Valve guide pipe

Abstract

The utility model belongs to the technical field of engine post-processing, and particularly relates to a valve guide pipe. The valve guide pipe comprises a body and a heat insulation coating, the body comprises a first end, the first end is the end, located in a cylinder cover, of the body, the first end is coated with the heat insulation coating, the temperature of the valve guide pipe is reduced by additionally arranging the heat insulation coating to reduce heat transfer between the body and the outside, and therefore the abrasion resistance of the valve guide pipe is improved, and heat fatigue damage is reduced; the heat insulation coating is a surface treatment technology, has low heat conductivity, has a heat resistance effect and can effectively block or reflect heat, so that the internal temperature of an object is reduced, the heat preservation or heat insulation effect is achieved, the temperature of the valve guide pipe can be remarkably reduced, and the service life of the valve guide pipe is prolonged. Therefore, thermal fatigue damage and abrasion to the surface of the first end caused by high heat are reduced.

Description

Technical Field

[0001] This utility model belongs to the field of engine aftertreatment technology, and specifically relates to a valve guide. Background Technology

[0002] This section provides only background information relevant to this disclosure and is not necessarily prior art.

[0003] With the development of the automotive industry, the requirements for engine performance are increasing. As an important component of the engine, the performance of the valve guide directly affects the engine's efficiency and lifespan.

[0004] Currently, valve guides are made entirely of high-temperature resistant powder metallurgy. In high-temperature environments, they are prone to thermal fatigue damage and wear, affecting the long-term stable operation of the engine. Utility Model Content

[0005] This utility model aims to at least partially solve one of the technical problems in the related art.

[0006] This utility model provides a valve guide for installation inside the cylinder head, comprising:

[0007] The body includes a first end, which is the end of the body located inside the cylinder head; and

[0008] A heat-insulating coating is applied to the first end.

[0009] This valve guide lowers its temperature by adding a heat-insulating coating to reduce heat transfer between the valve body and the outside, thereby improving its wear resistance, reducing thermal fatigue damage, and extending its service life.

[0010] Thermal insulation coating is a material coating used to reduce heat transfer. Thermal insulation coating has a low thermal conductivity. Because thermal insulation coating has a thermal resistance effect, it can effectively block or reflect heat, thereby reducing the internal temperature of the object and achieving the effect of heat preservation or insulation. It can significantly reduce the temperature of the valve guide, thereby reducing thermal fatigue damage and wear caused by high heat to the first end surface.

[0011] In some embodiments, the heat-insulating coating is applied to the outer side of the first end.

[0012] The heat insulation coating does not coat the inner diameter of the first end, thereby reducing the area to be surface treated and reducing processing and material costs.

[0013] In some embodiments, the sum of the diameter of the outer periphery of the first end and the thickness of the heat insulation coating is a first parameter, and the diameter of the connection between the body and the first end is a second parameter, wherein the first parameter and the second parameter are the same.

[0014] The valve guide structure ensures that the diameter of the first end after surface treatment is consistent with that of the body, avoiding the increase in diameter caused by the heat insulation coating at the first end, thus guaranteeing the performance of the valve guide.

[0015] In some embodiments, the thickness of the heat-insulating coating is 0.35mm-0.65mm.

[0016] This thin coating provides effective thermal barrier insulation without the material waste associated with excessive thickness, and it also improves coating stability, preventing peeling. This thickness range contributes to weight reduction; compared to thicker coatings (e.g., 1 mm or more), a 0.35 mm-0.65 mm thermal insulation coating can reduce weight by 30%-50%, thus lowering the engine's thrust-to-weight ratio. Furthermore, this thickness range allows for better adaptation to the confined space of the valve guides, preventing blockage.

[0017] In some embodiments, the heat-insulating coating includes a heat-insulating layer, the material of which is a ceramic material.

[0018] Ceramic materials possess excellent high-temperature resistance, low thermal conductivity, low density, high hardness, and high wear resistance. Specifically, ceramic materials typically have melting points exceeding 2000℃, maintaining structural stability at high temperatures for extended periods. They are not easily degraded in oxidizing atmospheres, protecting the substrate material from oxidative corrosion and exhibiting high resistance to high-temperature oxidation. The low thermal conductivity of ceramic materials significantly reduces heat transfer to the substrate, improving equipment thermal efficiency. Furthermore, by adjusting the composition, the coefficient of thermal expansion of ceramic materials can approach that of a metal substrate, reducing the risk of spalling under thermal cycling and extending coating life. Ceramic materials demonstrate stability in acidic, alkaline, or salt spray environments. The coating hardness of ceramic materials can reach HV 1000-1500, reducing wear and increasing lifespan by 3-5 times.

