A cylinder head exhaust side heat insulation and cooling structure, cylinder head and internal combustion engine

Abstract

This invention discloses a cylinder head exhaust-side heat insulation and cooling structure, a cylinder head, and an internal combustion engine. The cylinder head exhaust-side cooling structure involves adding a heat insulation and cooling channel to the cylinder head casting. This channel is located between the lower end face of the cylinder head and the exhaust port of the cylinder head, and the channel and the exhaust port are spatially intersecting each other. The channel can be used for the flow of cooling medium. By arranging the main body of the channel between the lower end face of the cylinder head and the exhaust port, and allowing it to pass through this area, heat is insulated from being conducted from high-temperature areas such as the exhaust port to the lower mounting surface of the cylinder head. At the same time, the internal cooling medium flows directly through the area where the heat is most concentrated. Under the dual effects of heat insulation and cooling, the operating temperature of this area can be reduced to below the aging temperature of the cylinder head material, thereby avoiding material annealing and hardness reduction, and fundamentally preventing blow-by problems caused by plastic deformation due to excessive heat load. This invention has a compact structure, significant cooling effect, and can be widely used in internal combustion engine cylinder heads.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, specifically to a cylinder head exhaust side heat insulation and cooling structure, a cylinder head, and an internal combustion engine. Background Technology

[0002] The internal combustion engine is the core component of a motorcycle. Because the cylinder head integrates core functions such as sealing and combustion, controlling intake and exhaust, and heat dissipation and airflow, its design directly affects the engine's lifespan, combustion efficiency, power output, fuel economy, and emissions. The cylinder head is tightly fixed above the cylinder block, forming the combustion chamber. During engine operation, the combustion and explosion of fuel generate power accompanied by extremely high temperatures and pressures, thus requiring extremely high levels of heat dissipation and sealing. However, after prolonged operation, the cylinder head of an internal combustion engine is prone to blow-by, severely impacting its lifespan. (See also...) Figure 1 - Figure 4 This is the exhaust side structure of the cylinder head of the existing internal combustion engine model Y10. Figure 1 and Figure 2 In the cylinder head 1, the blue lines represent the original combustion chamber cooling oil passage 6. It can be seen that the original cooling passage 6 extends away from the lower end face 7 of the cylinder head and cannot cool the lower end face of the cylinder head. Figure 3 The area within the red box is the discolored area on the lower end face of the cylinder head. After a 20,000km road test, analysis of the internal combustion engine revealed cylinder head blow-by, with noticeable discoloration on the exhaust side of the cylinder head and varying degrees of blow-by. Figure 4 The flatness inspection of the lower end face of the cylinder head exhaust side revealed that it exceeded the allowable limit of 0.1mm, reaching 0.14mm and showing a continuing tendency to increase. Analysis indicated that the large deformation of the cylinder head was a factor leading to combustion chamber seal failure, resulting in significant discoloration of the cylinder head. After systematically investigating and eliminating possible factors such as loose cylinder head nuts and failed gaskets, temperature and hardness tests were conducted on this area. The test results showed that the area with severely excessive flatness exhibited a significant decrease in hardness, and the engine operating temperature reached over 300℃; while the temperature of the corresponding area on the intake side of the lower end face of the cylinder head was below 200℃. Given that the aging temperature of cylinder head materials is known to be between 230℃ and 250℃, comprehensive analysis indicates that the excessively high temperature in the lower exhaust side region caused annealing of the cylinder head material, resulting in decreased hardness and plastic deformation under engine combustion pressure and other loads. When the deformation of the lower end face of the exhaust side of the cylinder head exceeds the compensation capacity of the cylinder gasket, blow-by will occur, leading to damage to the internal combustion engine or even engine seizure, which seriously endangers the health and safety of riders.

