Rotary valve cylinder head

Abstract

The application discloses a rotary valve cylinder cover, which comprises a cylinder cover, an internal combustion chamber, an air inlet, an air outlet and an air port communicated with the internal combustion chamber, the air inlet and the air outlet are arranged on two sides of the cylinder cover, and the air port is arranged below the rotary valve; the rotary valve is rotatably arranged in the cylinder cover through a rotary valve shaft, and a semilunar groove is arranged on the outer circumferential surface of the rotary valve; when the rotary valve rotates according to the crankshaft of the engine at a predetermined timing, the semilunar groove sequentially passes through the air inlet, the air outlet and the air port to selectively open or close the air inlet, the air outlet and the air port; a transmission mechanism is used for connecting the crankshaft of the engine and the rotary valve shaft to realize timing transmission of the crankshaft of the engine and the rotary valve; and a sealing system is arranged between the cylinder cover and the rotary valve shaft to prevent gas leakage. The semilunar groove on the rotary valve shaft is rotated to selectively open and close the air passage, so that the engine gas exchange process is controlled by replacing the traditional valve type valve train.

Description

Technical Field

[0001] This invention relates to the field of mechanical engineering technology, and more specifically to a rotary valve cylinder head. Background Technology

[0002] Currently, small-displacement engines are widely used in motorcycles and other fields, creating an urgent need for energy conservation, emission reduction, and industrial upgrading. Traditional reciprocating valve train systems have long suffered from inherent defects such as complex structure, redundant parts, susceptibility to valve suspension and vibration at high speeds, and unstable scavenging efficiency. These directly lead to insufficient fuel economy and excessive pollutant emissions, becoming a key bottleneck restricting equipment performance improvement and green industrial development. Promoting the transformation of valve train systems towards simplified structure and high efficiency has become a core development trend in this field.

[0003] Domestic research on rotary valve technology has been dominated by breakthroughs in practical applications, and a complete technology chain has been established. In terms of core structure, Deng Baoqing's team pioneered the innovative design of single and dual rotary valve engines, replacing traditional mechanisms and laying a solid structural foundation. Li Shihang improved the dual rotary valve cylinder head design, verified it through ANSYS simulation, and developed a 3D printing process, establishing a closed loop of "design-simulation-manufacturing." However, the issues of precision and cost in mass production remain unresolved. Regarding control adaptation, Zhang Bo developed a fuel injection system based on the STM32F103C8T6, verifying its feasibility through MAP optimization, but did not fully consider the coordinated control with the ignition system. Furthermore, Zhao Chenyang and Lin Hao invented a shaft valve engine with a 1:2 speed ratio between the shaft valve and crankshaft; Shi Lisong proposed a through-type rotary valve mechanism with a 1:4 speed ratio, enriching the structural design. However, neither of these designs is adapted to the layout of multi-cylinder engines in small-displacement motorcycles, and neither addresses how to solve the dynamic sealing problem between the rotary valve and the cylinder head. Overall, domestic research highlights practical applications, but there are still significant shortcomings in areas such as multi-cylinder engine adaptation, synergistic optimization of sealing and cost, quantitative analysis of multiple systems, and long-term durability verification.

[0004] Research abroad started earlier, focusing on fundamental principle exploration and quantitative performance analysis. Japanese scholars pioneered research in the 1980s; in 1996, American scholar Wallis proposed an axial intake and exhaust rotary valve design, but it was only applicable to single-cylinder engines, limiting its application scenarios; while the British RCV engine achieved technological innovation, its complex structure and poor fuel economy prevented large-scale application. In terms of quantitative analysis, Wenbo Dong and Vishwas N. Bedekar used Python to build a predictive model, measuring that the maximum opening area of ​​the rotary valve was lower than that of a traditional valve, but it maintained a stable efficiency of approximately 54% within a specific range at 2900 rpm. However, this study only used a single operating condition comparison, without in-depth analysis of high-speed variable load dynamic performance, nor did it study long-term wear and fatigue durability.

[0005] In summary, significant progress has been made both domestically and internationally in the structural design, performance verification, and control development of rotary valve technology. However, these advancements all face common technical bottlenecks such as high manufacturing costs, poor sealing performance, insufficient compatibility with multi-cylinder engines, lack of multi-system collaborative optimization, and absence of long-term reliability verification. Furthermore, there are significant research gaps in specific areas such as dedicated design for multi-cylinder engines in small-displacement motorcycles, collaborative optimization of sealing and cost, and quantitative analysis of multi-system coupling. Summary of the Invention

[0006] The purpose of this invention is to provide a rotary valve cylinder head that selectively opens and closes the air passage by rotating a crescent-shaped groove on the rotary valve shaft, thereby replacing the traditional valve-type valve train mechanism to control the engine's scavenging process.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A rotary valve cylinder head includes: a cylinder head, a rotary valve, a transmission mechanism, and a sealing system; The cylinder head has a combustion chamber, an intake port, an exhaust port, and a port communicating with the combustion chamber. The intake port and the exhaust port are respectively located on both sides of the cylinder head, and the port is located below the rotary valve. The rotary valve is rotatably mounted inside the cylinder head via a rotary valve shaft, and a crescent-shaped groove is provided on the outer circumferential surface of the rotary valve. The crescent-shaped groove is configured such that when the rotary valve rotates with the crankshaft of the engine at a predetermined timing, the crescent-shaped groove sequentially passes through the intake port, the exhaust port, and the air inlet to selectively open or close, thereby realizing sequential control of the engine's exhaust, intake, compression, and power strokes. A timing drive mechanism is used to connect the crankshaft of the engine to the rotary valve shaft to achieve timing drive between the crankshaft of the engine and the rotary valve. A sealing system is provided between the cylinder head and the rotary valve shaft to prevent gas leakage.

