 to 500 μm. If the coating thickness of the ceramic layer 22 is too thin, the heat insulation effect is weak and the purpose of reducing heat transfer loss cannot be achieved; if the coating thickness is too thick, the cylinder temperature will be too high, the charging efficiency will be reduced, and there will be a risk of knocking for the spark ignition engine. Setting the thickness of the ceramic layer 22 within the above range is conducive to extending the service life of the internal combustion engine components and ensuring the reduction of heat transfer effect.

[0051] In an embodiment of the present invention, the material of the metal bonding layer 21 is MCrAlY, wherein M is at least one of Ni and Co, and Cr, Al, and Y refer to chromium, aluminum, and yttrium, respectively; the material of the ceramic layer 22 includes at least one of yttria-stabilized zirconia (YSZ), gadolinium zirconate (GdZr), and silica-reinforced porous anodic aluminum (SiPRA). The technical solution of the present invention does not limit the specific materials of the metal bonding layer 21 and the ceramic layer 22, and conventional metal bonding layer materials and ceramic layer materials can be used.

[0052] In an embodiment of the present invention, the thermal conductivity of the metal bonding layer 21 is 10 to 50 W / mK. Setting the thermal conductivity of the metal bonding layer 21 within the above range is conducive to blocking the heat from being transferred from the thermal barrier coating to the piston body 1, reducing heat transfer losses, and also reducing the stress between the ceramic layer 22 and the piston body 1 caused by temperature changes, relieving thermal stress and thermal deformation, thereby improving the durability and working stability of the piston.

[0053] In the embodiment of the present invention, the thermal conductivity of the ceramic layer 22 is 0.8 to 1.2 W / mK. Setting the thermal conductivity of the ceramic layer 22 within the above range is conducive to reducing the heat conduction between the ceramic layer 22 and the piston body 1, reducing the heat transfer loss between the high-temperature combustion gas and the piston wall during the engine combustion process, improving the engine efficiency, and preventing the piston from overheating.

[0054] In an embodiment of the present invention, the porosity of the metal bonding layer 21 is 1-5%. The number of pores in the metal bonding layer 21 will affect the durability of the thermal insulation coating and the effect of relieving internal stress. Setting the porosity of the metal bonding layer 21 to 1-5% is conducive to improving the overall reliability of the metal bonding layer 21.

[0055] In an embodiment of the present invention, the porosity of the ceramic layer 22 is 55-70%. An appropriate amount of pores can significantly reduce the thermal conductivity and volume specific heat of the coating, thereby reducing the reduction in thermal efficiency of the engine due to heat loss. Setting the porosity of the metal bonding layer 21 to 55-70% is beneficial to reducing heat transfer on the wall of the piston.

[0056] In the embodiment of the present invention, the roughness of the metal bonding layer 21 is 5-20 μm. Setting the roughness of the metal bonding layer 21 within the above range can ensure good bonding between the metal bonding layer 21 and the ceramic layer 22, and maintain stability and durability in a high temperature environment.

[0057] In an embodiment of the present invention, the roughness of the ceramic layer 22 is 1 to 5 μm. The roughness not only affects the bonding strength, the stress distribution and fracture behavior inside the coating, but also affects the uniformity and stability of the ceramic layer 22, and further affects the high-temperature oxidation resistance of the coating. Setting the roughness of the ceramic layer 22 within the above range is conducive to obtaining a ceramic layer 22 with good mechanical strength, uniformity, stability and high-temperature oxidation resistance.

[0058] The present invention provides a method for preparing a piston, please refer to Figure 1 and Figure 2 , the preparation method of the piston comprises the following steps:

[0059] A piston body 1 is provided;

[0060] A metal bonding layer 21 is coated on the mounting groove 11 of the piston body 1;

[0061] The ceramic layer 22 is coated on the surface of the metal bonding layer 21 to obtain the piston 100 .