[0003] As is well known, adding an oil chamber inside the cylinder head to utilize coolant circulation to remove heat and solve high-temperature problems is theoretically feasible, but in engineering practice, it faces severe challenges in multiple dimensions, including fluid control, thermal management, structural strength, manufacturing processes, and system integration. One major challenge is fluid control and oil balance. The total amount of engine oil and the oil pump's supply capacity are fixed. The amount of oil diverted from the cylinder block to the cylinder head directly affects the lubrication of core components such as the crankshaft and connecting rods. If the oil inlet of the cylinder head's oil chamber is too large, a large amount of oil will flood into the cylinder head, causing the crankcase oil level to drop, resulting in insufficient lubrication and bearing failure. Simultaneously, excessive oil in the cylinder head increases crankcase pressure, leading to problems such as oil burning and piston ring blow-by. Secondly, adding an oil cavity to the cylinder head casting will inevitably thin the wall thickness, especially near high-temperature areas such as valve seats and spark plugs, which will form new stress concentration points. Under long-term alternating loads, fatigue cracks may occur, which will inevitably weaken its original structural strength. Meanwhile, the cylinder head itself bears huge explosive pressure and thermal stress.

[0004] Therefore, how to solve the problem of gas leakage in the cylinder head of an internal combustion engine after long-term operation, which seriously affects its service life, is a problem that is difficult for those skilled in the art to solve. It has long been neglected and has not been solved or broken through. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a cylinder head exhaust side cooling structure and a cylinder head. The technical problem to be solved is: how to achieve fluid control and oil balance, reduce the thermal load on the exhaust side to improve the hardness decay of the cylinder head, and increase the impact deformation resistance of the exhaust side, thereby avoiding excessive deformation of the cylinder head exhaust side leading to blow-by and seriously affecting its service life.

[0006] Furthermore, the present invention provides the exhaust-side cooling structure of the cylinder head and its application in internal combustion engines and motorcycles.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A heat insulation and cooling structure for the exhaust side of a cylinder head is provided by adding a heat insulation and cooling channel to the cylinder head casting. The heat insulation and cooling channel is located between the lower end face of the cylinder head and the exhaust passage of the cylinder head. The heat insulation and cooling channel and the exhaust passage of the cylinder head are spatially intersected, and the cooling channel is used for the flow of cooling medium.

[0009] As an optimization, the main body of the heat-insulating cooling channel passes through the area between the lower end face of the cylinder head and the exhaust port; the heat-insulating cooling channel has at least one oil inlet and at least one oil outlet, the oil inlet being used to communicate with the oil supply system and the oil outlet being used to communicate with the return system.

[0010] As an optimization, the oil inlet is located on the lower end face of the cylinder head and is connected to the engine oil supply system; the oil outlet is located on the side wall of the chain cavity of the cylinder head and is connected to the return system.

[0011] As an optimization, the heat insulation cooling channel is set independently, the oil inlet is located on the lower end face of the cylinder head, and the oil outlet is located on the chain cavity side wall, the lower end face of the cylinder head, or the outer wall of the cylinder head. An independent external pipeline is connected to the oil outlet, and the other end of the external pipeline is connected to the return system.

[0012] As an optimization, the main body section of the heat-insulating cooling channel has a flat cross-section, and its width is greater than its height; the ratio of the width W to the height H of the main body section of the cooling channel satisfies: W / H≥2.

[0013] As an optimization, the distance between the main body of the heat insulation cooling channel and the lower end face of the cylinder head is no more than 10mm, and the distance between it and the exhaust channel is no more than 10mm.

[0014] As an optimization, the distance between the outer end of the main body section of the heat insulation cooling channel and the outer wall of the cylinder head exhaust side is no more than 10mm.

[0015] As an optimization, the minimum wall thickness between the main body of the heat insulation cooling channel and the lower end face of the cylinder head, the minimum wall thickness between the channel and the exhaust channel, and the minimum wall thickness between the channel and the outer wall of the cylinder head exhaust side are all not less than 3mm.

[0016] A cylinder head with deformation resistance includes the aforementioned cylinder head exhaust side heat insulation and cooling structure.

[0017] An internal combustion engine, including the cylinder head as described above, is used in a motorcycle.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention arranges the main body of the heat-insulating cooling channel between the lower end face of the cylinder head and the exhaust port, and allows it to pass through this area. It adopts the dual effect of chamber heat insulation and liquid cooling to achieve the desired effect. The cooling medium flows directly through the area with the most concentrated heat, which can reduce the working temperature of the area below the exhaust port from 308°C to below 220°C, which is lower than the aging temperature of the cylinder head material (above 230°C). This avoids excessive hardness reduction caused by material annealing and prevents plastic deformation caused by excessive heat load from the root.