[0008] Furthermore, the outer surface of the cylinder head is provided with heat dissipation fins, specifically elliptical cross-section structures.

[0009] Furthermore, the central angle of the crescent-shaped groove of the rotary valve is 125°, and the angle between the upper edge of the intake and exhaust passages on the cylinder head and the center of the air port is 129°.

[0010] Furthermore, the rotary valve shaft is supported by a needle roller bearing, which is a cage-type bearing without an inner ring.

[0011] Furthermore, the diameter of the rotary valve shaft is 0.85 times the cylinder diameter, and the effective flow length of the crescent-shaped groove corresponding to the air port is 0.8 times the cylinder diameter.

[0012] Furthermore, the timing transmission mechanism includes: timing pulleys respectively disposed on the crankshaft of the engine and the rotary valve shaft, and a toothed belt connecting the timing pulleys, so as to realize a timing transmission with a transmission ratio of 2:1 between the crankshaft of the engine and the rotary valve shaft.

[0013] Furthermore, the sealing system includes: an axial sealing structure and a circumferential sealing structure; An axial sealing structure is provided at the axial gap between the two ends of the rotary valve shaft and the cylinder head; the shaft end sealing structure includes at least two elastic open sealing rings, the sealing rings are assembled in the annular groove of the rotary valve shaft and do not rotate with the rotary valve shaft, and the openings of adjacent two sealing rings are staggered to form a labyrinth sealing structure. A circumferential sealing structure is provided at the spacer between the air inlet, the exhaust outlet and the combustion chamber, including at least one sealing strip and an elastic element that provides pre-tightening force to the sealing strip. The sealing strip is configured to be pressed against the surface of the rotary valve shaft under the action of high-pressure gas in the combustion chamber.

[0014] Furthermore, the two adjacent sealing rings of the axial sealing structure are respectively provided with mutually cooperating concave-convex locking structures to restrict the relative sliding of the sealing rings and maintain the opening misalignment state.

[0015] Furthermore, guide sliders are provided at both ends of the sealing strip to prevent the sealing strip from rolling on the surface of the rotary valve shaft.

[0016] According to specific embodiments provided by the present invention, the present invention has the following technical effects compared to the prior art: This invention fundamentally simplifies the overhead engine structure by replacing the traditional complex reciprocating valve, spring, and camshaft valve train with a rotary valve shaft featuring a crescent-shaped groove. This significantly reduces the number of moving parts, overall weight, and mechanical friction losses. The symmetrical layout, with the intake and exhaust ports positioned on opposite sides of the cylinder head and opposite the rotary shaft, combined with the precise selective opening and closing of the intake and exhaust ports during continuous rotation of the rotary valve shaft, not only completely eliminates the reciprocating inertial force and impact noise generated during traditional valve opening and closing, but also significantly improves intake and exhaust efficiency and airflow smoothness. Furthermore, it provides a structural foundation for the engine to overcome speed bottlenecks, achieve faster power response, and more precise valve train control. Simultaneously, a reliable transmission mechanism ensures strict timing coordination with the crankshaft, while a specially designed sealing system effectively overcomes the technical barrier of easy leakage in rotary valve train structures, ensuring absolute airtightness of the combustion chamber under high-pressure extreme conditions. Ultimately, while achieving engine lightweighting, high speed, and low friction, it comprehensively guarantees and improves the overall combustion efficiency, power output stability, and fuel economy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] The present invention provides a rotary valve cylinder head in further detail below with reference to the accompanying drawings. Figure 1 This is a schematic diagram of the basic structure of the rotary valve engine in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the working principle of the rotary valve engine in Embodiment 1 of the present invention; wherein (a) is the exhaust stroke; (b) is the intake stroke; (c) is the compression stroke; and (d) is the power stroke. Figure 3 This is a schematic diagram of the cylinder head cooling fins in Embodiment 1 of the present invention.

[0019] In the diagram: 1. Cylinder head; 2. Rotary valve; 3. Piston; 4. Engine block; 5. Connecting rod; 6. Crankshaft. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0022] Example 1 like Figure 1 As shown, the present invention provides a rotary valve cylinder head, comprising: a cylinder head 1, a rotary valve 2, a transmission mechanism, and a sealing system; The cylinder head 1 has a combustion chamber, an intake port, an exhaust port, and a port communicating with the combustion chamber. The intake port and the exhaust port are respectively located on both sides of the cylinder head 1, and the port is located below the rotary valve 2. The outer surface of the cylinder head is provided with heat dissipation fins, which are specifically elliptical cross-section structures.