[0019] In some embodiments, the material of the heat insulation layer is zirconium oxide stabilized yttrium oxide.

[0020] Yttrium-stabilized zirconia, as a thermal insulation layer, offers both thermal insulation and corrosion resistance. Its thermal conductivity is only 1.2-2.5 W / (m·K) (from room temperature to 1200℃), significantly lower than that of metallic substrates (such as nickel-based alloys, which have a thermal conductivity of approximately 20 W / (m·K)), effectively preventing high-temperature transfer to the substrate. In this insulation material, the doping of yttrium oxide maintains a stable cubic phase structure at high temperatures (up to approximately 1200℃), preventing volume expansion and coating cracking caused by the transformation from monoclinic to tetragonal phases. Even during long-term high-temperature service, yttrium-stabilized zirconia maintains a porous or columnar crystal structure, delaying densification and maintaining low thermal conductivity, which is beneficial for ensuring high phase stability and resistance to sintering.

[0021] In some embodiments, the thickness of the insulation layer is 0.2mm-0.55mm.

[0022] This thin insulation layer provides effective thermal barrier insulation without the material waste associated with excessively thick coatings, and it also improves coating stability, preventing peeling. Furthermore, this thickness range contributes to weight reduction; compared to thicker coatings (e.g., 1 mm or more), a 0.2 mm-0.55 mm insulation layer reduces engine thrust-to-weight ratio loss. Additionally, this thickness range allows for better adaptation to the confined space of the valve guides, preventing blockage.

[0023] In some embodiments, the heat-insulating coating further includes:

[0024] An adhesive layer is located between the thermal insulation layer and the first end.

[0025] Due to the significant difference in thermal expansion coefficients between ceramic materials and metal substrates, direct contact can lead to interfacial stress accumulation during thermal cycling, causing coating peeling. The adhesive layer, with its thermal expansion coefficient falling between that of the first end and the ceramic insulation layer, reduces interfacial stress. The adhesive layer also exhibits some plasticity at high temperatures, absorbing some thermal stress. Simultaneously, the roughened surface of the adhesive layer increases the mechanical bonding area between the ceramic insulation layer and the adhesive layer. Furthermore, during high-temperature service, localized reactions may occur at the interface between the adhesive layer and the ceramic insulation layer, forming chemical bonds and enhancing interfacial adhesion.

[0026] In some embodiments, the adhesive layer is made of NiCrAlY.

[0027] NiCrAlY acts as a binder layer. Aluminum (Al) preferentially oxidizes in high-temperature oxidizing environments, forming a dense, continuous alumina layer. This layer exhibits an extremely low oxygen diffusion rate, effectively blocking oxygen diffusion into the substrate and preventing high-temperature oxidation of the base metal. Chromium (Cr) oxidizes to form chromium oxide, which forms a stable protective film in corrosive media containing sulfur and chlorine, inhibiting sulfide and chlorination corrosion of the substrate. Yttrium (Y) accumulates at the alumina grain boundaries, inhibiting grain coarsening and preventing cracking and peeling of the insulation layer.

[0028] In some embodiments, the thickness of the adhesive layer is 0.1 mm to 0.2 mm.

[0029] In high-temperature coating systems, the adhesive layer thickness is designed within the range of 0.1-0.2 mm. By balancing stress relief, improving oxidation resistance, and reducing process costs, the adhesive layer can fully absorb interfacial stress caused by differences in thermal expansion coefficients. If the adhesive layer is too thin (<0.1 mm), the stress buffer is insufficient, which can easily lead to premature peeling of the ceramic layer. If the adhesive layer is too thick (>0.2 mm), the difference in CTE between the adhesive layer and the substrate may introduce additional residual stress.

[0030] A bonding layer thickness of 0.1mm-0.2mm is beneficial for enhancing anti-stripping ability, inhibiting element interdiffusion, avoiding the formation of brittle phases, balancing the thermal conductivity and insulation efficiency of the coating system, and improving corrosion and erosion resistance. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the valve guide provided in an embodiment of the present invention.