[0020] 2. This invention reduces the deformation of the cylinder head exhaust side by making the cross-section of the main section of the cooling channel flat and wider than its height, and by defining its position relative to the lower end face and the exhaust passage. This ensures that the channel is close to the high-heat area and easily deformable edges, thus meeting the flatness requirements of the cylinder head exhaust side. At the same time, the wall thickness between the newly added oil passage and the lower end face of the cylinder head is strictly controlled to prevent the lower end face of the cylinder head from deforming due to excessive thickness, while excessive thickness will not fully realize the cooling effect. This design is the result of precise calculations and multiple experimental verifications.

[0021] 3. The preferred cooling medium in this invention is cooling oil, which can utilize the existing lubrication system of the original engine without additional cost. An oil inlet and outlet are set up to form a circulating flow, ensuring a continuous and stable cooling effect. The amount of cooling oil entering this oil passage needs to be strictly controlled. Too much oil will reduce the amount of lubricating oil in other parts, leading to poor lubrication. Too little oil will not achieve the best cooling effect. Therefore, after CFD analysis and multiple experimental verifications, the total amount of cooling oil entering the cylinder head and its distribution ratio are controlled by the diameter of the oil passage hole of the cylinder head gasket. Attached Figure Description

[0022] Figure 1 A schematic diagram of the internal cooling oil passages of an existing cylinder head;

[0023] Figure 2 This is a diagram showing the layout of the internal cooling oil passages and exhaust passages of an existing cylinder head.

[0024] Figure 3 A photograph of an existing cylinder with blow-by gas on the exhaust side;

[0025] Figure 4 A photograph of the actual object used for testing the flatness of the exhaust side of an existing cylinder;

[0026] Figure 5 This is a schematic diagram of the cylinder head structure and its internal exhaust-side cooling structure according to Embodiment 1 of the present invention;

[0027] Figure 6 This is a perspective view of the cylinder head structure and its internal exhaust-side cooling structure according to Embodiment 1 of the present invention;

[0028] Figure 7 This is a diagram showing the positional relationship between the heat insulation cooling channel, the original cooling channel, and the cylinder head exhaust channel in Embodiment 1 of the present invention.

[0029] Figure 8 This is a photograph of the actual cylinder exhaust side without blow-by in Embodiment 1 of the present invention;

[0030] Figure 9 This is a photograph of the actual object used for cylinder exhaust side flatness testing in Embodiment 1 of the present invention;

[0031] Figure 10 This is a structural diagram of the heat insulation cooling channel in Embodiment 2 of the present invention.

[0032] In the diagram, 1 - cylinder head, 2 - heat insulation cooling channel, 3 - oil inlet, 4 - oil outlet, 5 - cylinder head exhaust channel, 6 - original cooling channel, and 7 - lower end face of the cylinder head. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] Example 1:

[0036] See Figure 5 and Figure 6 This invention provides a heat-insulating cooling structure for the exhaust side of a cylinder head. Specifically, a heat-insulating cooling channel 2 is added to the cylinder head casting 1. The main body of the heat-insulating cooling channel 2 is located between the lower end face 7 of the cylinder head and the exhaust passage 5 of the cylinder head. The oil inlet 3 of the heat-insulating cooling channel 2 is located on the lower end face 7 of the cylinder head and is connected to the engine oil supply system (such as an oil pump, supplying oil through the internal oil passages of the engine block). The oil outlet 4 is connected to the return system (such as the oil pan). The oil outlet 4 is located on the side wall of the chain cavity of the cylinder head. The chain cavity is a chamber inside the cylinder head used to accommodate the timing chain, and its internal space is usually connected to the engine oil pan, thus forming part of the lubricating oil circulation path. After the oil outlet 4 of the heat-insulating cooling channel connects to the side wall of the chain cavity, the cooling oil flows into the chain cavity through the oil outlet, flows downwards along the chain cavity wall or the surface of components such as the chain tensioner, and finally returns the cooling medium to the return oil sump, achieving cooling oil return. The oil outlet 4 of the heat insulation cooling channel 2 can also be set on the lower end face 7 of the cylinder head; during assembly, the oil outlet 4 is aligned with the corresponding oil return hole on the cylinder body 1, and the cooling oil flows out from the oil outlet 4 and directly enters the oil return hole of the cylinder body, and flows back to the oil pan along the oil return channel inside the cylinder body.