[0023] The rotary valve 2 is rotatably disposed inside the cylinder head 1, and a crescent-shaped groove is provided on the outer circumferential surface of the rotary valve 2; the crescent-shaped groove is configured such that when the rotary valve 2 rotates with the crankshaft of the engine at a predetermined timing, the crescent-shaped groove sequentially passes through the intake port, the exhaust port, and the air port to selectively open or close, so as to realize the sequential control of the engine's exhaust, intake, compression, and power strokes; The central angle of the crescent-shaped groove of the rotary valve 2 is 125°, and the angle between the upper edge of the intake and exhaust passages on the cylinder head and the center of the air port is 129°.

[0024] The rotary valve shaft is supported by a needle roller bearing, which is a cage-type bearing without an inner ring.

[0025] The diameter of the rotary valve shaft is 0.85 times the cylinder diameter, and the effective flow length of the crescent-shaped groove corresponding to the air port is 0.8 times the cylinder diameter.

[0026] A timing transmission mechanism is used to connect the crankshaft of the engine and the shaft of the rotary valve to realize the timing transmission between the crankshaft of the engine and the rotary valve. The timing transmission mechanism includes: timing pulleys respectively disposed on the crankshaft of the engine and the rotary valve shaft, and a toothed belt connecting the timing pulleys, so as to realize a timing transmission with a transmission ratio of 2:1 between the crankshaft of the engine and the rotary valve shaft.

[0027] A sealing system is provided between the cylinder head 1 and the rotary valve shaft to prevent gas leakage.

[0028] The sealing system includes: an axial sealing structure and a circumferential sealing system; An axial sealing structure is provided at the axial gap between the two ends of the rotary valve shaft and the cylinder head; the shaft end sealing structure includes at least two elastic open sealing rings, the sealing rings are assembled in the annular groove of the rotary valve shaft and do not rotate with the shaft, and the openings of adjacent two sealing rings are staggered to form a labyrinth sealing structure. A circumferential sealing structure is provided at the spacer between the air inlet, the exhaust outlet and the combustion chamber, including at least one sealing strip and an elastic element that provides pre-tightening force to the sealing strip. The sealing strip is configured to be pressed against the surface of the rotary valve shaft under the action of high-pressure gas in the combustion chamber.

[0029] The two adjacent sealing rings of the axial sealing structure are respectively provided with mutually cooperating concave-convex locking structures to restrict the relative sliding of the sealing rings and maintain the opening misalignment state.

[0030] The sealing strip is provided with guide sliders at both ends to prevent the sealing strip from rolling sideways on the surface of the rotary valve shaft.

[0031] In this embodiment, the basic structure of the rotary valve engine is shown in Figure 1, which mainly consists of a cylinder head 1, a rotary valve 2, an engine block 4, a piston 3, a connecting rod 5, and a crankshaft 6.

[0032] The cylinder head assembly uses a grooved rotary valve and sealing mechanism, replacing the traditional engine's valve train. Timing transmission between the crankshaft and the rotary valve shaft is achieved via timing pulleys and toothed belts mounted on the front ends of the crankshaft and rotary valve shaft, respectively. The transmission ratio is the same as in a four-stroke engine, 2:1—meaning the rotary valve rotates once for every two crankshaft rotations. The cylinder head has an intake port (left side), an exhaust port (right side), and a port connecting to the combustion chamber (located below the rotary valve). The rotary valve has a crescent-shaped groove machined on it, which controls the opening and closing of the intake and exhaust ports, thereby regulating the intake and exhaust process.

[0033] The concept of air-fuel mixture combustion is shared by rotary valve engines and traditional engines; in this embodiment, the four strokes of exhaust, intake, compression, and power are also fully adopted in the rotary valve engine. Figure 2 The diagram in (a) shows the exhaust stroke of the engine: the crankshaft rotates clockwise, driving the piston upward; at the same time, the rotary valve also rotates clockwise under the drive of the timing belt, and its control groove connects the exhaust port to the cylinder, allowing the exhaust gas in the cylinder to be discharged. Figure 2 (b) is the intake stroke: the crankshaft rotates clockwise, and the piston moves downward accordingly; the rotary valve rotates clockwise synchronously under the drive of the timing belt, and the control groove connects the intake port with the cylinder, so that outside air is drawn into the cylinder; at the same time, the injector injects fuel into the cylinder (see the engine assembly diagram below for details). Figure 2 (c) is the compression stroke: the crankshaft rotates clockwise and the piston moves upward; the rotary valve rotates clockwise under the drive of the timing belt, its control groove is not connected to the cylinder, the cylinder is in a closed state, and the air-fuel mixture in the cylinder is compressed; when the piston approaches the top dead center, the spark plug ignites (see the engine assembly diagram below for details). Figure 2 In the middle (d) stroke: the control groove of the rotary valve is not connected to the cylinder, the cylinder remains closed, the high temperature and high pressure gas inside the cylinder pushes the piston to do work, which in turn drives the crankshaft to rotate clockwise at an accelerated speed, thus completing one working cycle.

[0034] Example 2 To verify the effectiveness of the rotary valve cylinder head in Example 1, the present invention also conducted the following data verification process: Based on the technical parameters of the 125cc engine, the key dimensions of the combustion chamber were determined through theoretical calculations to ensure that the overall performance requirements of the engine are met.

[0035] 1. Determination of basic parameters The core basic parameters of the motorcycle engine designed in this embodiment are as follows: engine displacement (working volume). =125cc=125000mm 3 Rated power 5.5Kw, compression ratio ε=8, number of pistons n=1 (single-cylinder engine).