[0033] The markings in the image are as follows:

[0034] 100. Main body; 110. First end;

[0035] 200. Heat insulation coating. Detailed Implementation

[0036] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0037] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0038] This embodiment provides a valve guide. The valve guide is a key component in an engine, primarily used to guide the reciprocating motion of the valve and ensure the sealing performance between the valve stem and valve seat. The valve guide is at least partially installed within the cylinder head, and its internal structure contacts the valve stem through a precision fit to ensure that the valve moves in a straight line during opening and closing, reducing wear and maintaining good sealing. Furthermore, the valve guide also plays a role in transferring heat from the valve stem to the cylinder head, thereby contributing to the overall thermal management of the engine.

[0039] Currently, commonly used valve guides are made entirely of powder metallurgy. These valve guides are prone to thermal fatigue damage and wear under the high-temperature environment inside the engine, affecting the long-term stable operation of the engine. In particular, the end of the valve guide located inside the cylinder head shows signs of high-temperature oxidation and accumulates a large amount of carbon deposits.

[0040] To address the aforementioned issues, in this embodiment, the valve guide includes a body 100 and a heat-insulating coating 200. The body 100 includes a first end 110, which is the end of the body 100 located inside the cylinder head; the heat-insulating coating 200 is applied to the first end 110.

[0041] The valve guide lowers its temperature by adding a heat-insulating coating 200 to reduce heat transfer between the body 100 and the outside, thereby improving its wear resistance, reducing thermal fatigue damage, and extending its service life.

[0042] The heat insulation coating 200 is a surface treatment technology. The heat insulation coating 200 has a low thermal conductivity. Because the heat insulation coating 200 has a thermal resistance effect, it can effectively block or reflect heat, thereby reducing the internal temperature of the object and achieving the effect of heat preservation or insulation. It can significantly reduce the temperature of the valve guide, thereby reducing the thermal fatigue damage and wear caused by high heat to the surface of the first end 110.

[0043] Specifically, the first end 110 of the valve guide experiences oxidation and oil coking at high temperatures. Oxides and coked oil adhere to the inner wall of the valve guide and the valve stem. During operation, friction between the valve stem and the valve guide causes the oxides and coked oil to peel off. This process repeats itself during valve guide operation, ultimately leading to valve guide wear. Therefore, high temperature is a significant cause of valve guide wear. In this embodiment, the wear resistance of the valve guide is effectively addressed by incorporating a heat-insulating coating 200.

[0044] The body 100 is made of powder metallurgy material to ensure the basic strength and stability of the valve guide.

[0045] In some embodiments, the heat insulation coating 200 is applied to the outer side of the first end 110, but not to the inner diameter of the first end 110, thereby reducing the area to be surface treated and reducing processing and material costs.

[0046] The sum of the diameter of the outer periphery of the first end 110 and the thickness of the heat insulation coating 200 is the first parameter, and the diameter of the connection between the body 100 and the first end 110 is the second parameter. The first parameter and the second parameter are the same, so that the diameter of the first end 110 after surface treatment is consistent with that of the body 100, avoiding the increase in diameter caused by the heat insulation coating 200 of the first end 110, thus ensuring the performance of the valve guide.

[0047] Specifically, during the processing of the body 100, the thickness of the heat insulation coating 200 is removed based on the design dimensions of the first end 110, so that the diameter of the outer periphery of the first end 110 after surface treatment is consistent with that of the body 100.

[0048] In some embodiments, the thickness of the heat-insulating coating 200 is 0.35mm-0.65mm. This thin thickness provides a thermal barrier effect, avoids material waste caused by excessive coating thickness, and improves coating stability, preventing peeling.

[0049] Meanwhile, this thickness range is beneficial for improving weight reduction. Compared to thicker coatings (such as 1 mm or more), a 0.35 mm-0.65 mm heat insulation coating thickness of 200 mm can reduce weight by 30%-50%, thus reducing engine thrust-to-weight ratio loss. In addition, this 200 mm thickness range of the heat insulation coating is beneficial for adapting to the narrow space of the valve guide, avoiding blockage of the valve guide passage.

[0050] Specifically, the thickness of the heat insulation coating 200 can be 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, or 0.65mm.

[0051] The thickness of the heat insulation coating 200 is preferably 0.5 mm. This thickness is beneficial to further enhance the performance of the heat insulation coating 200, and has the effect of optimizing thermal protection performance, improving mechanical properties and durability.

[0052] A 0.5mm thick heat insulation coating 200 helps control costs and reduces residual stress caused by an excessively thick heat insulation coating 200, thereby improving the yield rate.

[0053] Specifically, the heat insulation coating 200 can effectively block the direct thermal impact of high-temperature gas or exhaust gas on the basic material of the body 100, and prevent the material of the body 100 from overheating and deforming.