[0037] The oil outlet of the heat-insulating cooling channel 2 can also be located on the side wall of other existing oil return channels inside the cylinder head. These "other oil return channels" refer to pre-existing oil channels inside the cylinder head besides the heat-insulating cooling channel described in this application, such as the return section of the existing combustion chamber cooling oil circuit. The cooling oil in the heat-insulating cooling channel 2 flows into this existing oil return channel through the outlet, merging with the existing cooling oil in the channel and flowing back to the return system along the channel. This structure makes full use of the existing oil circuit resources inside the cylinder head, avoiding the need to add new independent oil return channels, which helps simplify the internal structure of the cylinder head and reduces casting and machining difficulties.

[0038] The main section of the heat-insulating cooling channel 2 passes through the area between the lower end face of the cylinder head and the exhaust port. Spatially, the heat-insulating cooling channel 2 enters from one side of this area and exits from the other side, ensuring that the cooling medium can cover the entire critical area. This arrangement makes the cooling effect more uniform and avoids local overheating.

[0039] like Figure 7 The diagram shown illustrates the positional relationship between the heat-insulating cooling channel 2, the original cooling channel 6, and the cylinder head exhaust channel 5 in Example 1. Figure 7It can be seen that the structure of the original cooling channel 6 and the oil inlet and outlet remain unchanged. The main body of the heat-insulating cooling channel 2 and the cylinder head exhaust channel 5 are spatially intersecting. That is, the heat-insulating cooling channel 2 is located between the cylinder head exhaust channel 5 and the lower end face 7 of the cylinder head, and the heat-insulating cooling channel 2 is connected in parallel with the combustion chamber cooling channel. When the internal combustion engine is working, the heat-insulating cooling channel 2 prevents heat from being conducted from the high-temperature area such as the exhaust channel 5 to the lower end face 7 (mounting surface) area of ​​the cylinder head. At the same time, the cooling oil continuously flows through the heat-insulating cooling channel 2, and the heat between the exhaust channel and the lower end face is dissipated through convection heat exchange, reducing the temperature of the part below the exhaust channel and preventing material annealing. The heat-insulating cooling channel 2 is used for the flow of cooling medium. In this embodiment, the cooling medium is cooling oil, which is a readily available medium in the internal combustion engine and does not require additional system costs.

[0040] The main section of the insulated cooling channel 2 has a flat cross-section, with its width greater than its height. Within the confined space of the workpiece, the flat structure increases the contact area between the cooling medium and the surrounding metal, thereby improving the heat dissipation efficiency per unit length of the channel. The oil inlet and outlet of the cooling channel are used to connect to the oil supply system, and the oil outlet is used to connect to the return system. New cooling oil is introduced through the oil inlet, and the hot oil that has absorbed heat is carried away through the oil outlet, forming a continuous circulation process. This ensures that the cooling medium in the channel always maintains a low inlet temperature, thus providing stable and long-lasting cooling.

[0041] In this embodiment, the cooling medium flows directly through the high-heat area between the cylinder head exhaust passage 5 and the lower end face 7 of the cylinder head. Forced convection heat transfer removes heat from this area, thereby reducing the temperature below the exhaust passage and preventing material annealing and hardness reduction due to excessive heat load. Simultaneously, the flow channel of the cooling medium enhances the effect of the physical isolation layer, introducing a significant thermal resistance into the original metal heat transfer path, blocking direct heat conduction from the exhaust passage to the lower end face, and solving the problem of gas leakage caused by thermal deformation in this area. This ensures that the cooling medium flows and covers the entire critical area, avoiding uneven cooling caused by the channel only overlapping the edge of the area, resulting in more thorough cooling. This effectively reduces the temperature of the entire area below the exhaust passage, minimizing localized overheating and thus more reliably preventing localized plastic deformation.