[0036] According to the definition of compression ratio, compression ratio ε is the ratio of the total cylinder volume to the combustion chamber volume, that is: (1); In the formula: — Combustion chamber volume (mm) 3 ) Engine working volume (mm) 3 ) From equation (1), the formula for calculating the combustion chamber volume can be derived: (2); Known parameters =125000mm 3 , Substituting 8 into equation (2), we get:

[0037] 2. Calculation of key parameters for cylinder and piston Based on the general design specifications for 125cc motorcycle engines, a cylinder diameter D=55mm is selected. According to the definition of engine displacement, the displacement... The cylinder volume swept by the piston as it moves from top dead center to bottom dead center is calculated using the following formula: (3); In the formula: D is the cylinder diameter (mm); S is the piston stroke (mm); n is the number of cylinders.

[0038] The formula for calculating the piston stroke S can be derived from equation (3): (4); Will =125000mm 3 Substituting D=55mm and n=1 into equation (4), we get: ; To verify the accuracy of the above parameters, D=55mm and S=52.6mm were substituted into equation (3) to verify the working volume: ; The verification results show that the calculated cylinder diameter and piston stroke parameters meet the working volume requirements of a 125cc engine.

[0039] Based on the cylinder diameter parameters, the diameter of the rotary valve shaft is determined to be d=0.85D (referring to the design experience of similar engines), and the calculated result is: d=0.85×55≈47mm; Selecting the opening length of the rotary valve as L=0.8D, we calculate: L=0.8×55=44mm.

[0040] 3. Calculation of Combustion Chamber Core Dimensions The combustion chamber width B was determined to be 33 mm using right-angled triangle calculations and analysis. The total combustion chamber volume... Combustion chamber volume from the cylinder head and piston top clearance combustion chamber volume It consists of two parts, namely: (5); Where: V_cylinder_head — combustion chamber volume of the cylinder head portion (mm) 3 V-top clearance — piston top clearance combustion chamber volume (mm) 3 ); — Piston groove volume (mm) 3 ).

[0041] (1) Calculation of combustion chamber volume in cylinder head section The combustion chamber in the cylinder head can be simplified as a structural model of "a cuboid minus the volume outside the chord," and its volume calculation formula is as follows: (6); In the formula: B—combustion chamber width (mm); L—combustion chamber length (mm); H—combustion chamber height (mm); R—rotary valve radius (mm), R=d / 2=47 / 2=23.5mm; θ—central angle corresponding to the chord (°), in this design θ=90° Substituting the known parameters into equation (6) and simplifying, we get: (7) (2) Calculation of piston top clearance combustion chamber volume The combustion chamber of a rotary valve engine consists of three parts: the combustion volume in the cylinder head, the combustion volume in the piston top clearance, and the combustion volume in the piston groove.

[0042] The piston top clearance combustion chamber volume can be calculated using the formula for the volume of a cylinder, taking the top clearance height h_clearance = 1mm (referencing design experience of similar engines). The calculation formula is as follows: (8); Substituting D=55mm and h_gap=1mm into equation (8), we get: ; The piston recess volume calculation shows that the piston recess has a crescent-shaped notch. The purpose of this design is to increase the combustion volume of the combustion chamber, while also reserving working space for the fuel injector and spark plug.

[0043] The piston's outer radius R is 27.5mm, and the angle of the sector's center is... The angle is 62.68°, the distance from the auxiliary line L is 28mm, substituting into the formula, the area of ​​the left semi-circle of the outer shape, the area of ​​the right semi-circle of the groove, the radius of the sector r is 18mm, the central angle of the sector n is 102.92°, the distance from the auxiliary line L is 28mm, substituting into the formula, the area of ​​the right semi-circle of the outer shape is:

[0044]

[0045] (9); (3) Determining the height of the combustion chamber Calculate the formula =2374.63 , =17857mm 3 , Substituting into equation (5), we get: ; Solving the above equation, we get: .

[0046] Based on the requirements of machining process, the combustion chamber height is rounded to H=13mm.

[0047] 4. Air inlet throughput capacity Engine intake and exhaust performance is directly measured by the port flow capacity, which profoundly affects charging efficiency and power output. The effective flow capacity of the port can be visually reflected by its angular surface value, defined as the integral of the port opening area over the crankshaft angle. This embodiment calculates the angular surface values ​​for rotary valves and valve-type structures separately, fully validating the flow capacity advantage of rotary valves.

[0048] (1) Gas timing design The rotary valve's intake and exhaust groove has a 125° center angle to match the intake and exhaust durations and ensure a complete scavenging process. The angle between the upper side of the intake and exhaust passages on the cylinder head and the center of the bore is 129°, ensuring that the intake and exhaust on the upper side of the rotary valve will not be short-circuited at top dead center of compression. The center angles of the intake and exhaust passage openings on the cylinder head are each 57.5°, determined by the requirements of port opening length and flow area. The combustion chamber side passage opening has a 95° center angle to balance the flow efficiency of intake and exhaust. The center angles of the isolation shores between the intake and combustion chambers, and between the exhaust and combustion chambers, are both 10°, ensuring the installation and isolation strength of the sealing strips.

[0049] Therefore, the intake and exhaust angles are equal. =2×(2×57.5°)=230°CA.