[0054] Furthermore, the heat-insulating coating 200 is processed by plasma spraying, an advanced material surface treatment technology. This plasma spraying technology uses a plasma arc as a heat source to heat materials (such as ceramics, alloys, metals, etc.) to a molten or semi-molten state, and then sprays them at high speed onto the pre-treated workpiece surface, namely the outer surface of the first end 110, thereby forming a coating with specific properties.

[0055] The heat insulation coating 200 includes a heat insulation layer, the material of which is ceramic.

[0056] In summary, ceramic materials possess excellent high-temperature resistance, low thermal conductivity, low density, high hardness, and high wear resistance. Specifically, ceramic materials typically have melting points exceeding 2000℃, maintaining structural stability at high temperatures for extended periods. They are not easily degraded in oxidizing atmospheres, protecting the substrate material from oxidative corrosion and exhibiting high resistance to high-temperature oxidation. The low thermal conductivity of ceramics significantly reduces heat transfer to the substrate, improving equipment thermal efficiency. Furthermore, by adjusting the composition, the coefficient of thermal expansion of ceramic materials can approach that of a metal substrate, reducing the risk of spalling under thermal cycling and extending coating life. Ceramic materials demonstrate stability in acidic, alkaline, or salt spray environments. The coating hardness of ceramic materials can reach HV 1000-1500, reducing wear and increasing lifespan by 3-5 times.

[0057] In some embodiments, the material of the heat insulation layer is zirconium oxide stabilized yttrium oxide.

[0058] Zirconia-stabilized yttrium oxide is an important high-temperature material, mainly used in thermal barrier coatings, solid oxide fuel cells, sensors, and other fields. Zirconia-stabilized yttrium oxide is prepared by adding a certain proportion of yttrium oxide to zirconia to improve its thermal stability and mechanical properties.

[0059] Yttrium-stabilized zirconia, as a thermal insulation layer, offers both thermal insulation and corrosion resistance. Its thermal conductivity is only 1.2-2.5 W / (m·K) (from room temperature to 1200℃), significantly lower than that of metallic substrates (such as nickel-based alloys, which have a thermal conductivity of approximately 20 W / (m·K)), effectively preventing high-temperature transfer to the substrate. In this insulation material, the doping of yttrium oxide maintains a stable cubic phase structure at high temperatures (up to approximately 1200℃), preventing volume expansion and coating cracking caused by the transformation from monoclinic to tetragonal phases. Even during long-term high-temperature service, yttrium-stabilized zirconia maintains a porous or columnar crystal structure, delaying densification and maintaining low thermal conductivity, which is beneficial for ensuring high phase stability and resistance to sintering.

[0060] Yttrium-stabilized zirconia is stable in high-temperature oxidizing and sulfur-containing environments, protecting the first 110 end from oxidation corrosion. Yttrium-stabilized zirconia has a hardness of 12-14 GPa and, due to the phase transformation toughening effect, possesses a certain degree of fracture toughness, which is beneficial for resisting sand erosion and fretting wear.

[0061] In some embodiments, the thickness of the insulation layer is 0.2mm-0.55mm.

[0062] This thin heat insulation layer achieves a thermal barrier effect without the material waste caused by excessive coating thickness, and also improves coating stability, preventing peeling. Simultaneously, this thickness range contributes to weight reduction; compared to thicker coatings (e.g., 1 mm or more), a heat insulation layer thickness of 0.2 mm to 0.55 mm reduces engine thrust-to-weight ratio loss. Furthermore, the 200 mm thickness range of this heat insulation coating helps adapt to the confined space of the valve guides, preventing blockage of the valve guide passages.

[0063] Specifically, the thickness of the heat insulation coating 200 can be 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or 0.55mm.

[0064] The thickness of the heat insulation coating 200 is preferably 0.3mm-0.4mm. This thickness is beneficial to further enhance the performance of the heat insulation coating 200, and has the effect of optimizing thermal protection performance, improving mechanical properties and durability.

[0065] A 0.3mm-0.4mm thick insulation layer helps control costs and reduces residual stress caused by excessively thick insulation layers, thereby improving yield.

[0066] In some embodiments, the heat insulation coating 200 further includes an adhesive layer located between the heat insulation layer and the first end 110.