[0042] Structural Description: In this application and the accompanying drawings, the lower end face 7 of the cylinder head refers to the bottom surface of the cylinder head facing the cylinder block; the cylinder head exhaust passage 5 refers to the passage inside the cylinder head that connects to the combustion chamber and is used to exhaust exhaust gas; the main body section of the heat insulation cooling passage 2 refers to the part of the cooling passage used for main cooling, which is the middle section excluding the areas near the inlet and outlet; the outer end refers to the end of the cooling passage that is closest to the outer wall of the cylinder head exhaust side in the extension direction.

[0043] For the Y10 internal combustion engine, a single-cylinder, four-stroke, oil-cooled engine with an SOHC (single overhead camshaft) four-valve structure, a displacement of 278.3 ml, a compression ratio of 9.6, a maximum power of 18.5 kW, and a maximum torque of 24 N·m, this embodiment defines the main section of the heat-insulating cooling channel 2 as having a flat cross-section, with its width W greater than its height H. In specific implementation, the width W = 10 mm, the height H = 4 mm, and the width-to-height ratio W / H = 2.5 (satisfying W / H ≥ 2). The flat cross-section increases the contact area between the cooling medium and the metal, improving heat dissipation efficiency. Furthermore, combined with the flat main section passing under the cylinder head exhaust passage 5, its wider top surface can cover a wider area at the bottom of the exhaust passage, forming "surface cooling" rather than the "line cooling" of a traditional circular channel. Specifically, assuming the width requiring cooling at the bottom of the exhaust duct is 15mm, the effective coverage width of a circular channel (4mm in diameter) is only about 4mm, with a coverage rate of less than 27%. In contrast, the effective coverage width of a flat channel (10mm wide) can reach 10mm, with a coverage rate of approximately 67%. When the width is further increased to 12mm, the coverage rate can reach over 80%. As long as the corresponding wall thickness requirements are met, the coverage rate can be further increased. Compared to the traditional circular channel, the diameter is limited due to height constraints. In this embodiment, the heat exchange area of ​​the flat main section is significantly increased, allowing the cooling medium to absorb the heat emitted from the bottom of the exhaust duct more efficiently. This results in a lower metal temperature at the same flow rate and velocity, further suppressing material annealing and deformation. Experiments show that using a flat channel with an aspect ratio ≥2 can further reduce the metal temperature below the exhaust duct.

[0044] Meanwhile, to avoid thinning of the cylinder head wall due to the installation of the heat-insulating cooling channel 2, which could lead to fatigue cracks under long-term alternating loads, this embodiment limits the distance between the main body of the cooling channel and the lower end face of the cylinder head to no more than 10mm, and the distance from the exhaust passage to no more than 10mm. In specific implementations, these distances are 8mm and 6mm, respectively. Simulations and experiments show that when the distance is controlled within 10mm, the temperature in the area below the exhaust passage can be reduced to below 230℃, effectively preventing annealing.

[0045] In this embodiment, the distance between the outer end of the main body of the heat-insulating cooling channel 2 and the outer wall of the cylinder head exhaust side is limited to no more than 10 mm. In actual implementation, this distance is 5 mm. Since the outer edge of the cylinder head exhaust side is the area with the most significant deformation, extending the cooling channel close to this edge can directly improve the bending stiffness of the edge, limit outward bulging deformation, and thus more effectively prevent gas leakage.

[0046] This embodiment limits the minimum wall thickness of the main body of the heat-insulating cooling channel 2 between the main body and the lower end face 7 of the cylinder head, the minimum wall thickness between the channel and the exhaust channel, and the minimum wall thickness between the channel and the outer wall of the cylinder head exhaust side to no less than 3mm. In specific implementations, the aforementioned minimum wall thicknesses are 3.2mm, 3.5mm, and 3.0mm, respectively. This minimum wall thickness ensures the feasibility of the casting process, avoids shrinkage cavities and cracks, and ensures the structural integrity of the cylinder head under long-term high-temperature and high-pressure cycling. Through casting simulation and fatigue strength calculations, if the wall thickness at a certain point is less than 3mm, the aluminum liquid will not fill the mold sufficiently under casting conditions, easily leading to cold shuts and shrinkage porosity; at the same time, under the thermal cycling effect of a 200℃ temperature difference, the thermal stress at that point can exceed the fatigue limit of the aluminum alloy (approximately 50-60MPa), leading to the initiation of thermal fatigue cracks. Therefore, 3mm is the minimum safe wall thickness.