[0050] The exhaust advance opening angle and intake delay closing angle are both 40°CA, which effectively reduces the power stroke loss caused by an excessively large exhaust advance angle. Simultaneously, compared to an excessively large intake delay closing angle, it can also increase the engine's actual compression ratio, improving engine efficiency. The valve overlap angle is 20°CA, which fully utilizes the inertia of intake and exhaust to expel exhaust gases from the cylinder, reducing the residual exhaust gas coefficient. Since there are no reciprocating valves, there is no need to worry about excessive valve overlap angle causing interference between the valve and piston. Because the groove contains some fresh gas and the excessive valve overlap angle may cause short-circuit losses during scavenging, this single-rotary valve structure is suitable for direct injection engines but not for port injection engines.

[0051] (2) Basic definition of angle face value If we consider the moment the air inlet opens, when the crankshaft angle is... At that time, the instantaneous opening area of ​​the air vent is Then from the opening of the air inlet to that crankshaft rotation angle angular face value It can be calculated using the following integral formula: (10); Integrating the entire cycle from full opening to full closing of the vent, the result is the total angular surface area of ​​the vent. The larger the angular surface area, the larger the effective flow area of ​​the vent during the opening cycle, and the stronger its throughput capacity.

[0052] (3) Calculation of the angle surface value of the rotary valve Based on the core engine parameters determined in this embodiment: cylinder diameter D = 55mm, rotary valve shaft diameter d = 0.85D = 46.75mm (rounded to 47mm). The angular surface value of the rotary valve is the integral of the port opening area over the opening angle, and its instantaneous opening area is the product of the port opening chord length and the opening length.

[0053] Compared with the original engine, the valve timing of this design is the same as that of the original engine. The valve timing of the original engine is 230°CA during the intake process. Therefore, the intake angle of this design is β=230 / 2 / 2=57.5°.

[0054] The relationship between the various angles of the airway is 2β+2γ+2σ+φ+α=360; In the formula, γ is the compression top dead center, the angle between the air passage on the cylinder head and the semi-circular groove, which is generally greater than 2° to avoid short circuits.

[0055] In the formula, σ represents the rotary valve angle corresponding to the sealing strip and the mounting groove. Generally, from a safety and reliability perspective, the sealing strip width should be greater than 2mm, and each side of the groove should be no less than 2mm, i.e., 8mm. In this design, with a rotary valve diameter of 47mm, the corresponding angle is greater than 10°.

[0056] 2β+σ=φ=α+2σ+2λ; In the formula, λ is the single-sided angle of the rotary valve corresponding to the valve overlap angle. Generally, the valve overlap angle is 10-30° crankshaft angle. In this embodiment, the median value of 20° is taken, which corresponds to 10° of the rotary valve, and the single-sided angle is taken as λ=5°.

[0057] Solving for γ, we get γ + σ = 12.5°. Taking σ = 10°, we get γ + σ = 12.5°. Obtain γ=2.5°; α=95°; φ=125° For a cylinder head combustion chamber width corresponding to 90°, the calculation yields: 47 / 1.414=33mm. Based on the cylinder diameter of 55mm, the length of the inscribed rectangular air port is calculated to be 44mm. Assume the rotary valve opens at half-cycle angle =57.5°, corresponding to a crankshaft rotation angle of 115°, the radius of the rotary valve shaft R=d / 2=47 / 2=23.5mm. Combining the basic formula for angular facet value, the formula for calculating the angular facet value of the rotary valve is derived as follows: (11); With R=23.5mm and L=44mm, Substituting 57.5° into the above formula, we get:

[0058] In the formula — Rotary valve shaft radius (mm); L — Air port opening length (mm); — Rotary valve opening half-cycle angle (°).

[0059] (4) Calculation of valve structure angle surface value To compare and verify the air passage capacity of the rotary valve, a typical four-valve engine structure was selected as a benchmark for angular surface value calculation, referencing the dimensions of the original prototype. In the initial valve opening phase, the air passage area is controlled by the lateral area of ​​the frustum formed between the valve back cone and the valve seat. The key parameters at the valves of the original engine are as follows: diameter of each intake valve section... =22mm, valve seat inner diameter =19mm, valve stem diameter =5mm, valve back cone angle =45°, maximum valve lift =7mm.

[0060] 1) Determination of critical lift and fixed throat area There is a critical lift. When the valve lift reaches At the critical point, the area of ​​the frustum-shaped outer cone formed by the valve back cone and the valve seat is equal to the fixed throat area S. If the lift continues to increase, the airway flow area will remain unchanged at the fixed throat area S. The fixed throat area S and the critical lift need to be determined through calculation first. .

[0061] The fixed area of ​​the valve orifice is the annular area between the inner diameter of the valve seat and the diameter of the valve stem, and the calculation formula is as follows: (12); Will =19mm Substituting 5mm into equation (12), we get:

[0062] The critical lift is determined by the condition that the area of ​​the outer cone surface of the frustum is equal to the fixed area of ​​the throat. The formula for the area of ​​the outer cone surface of the frustum is as follows: (13); In the formula —Valve seat inner diameter (mm); — Critical lift (mm); γ — Valve back cone angle (°).

[0063] With S=263.89mm 2 , Substituting =19mm and γ=45° into equation (3-12), we get: ; Solving the above equation yields the critical lift. ≈13.255mm. This exceeds the valve lift; therefore, this engine does not have a critical point.