[0062] In the embodiment of the present invention, conventional methods for preparing the heat insulating layer can be used. The metal bonding layer 21 can be prepared by plasma spraying, and the ceramic layer 22 can be prepared by plasma spraying or anodizing. When preparing the metal bonding layer 21, MCrAlY alloy powder is deposited on the surface to be sprayed of the piston body 1 to form the metal bonding layer 21; when preparing the ceramic layer 22, yttria-stabilized zirconia (YSZ) is made by plasma spraying or a porous anodized aluminum coating is formed by an anodizing process, and a layer of formaldehyde silane sealing agent is coated on the surface of the anodized film to infiltrate into the pores and convert into SiO2.

[0063] Compared with the conventional piston preparation method, the technical solution of the present invention adjusts the coating position of the heat insulation layer 2, and sets the heat insulation layer 2 on the side that is not directly in contact with the cylinder body. The piston preparation method provided by the present invention does not require complex modification of the heat insulation layer material, does not require adjustment of the heat insulation layer structure, and does not require a special coating process. The preparation process is simple and low in cost, and can be used to improve the problems of the existing piston, such as complicated preparation process, high production cost, and easy failure of the heat insulation layer.

[0064] The present invention provides a piston assembly, which includes the piston and piston connecting rod described in the above technical solution. The piston assembly includes all technical solutions of the piston, and thus has all the beneficial effects of the piston, which will not be described in detail in the present invention.

[0065] The present invention provides an engine, the engine comprising the piston assembly described in the above technical solution. The engine comprises all technical solutions of the piston assembly, and thus has all the beneficial effects of the piston assembly, which will not be described in detail in the present invention.

[0066] The present invention provides a car, the car includes the engine described in the above technical solution. The car includes all technical solutions of the engine, and thus has all the beneficial effects of the engine, which will not be described in detail in the present invention.

[0067] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A piston, characterized in that: include: A piston body, the piston body having a first side and a second side opposite to each other, the second side being used to connect with the piston connecting rod, and the first side being used to correspond to the bottom of the cylinder body; as well as, A heat insulation layer is arranged on the second side of the piston body.

2. The piston according to claim 1, characterized in that The second side of the piston body is provided with a mounting groove, and the mounting groove is used for mounting one end of the piston rod; The heat insulation layer is at least arranged at the bottom of the installation groove.

3. The piston according to claim 1 or 2, characterized in that: The compressive strength of the piston body is not less than 200 MPa; and / or, The heat insulation layer includes a metal bonding layer and a ceramic layer which are sequentially arranged on the second side of the piston body.

4. The piston according to claim 3, characterized in that The thickness of the metal bonding layer is 20 to 100 μm; and / or, The thickness of the ceramic layer is 40-500 μm.

5. The piston according to claim 3, characterized in that The material of the metal bonding layer is MCrAlY, wherein M is at least one of Ni and Co; and / or, The material of the ceramic layer includes at least one of yttria-stabilized zirconia, gadolinium zirconate and silica-reinforced porous anodic aluminum oxide.

6. The piston according to claim 3, characterized in that The thermal conductivity of the metal bonding layer is 10 to 50 W / mK; and / or, The thermal conductivity of the ceramic layer is 0.8-1.2 W / mK.

7. The piston according to claim 3, characterized in that The porosity of the metal bonding layer is 1 to 5%; and / or, The porosity of the ceramic layer is 55-70%; and / or, The roughness of the metal bonding layer is 5 to 20 μm; and / or, The roughness of the ceramic layer is 1-5 μm.

8. A piston assembly, characterized in that: The piston assembly comprises a piston and a piston connecting rod, and the piston comprises the piston according to any one of claims 1 to 7.

9. An engine, characterized in that: The engine includes a piston assembly, and the piston assembly includes the piston assembly of claim 8.

10. An automobile, characterized in that: The automobile includes an engine, and the engine includes the engine of claim 9.

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