[0047] To address the issue of excessively large or small oil inlets in the cylinder head oil chamber disrupting the fluid-oil balance, this invention also systematically studies and verifies the oil inlet control of the heat-insulating cooling channel 2. Since the oil inlet of the heat-insulating cooling channel is directly or indirectly connected to the engine's lubrication system (oil supply system), a reasonable design of the inlet size is crucial for ensuring the cooling effect of the heat-insulating cooling channel and the stable operation of the entire engine lubrication system.

[0048] Specifically, if the oil intake of the heat-insulating cooling channel is too large, a large amount of coolant will enter the channel, causing a drop in the main oil pressure of the engine. This affects the normal lubrication of other moving parts (such as the crankshaft, connecting rods, camshaft, rocker arms, etc.), and in severe cases, may lead to major failures such as bearing erosion and camshaft wear. Simultaneously, excessive coolant flow at a high velocity within the heat-insulating cooling channel will shorten the heat exchange time between the coolant and the wall, reducing heat dissipation efficiency and creating the paradox of "overcooling but inefficient." Conversely, if the oil intake is too small, sufficient forced convection heat transfer cannot be achieved, and the metal temperature in the area below the exhaust manifold cannot be effectively reduced, potentially leading to annealing and hardness decay, failing to solve the blow-by problem. Therefore, it is necessary to rationally allocate the proportion of oil entering the heat-insulating cooling channel based on the lubricating oil pump's supply characteristics under engine idling conditions to simultaneously meet the cooling effect and the lubrication needs of the main oil circuit.

[0049] In the preferred embodiment, based on an engine idle speed of 1500 r / min and the oil pump supply rate, and assuming that 40% of the total oil pump supply can be used for cylinder head cooling oil distribution, multiple comparative tests were conducted on the oil inlet flow rate of the heat insulation cooling channel. The oil inlet flow rate is controlled by setting flow-limiting holes on the cylinder head gasket (i.e., the sealing gasket between the cylinder head and cylinder block) at the position corresponding to the oil inlet of the heat insulation cooling channel. The diameter of the flow-limiting hole directly determines the flow rate of cooling oil entering the heat insulation cooling channel. Furthermore, setting flow-limiting holes through the gasket has the advantages of simple structure, easy replacement and adjustment, and no increase in the machining difficulty of the cylinder head body. Flow-limiting holes of different diameters were made on the cylinder head gasket, and the cooling effect of the heat insulation cooling channel and its impact on the main oil circuit pressure were tested under each scheme.

[0050] The flow distribution ratios corresponding to different flow restrictor orifice diameters are shown in Table 1:

[0051]

[0052] Table 1

[0053] After multiple rounds of bench tests, in this embodiment 1, with the flow-limiting orifice diameter set to Φ4.0mm, the oil volume allocated to the isolation channel accounts for approximately 28% of the total oil supply from the oil pump (based on an idle speed of 1500 r / min, the portion of the oil supply system that can be used for cylinder head cooling). Under this scheme, the temperature in the area below the exhaust port can be stably maintained at around 220℃, far below the aging temperature of the cylinder head material (above 230℃), effectively preventing material annealing and hardness decay; at the same time, it does not significantly affect the normal lubrication of other moving parts of the engine, and the overall lubricating oil pressure remains within the design allowable range.

[0054] The specific orifice diameter (Φ4.0mm) and corresponding oil distribution ratio (28%) of the aforementioned flow restrictor are optimized values ​​obtained based on test data of a specific engine model (Y10 internal combustion engine) (parameters such as displacement, bore, stroke, and rated power). For internal combustion engines of different displacements and power ratings, those skilled in the art can determine the appropriate orifice diameter and oil distribution ratio through a limited number of tests, taking into account factors such as the specific engine's lubricating oil pump flow characteristics, idle speed, and oil circuit layout.