[0064] 2) Valve lift equation and Segmentation Based on the engine valve timing design, the total crankshaft angle during valve opening is... Based on general design parameters, the intake advance angle is selected. =15°CA, intake late closing angle =35°CA, therefore: With the valve opening start point as 0° and the midpoint of opening (maximum lift) as 115°CA (corresponding to maximum lift),... =7mm), the equation for the change of valve lift with crankshaft angle is fitted with a sine function, that is: (14); Substitution =7mm =230°, therefore:

[0065] 3) Valve structure angle surface value calculation (15); The integral is (0≤ ≤115°CA) Lift equation Substituting into the formula for the area of ​​the outer surface of a frustum, we get expression:

[0066] Substitution =19mm, γ=45° Simplifying, we get: ; Integrating this expression within the range of 0~115°CA (since the ascent and descent are symmetrical, the integral is taken as half the angle, the result is multiplied by 2, and then multiplied by 2 again for both intake valves), we get:

[0067] (5) Comparative analysis of air inlet throughput capacity The angular surface values ​​of rotary valves and valve-type structures were compared and calculated: the calculated angular surface value of the rotary valve was 2035mm. 2 CA, the traditional valve mechanism is calculated to be 1813.84mm. 2 CA, the former is increased to 1.12 times that of the latter. It can be seen that the rotary valve has a better angular surface value, and the effective flow area and air passage capacity during the opening cycle are significantly enhanced, resulting in a substantial increase in engine intake volume, and effective improvement in charging efficiency and power performance. The rationality of using a rotary valve structure in this embodiment is fully verified. (6) Fin heat dissipation design A significant amount of heat is generated during engine operation. If this heat cannot be dissipated in time, the cylinder block temperature will continuously rise, affecting power, reliability, and service life. Heat dissipation efficiency is directly determined by the fin structure, making the fins the core component of the cooling system. This embodiment determines the fin form based on literature, completes parameter design and heat dissipation verification through thermal calculations, and fully meets the heat dissipation requirements of the 125cc engine.

[0068] (7) Determination of fin structure Considering the power, operating conditions, and lightweight requirements of a 125cc engine, this embodiment designs the cylinder head cooling fins as an elliptical structure, as shown below. Figure 3 As shown, aluminum alloy is selected as the material, with a wall thickness of δ=5mm, so that heat dissipation efficiency and structural strength are taken into account at the same time.

[0069] (8) Calculation of basic thermal parameters and heat flux density Based on the actual operating conditions of a 125cc motorcycle engine, the basic parameters for heat dissipation calculation are determined as follows: cylinder wall temperature. Ambient air temperature Aluminum alloy thermal conductivity fin wall thickness

[0070] 1) Temperature difference calculation Temperature difference between cylinder block and ambient air for: (16); 2) Calculation of heat flux density According to Fourier's law, the heat flux density q through the cylinder wall can be expressed as: (17); Where: k is the thermal conductivity of the fin material (W / (m·K)); δ represents the temperature difference (K); δ represents the fin wall thickness (m). The negative sign in the formula indicates that the direction of heat transfer is opposite to the direction of the temperature gradient. In engineering calculations, its absolute value can be considered.

[0071] Given k=200W / (m·K), Substituting =185K and δ=0.005m into equation (17), we get: (Take the absolute value as 74000W / m) 2 ) 3) Calculation of convective heat transfer coefficient The relationship between heat flux density and convective heat transfer coefficient satisfies Newton's law of cooling: (18); Where: h is the convective heat transfer coefficient (W / (m²)). 2 ·K)) From equation (18), the formula for calculating the convective heat transfer coefficient h can be derived:

[0072] q=74000 W / m 2 , Substituting =185K, we get: ; (9) Calculation of fin efficiency Fin efficiency It is a key indicator for measuring the heat dissipation performance of fins, reflecting the ratio of actual heat dissipation to the ideal maximum heat dissipation. For straight fins with a constant cross-section, its efficiency formula is: (19); Where m is the thermal conductivity-convection characteristic parameter of the fin ( H is the average distance (m) from the outer wall of the base tube to the edge of the fin.

[0073] 1) Calculation of characteristic parameter m The formula for calculating the characteristic parameter m is: (20); h = 40W / (m) 2 Substituting k=200W / (m·K) and δ=0.005m into equation (20), we get: ; 2) Calculation of average distance H The formula for calculating the average distance H from the outer wall of the base tube to the edge of the fins is: (twenty one); In the formula: a is the semi-major axis of the elliptical fin (m); The outer diameter of the base tube is (mm).

[0074] outer diameter of base tube The equivalent circle circumference is calculated from the perimeter of the rectangle. Given that the rectangle's dimensions are 100mm × 118mm, the equivalent circle circumference is... mm, according to the circumference of a circle We can obtain: ; Combining the design parameters of the elliptical fin, taking the major semi-axis a=238mm and db≈138.8mm and substituting them into the calculation formula of (21), we get: ; 3) Fin efficiency calculate m 8.944 H Substituting 0.0843m into equation (3-19), we get: ; The calculation results show that the efficiency of the elliptical fin is 0.861, which means that the actual heat dissipation can reach 86.1% of the ideal maximum heat dissipation, indicating that it has good heat dissipation performance.