[0067] Due to the significant difference in thermal expansion coefficients between ceramic materials and metal substrates, direct contact can lead to interfacial stress accumulation during thermal cycling, causing coating peeling. The adhesive layer, with its thermal expansion coefficient falling between that of the first end (110) and the ceramic insulation layer, reduces interfacial stress. The adhesive layer also exhibits some plasticity at high temperatures, absorbing some thermal stress. Simultaneously, the roughened surface of the adhesive layer increases the mechanical bonding area between the ceramic insulation layer and the adhesive layer. Furthermore, during high-temperature service, localized reactions may occur at the interface between the adhesive layer and the ceramic insulation layer, forming chemical bonds and enhancing interfacial adhesion.

[0068] In some embodiments, the adhesive layer is made of NiCrAlY.

[0069] NiCrAlY acts as a binder layer. Aluminum (Al) preferentially oxidizes in high-temperature oxidizing environments, forming a dense, continuous alumina layer. This layer exhibits an extremely low oxygen diffusion rate, effectively blocking oxygen diffusion into the substrate and preventing high-temperature oxidation of the base metal. Chromium (Cr) oxidizes to form chromium oxide, which forms a stable protective film in corrosive media containing sulfur and chlorine, inhibiting sulfide and chlorination corrosion of the substrate. Yttrium (Y) accumulates at the alumina grain boundaries, inhibiting grain coarsening and preventing cracking and peeling of the insulation layer.

[0070] The coefficient of thermal expansion of NiCrAlY is approximately 12-13 × 10⁻⁶. -6 / K, situated between the metal substrate and the ceramic insulation layer, significantly reduces interfacial stress during thermal cycling. During engine start-stop (temperature fluctuations of 500-1100℃), the NiCrAlY bonding layer can reduce the interfacial thermal stress of the ceramic coating by 40%-60%, preventing peeling failure caused by direct contact between the ceramic layer and the substrate.

[0071] The Ni matrix maintains high strength and toughness at high temperatures (800-1100℃), absorbing thermal stress through plastic deformation and inhibiting crack propagation. The NiCrAlY layer acts as a physical barrier, preventing Ni and Co elements in the matrix from interdiffusion with some elements in the insulating layer of the ceramic material, thus avoiding the formation of brittle intermetallic compounds at the interface, which can lead to a decrease in bonding strength of more than 50%.

[0072] In some embodiments, the thickness of the adhesive layer is 0.1 mm to 0.2 mm.

[0073] In high-temperature coating systems, the adhesive layer thickness is designed within the range of 0.1-0.2 mm. By balancing stress relief, oxidation resistance, and process cost, the adhesive layer can effectively absorb interfacial stress caused by differences in the coefficients of thermal expansion. If the adhesive layer is too thin (<0.1 mm), the stress buffer is insufficient, which can easily lead to premature peeling of the ceramic layer. If the adhesive layer is too thick (>0.2 mm), the difference in CTE between the adhesive layer and the substrate may introduce additional residual stress.

[0074] A bonding layer thickness of 0.1mm-0.2mm is beneficial for enhancing anti-stripping ability, inhibiting element interdiffusion, avoiding the formation of brittle phases, balancing the thermal conductivity and insulation efficiency of the coating system, and improving corrosion and erosion resistance.

[0075] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0076] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0077] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0078] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0079] In this utility model, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0080] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A valve guide for mounting in a cylinder head, characterized by include: The body includes a first end, which is the end of the body located inside the cylinder head; as well as A heat-insulating coating is applied to the first end.

2. The valve guide of claim 1, wherein The heat-insulating coating is applied to the outer side of the first end.

3. The valve guide of claim 1, wherein The sum of the diameter of the outer periphery of the first end and the thickness of the heat insulation coating is the first parameter, and the diameter of the connection between the body and the first end is the second parameter. The first parameter and the second parameter are the same.

4. The valve guide according to any one of claims 1 to 3, characterized in that The thickness of the heat insulation coating is 0.35mm-0.65mm.

5. The valve guide of any one of claims 1-3, wherein, The heat insulation coating includes a heat insulation layer, and the material of the heat insulation layer is a ceramic material.

6. The valve guide of claim 5, wherein, The material of the heat insulation layer is zirconium oxide stabilized yttrium oxide.

7. The valve guide of claim 5, wherein, The thickness of the insulation layer is 0.2mm-0.55mm.

8. The valve guide of claim 5, wherein, The heat-insulating coating also includes: An adhesive layer is located between the thermal insulation layer and the first end.

9. The valve guide of claim 8, wherein, The adhesive layer is made of NiCrAlY.

10. The valve guide according to claim 8 or 9, characterized in that The thickness of the adhesive layer is 0.1mm-0.2mm.

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