[0055] To further verify the universality and stability of the technical solution of this application, the cylinder head manufactured using the solution of Embodiment 1 was subjected to the following test: the engine equipped with the cylinder head of this embodiment was operated alternately under different operating conditions such as idle speed, rated power, and maximum torque, with each operating condition lasting 30 minutes, for a total cycle of 300 hours. Post-test testing showed that the temperature in the area below the exhaust manifold remained stable below 230℃ under all operating conditions, the exhaust side flatness was 0.07mm, and there were no signs of blow-by.

[0056] The results are shown in Table 2:

[0057]

[0058] Table 2

[0059] See Figure 8 This is a photograph of the actual cylinder exhaust side without blow-by in Embodiment 1 of the present invention; Figure 9 This is a photograph of the actual object used for testing the flatness of the cylinder exhaust side surface in Embodiment 1 of the present invention. The above measured data and photographs fully demonstrate that the present invention, by arranging the cooling channel between the lower end face of the cylinder head and the exhaust channel, and optimizing its cross-sectional shape, distance, wall thickness, and other designs, can significantly reduce the heat load in the area below the exhaust channel, prevent material annealing and hardness decay, and effectively solve the problem of gas leakage caused by thermal deformation.

[0060] Example 2:

[0061] As an optimization, the positions of the oil inlet 3 and oil outlet 4 of the heat insulation cooling channel 2 of the present invention can be flexibly set according to the overall oil circuit layout of the cylinder head, casting process and space constraints.

[0062] See Figure 10 The heat-insulating cooling channel 2 is independently set up. Its oil inlet and outlet are located on the lower end face of the cylinder head and the outer wall of the cylinder head, respectively. An independent external pipeline is connected to the oil outlet 4, and the other end of the external pipeline is connected to a return system (such as an oil pan or return sump). The advantage of this scheme is that the return path is independent, not limited by the internal structure of the cylinder head, and does not require large-scale modifications to the existing oil passages inside the cylinder head. Specifically, the cooling oil from the internal combustion engine block is divided into two paths: one enters the combustion chamber cooling oil passage to cool the top area of ​​the combustion chamber; the other enters the cooling channel in parallel to cool the area below the exhaust passage. After completing their respective heat exchange, the two cooling oil paths return to the cooling oil return system (such as an oil pan) separately or together. This parallel arrangement ensures that the two oil flows are independent and do not interfere with each other.

[0063] In addition, the heat insulation cooling channel 2 is not limited to one oil inlet. For example, if the cylinder head space allows, two oil inlets can be provided (supplying oil from both sides respectively) to improve flow uniformity and redundancy reliability.

[0064] Example 3:

[0065] As an optimization, the minimum wall thickness between the main body of the heat-insulating cooling channel 2 and the lower end face 7 of the cylinder head, the minimum wall thickness between it and the cylinder head exhaust passage 5, and the minimum wall thickness between it and the outer wall of the cylinder head exhaust side are all not less than 3 mm. Excessively thin walls can lead to casting defects (such as shrinkage cavities and cracks) and the risk of cracking during operation due to concentrated thermal and mechanical stress. By setting a lower limit of 3 mm, it is ensured that the cooling channel provides cooling without affecting the strength and durability of the cylinder head itself.

[0066] Example 4:

[0067] As an optimization, air can also be used as the cooling medium in the insulated cooling channel 2. Air, as a medium with a low thermal conductivity, has excellent thermal insulation properties. When air is introduced into the insulated cooling channel or an air layer is formed by natural convection, the low thermal conductivity of air allows it to form an effective thermal resistance layer between the exhaust port and the lower end face of the cylinder head, blocking or reducing heat conduction from the exhaust port to the lower end face. Since the thermal conductivity of air is much lower than that of metal materials, inserting an air-filled isolation channel into the original direct metal heat transfer path is equivalent to setting a significant thermal resistance in the heat conduction path, forcing heat to be transferred through a complex "metal-air-metal" process. In addition, when the insulated cooling channel is connected to the external environment to form an air inlet and outlet, air can also form natural or forced convection within the channel, carrying away some heat and playing a role in heat dissipation.

[0068] Furthermore, while cooling oil is the preferred choice in practical implementation, those skilled in the art will understand that other coolants (such as water-based coolants and mixed coolants) can also achieve a cooling effect to some extent, but additional equipment (such as independent coolant pumps, radiators, and sealing systems) is required. Therefore, in specific application scenarios, the aforementioned alternative media can also be used.