[0075] (10) Calculation and verification of total heat dissipation 1) Maximum heat dissipation calculate Maximum heat dissipation refers to the heat dissipation when the entire surface of the fins reaches the cylinder wall temperature. The calculation formula is: (twenty two); In the formula: The surface area of ​​the fins on both sides (m²) 2 ); The formula for calculating the surface area of ​​an elliptical fin is: (Area of ​​both sides), where b is the minor semi-axis of the elliptical fin. Taking the design parameters as b = 172mm = 0.172m and a = 238mm = 0.238m, substituting them, we get: ; h = 40 W / (m 2 ·K), 0.2572 m 2 , Substituting into equation (22), we get: ; 2) Calculation of actual total heat dissipation Q The actual total heat dissipation is the product of the fin efficiency and the maximum heat dissipation, that is: (twenty three); Will , Substituting into (23), we get: ; 3) Heat dissipation performance verification Based on the thermal load characteristics of a 125cc motorcycle engine, its heat dissipation requirement under rated operating conditions is approximately 1000~1200W. The total heat dissipation of the elliptical fins designed in this embodiment is approximately 1638.72W, which can meet the engine's heat dissipation requirements and verifies the rationality of the fin structure design.

[0076] (11) Selection of needle roller bearings The stability, reliability, and service life of the transmission system are directly determined by the needle roller bearing, which is the core support component of the rotating valve shaft. In this chapter, considering parameters such as working load, rotational speed, and temperature, the basic dynamic load rating required for the bearing is determined through theoretical calculations. Model selection is carried out based on the high-temperature environment, and life verification is performed to ensure a reasonable selection.

[0077] 1) Determination of basic parameters for model selection Combining the core parameters and working conditions of the 125cc motorcycle engine in this design, the basic parameters for selecting the needle roller bearing are determined as follows: (a) Engine core parameters: Rated power = 5.5kW = 5500W, medium to high rotational speed n = 6000 - 8000 rpm (n = 6000 rpm is taken for the selection calculation, and the value is based on typical working conditions); (b) Gas pressure parameters: Instantaneous maximum gas pressure in the combustion chamber P = 1.2 MPa (under medium to high rotational speed conditions, the gas pressure range is 0.8 - 1.2 MPa. To ensure the safety of model selection, the maximum value is taken according to the most severe working condition); (c) Structural dimension parameters: Piston diameter D = 55 mm (the diameter of the force-bearing surface of the rotating valve is the same as the cylinder diameter), module of the driving gear m = 2, number of teeth z = 34, pressure angle α = 20°; (d) Life and working condition coefficients: Designed service life = 10 4 h (failure probability ≤ 10%, meeting the conventional design requirements for motorcycle engine bearings); There is medium impact during engine operation, and the load coefficient = 1.4 is taken; The working temperature ≤ 250 °C. Checking the mechanical design manual, the temperature coefficient = 0.75 (standard value of the temperature coefficient for ordinary bearings when the temperature is 200 °C < T ≤ 250 °C); (e) Transmission efficiency: The rotating valve shaft adopts gear transmission, and the conventional gear transmission efficiency = 0.98.

[0078] 2) Calculation of key loads (a) Calculation of the force exerted by the combustion chamber gas on the rotating valve The force F exerted by the combustion chamber gas on the rotating valve is determined by the product of the gas pressure and the force-bearing area. The formula is: (24); P is the instantaneous maximum gas pressure in the combustion chamber (Pa); S is the force-bearing area of the rotating valve (m 2 ), that is, the cross-sectional area of the cylinder (the same as the force-bearing area of the piston top surface); The calculation formula for the force-bearing area S of the rotating valve is: (25); Substituting D=55mm=0.055m into equation (3-25), we get: ; P = 1.2 MPa = 1.2 × 10 6 Pa、 Substituting into equation (24), we get: ; (b) Calculation of rotary valve shaft torque and total radial load Calculation of power and torque of rotary valve shaft The input power of the rotary valve shaft is the product of the engine's rated power and the transmission efficiency, that is: (26); in, The engine's rated power (W); For transmission efficiency; Will =5500W Substituting 0.98 into the equation, we get: ; Based on the relationship between power and torque: The torque calculation formula can be derived as follows: (27); ω is the angular velocity of the rotary valve shaft (rad / s); the relationship between angular velocity and rotational speed is: (n is the rotational speed, r / min).

[0079] Substituting n=6000rpm into the angular velocity formula, we get: ≈628.32 rad / s Substituting P=5390W and ω≈628.32 rad / s into equation (27), we get: ; 3) Calculation of gear forces The formula for calculating the pitch circle diameter d of the drive gear is: (28); Substituting m=2 and z=34, we get: ; During gear transmission, the radial force of the driving gear on the driven gear (rotary valve shaft gear) With circumferential force The calculation formulas are as follows: (29); (30); Substituting T=8.58 N·m, d=0.068 m, and α=20° (tan20°≈0.3640), we get: ; .