[0069] In summary, the technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. By arranging the main body of the channel between the lower end face of the cylinder head and the exhaust port, and allowing it to pass through this area, heat is isolated from the high-temperature areas such as the exhaust port to the lower mounting surface of the cylinder head. At the same time, the internal cooling medium flows directly through the area where the heat is most concentrated. Under the dual effects of heat insulation and cooling, the working temperature of this area can be reduced to below the aging temperature of the cylinder head material, thereby avoiding material annealing and hardness decay, and fundamentally preventing blow-by problems caused by plastic deformation due to excessive heat load. This invention has a compact structure and significant cooling effect, and can be widely used in internal combustion engine cylinder heads.

[0070] This invention also discloses the application of the cylinder head exhaust-side cooling structure in the cylinder head of an internal combustion engine. This cylinder head can be directly mounted onto the internal combustion engine and connected to the existing oil supply and return lines on the engine block, replacing the existing cylinder head to solve the blow-by problem. During assembly, only corresponding oil passage holes need to be set at the corresponding positions on the cylinder head gasket to achieve connection with the cylinder block's oil lines, without requiring additional modifications to the engine block, thus exhibiting good compatibility. The described internal combustion engine (cylinder head) is suitable for power equipment such as motorcycles.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A cylinder head exhaust side heat shield cooling structure characterized by comprising: To add a heat-insulating cooling channel to the cylinder head casting, the heat-insulating cooling channel is located between the lower end face of the cylinder head and the exhaust port of the cylinder head. The heat-insulating cooling channel and the exhaust port of the cylinder head are spatially intersected, and the cooling channel is used for the flow of cooling medium.

2. The exhaust side insulated cooling structure of a cylinder head according to claim 1, characterized by The main body of the heat-insulating cooling channel passes through the area between the lower end face of the cylinder head and the exhaust port; the heat-insulating cooling channel has at least one oil inlet and at least one oil outlet, the oil inlet is used to communicate with the oil supply system, and the oil outlet is used to communicate with the return system.

3. The exhaust side insulated cooling structure of a cylinder head according to claim 2, characterized by The oil inlet is located on the lower end face of the cylinder head and is connected to the engine oil supply system; the oil outlet is located on the side wall of the chain cavity of the cylinder head and is connected to the return system.

4. The exhaust side insulated cooling structure of a cylinder head according to claim 2, characterized by The heat insulation cooling channel is set independently. The oil inlet is located on the lower end face of the cylinder head. The oil outlet is located on the chain cavity side wall, the lower end face of the cylinder head, or the outer wall of the cylinder head. An independent external pipeline is connected to the oil outlet. The other end of the external pipeline is connected to the return system.

5. The exhaust side insulated cooling structure of a cylinder head according to claim 1, characterized by The main section of the heat-insulating cooling channel has a flat cross-section, and its width is greater than its height; the ratio of the width W to the height H of the main section of the cooling channel satisfies: W / H≥2.

6. The exhaust side insulated cooling structure of a cylinder head according to claim 1, characterized by The distance between the main body of the heat insulation cooling channel and the lower end face of the cylinder head is no more than 10mm, and the distance between it and the exhaust channel is no more than 10mm.

7. The exhaust side insulated cooling structure of a cylinder head according to claim 1, characterized by The distance between the outer end of the main body section of the heat-insulating cooling channel and the outer wall of the cylinder head exhaust side is no more than 10mm.

8. The exhaust side insulated cooling structure for a cylinder head according to claim 1, characterized by: The minimum wall thickness between the main body of the heat insulation cooling channel and the lower end face of the cylinder head, the minimum wall thickness between the channel and the exhaust channel, and the minimum wall thickness between the channel and the outer wall of the cylinder head exhaust side are all not less than 3mm.

9. A cylinder head having resistance to deformation, characterized by Includes the cylinder head exhaust side heat insulation and cooling structure as described in any one of claims 1 to 8.

10. An internal combustion engine characterized by comprising: It includes the cylinder head as described in claim 9 and is used in motorcycles.

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