[0080] 4) Calculation of total radial load The total radial load Fr on the rotary valve bearing is a vector sum of the gear radial force Fr2, the radial component of the gas force F, and the gear circumferential force Ft. Since the gas force F is perpendicular to the radial direction of the rotary valve shaft, the actual radial load is a combination of Fr2 and Ft, and the formula is modified as follows: (31); Will =91.8N Substituting 252.35N into the equation, we get: ; Considering the additional loads during engine operation (such as vibration, impact fluctuations, etc.), the total radial load is taken in engineering. =300N (with an 11.7% safety margin based on the calculated value).

[0081] 3. Calculation of equivalent dynamic load and basic rated dynamic load (1) Calculation of equivalent dynamic load For needle roller bearings that primarily bear radial loads, the formula for calculating the equivalent dynamic load P is: (32); In the formula: —Load factor, which reflects the effect of impact load on the bearing.

[0082] Will =1.4、 Substituting 300N into (32) yields: ; (2) Calculation of basic rated dynamic load According to GB / T 6391-2010, the formula for the basic rated life of rolling bearings is: (33); C represents the basic rated life (h); C represents the basic rated dynamic load (N). Temperature coefficient Life index (needle roller bearing life index) = (Complies with standard requirements) Will =10 4 h, n=6000rpm =0.75, P=420N = Substituting into equation (33), the calculation formula for the basic rated dynamic load C is derived: ; Substitute data for calculation .

[0083] 4. Selection and Verification of Needle Roller Bearing Model (1) Model selection Considering the high-temperature operating conditions of the engine (≤250℃), high-temperature adaptable cage-free needle roller bearings (RNA series, which has a compact structure and is suitable for installation scenarios with smaller shaft diameters) are preferred. The RNA6908 needle roller bearing, which meets the basic dynamic load rating requirements, was selected. Its key parameters are as follows: inner diameter d=40mm, outer diameter D=52mm, width B=12mm, and basic dynamic load rating C=24.5kN.

[0084] Since the basic rated dynamic load C=24.5kN of the RNA6908 bearing is greater than the calculated 23.7kN, and its dimensions match the installation space of the rotary valve shaft, the RNA6908 needle roller bearing is selected.

[0085] (2) Lifetime verification Substituting the basic rated dynamic load C = 24.5 kN = 24500 N of the selected bearing into the basic rated life formula (33), we can verify whether its service life meets the design requirements. ; Verification results show that the actual service life of the selected RNA6908 needle roller bearing is much greater than the design requirement of 10 years. 4 h is sufficient to meet the support requirements of the rotary valve shaft, and the selection is reasonable and reliable.

[0086] 5. Design of the rotary valve shaft For a 125cc single-cylinder rotary valve engine (compression ratio ε=8), rated power Based on the theory of internal combustion engine operation, the parameters for intake, compression, combustion, and exhaust processes were calculated, and the strength of the rotary valve shaft was checked. The calculation results can provide a theoretical basis for the structural design and performance optimization of this type of engine.

[0087] The following are some data points for the 125cc engine used in this embodiment: cylinder bore D = 55mm; speed n = 6000r / min; working volume =125000 Compression ratio ε=8; Atmospheric state =1 bar、 =288K; Low calorific value of fuel =43900KJ / kg; Excess air coefficient α=0.88; Heat utilization coefficient =0.88; Residual exhaust gas coefficient γ=0.075; Exhaust terminal temperature Tr=1050K; Indicator diagram fullness coefficient =0.95; mechanical efficiency =0.91; mean polyvariable compression index =1.20; Intake air heating temperature rise =18℃.

[0088] (1) Calculation of exhaust process The back pressure during the exhaust process is obtained by correcting for atmospheric pressure, and the calculation formula is as follows: (34); This refers to the exhaust back pressure (bar). This is the exhaust back pressure correction coefficient, with a value of 1.08 (adaptation value for exhaust resistance of small displacement engines). Atmospheric pressure (bar); Substitute the parameters into the formula: ; (2) Calculation of intake process (a) The intake end temperature is affected by the ambient temperature, the intake heating temperature rise, and the residual exhaust gas temperature. The calculation formula is as follows: (35); The intake end temperature (K); Atmospheric temperature (K); γ represents the intake air heating temperature rise (°C); γ represents the residual exhaust gas coefficient. The residual exhaust gas temperature is set to 1020K (the appropriate exhaust temperature value for small displacement engines).

[0089] Substitute parameters to calculate: ; (b) Inflation efficiency calculation Intake efficiency is a core indicator for evaluating an engine's intake capacity, and its calculation formula is as follows: (36); For inflation efficiency; This refers to the compression ratio; The intake pressure is set to 0.82 bar (adapted to the intake resistance of small displacement engines).

[0090] The formula for calculating clearance volume is:

[0091] In the formula: The clearance volume is (cc). The cylinder working volume (cc).

[0092] Substituting into the above formula, we get: Clearance volume calculation ; Inflation efficiency calculation: ; (c) Calculation of the compression process The compression process follows the laws of polytropic processes, and the formulas for calculating the final pressure and temperature are as follows: ; (37); The final pressure (bar) for compression; The final temperature of compression (K); The average polytropic compression index.

[0093] Substituting the above calculation results into the formula, we obtain the final compression pressure:

[0094] Compression endpoint temperature: (296℃) (d) Combustion process calculation 1) The final mixture at the compression endpoint consists of fresh air and residual exhaust gas. The formula for calculating the average isochoric specific heat capacity is as follows: (38); The average isochoric specific heat capacity of the mixture ( ) The specific heat capacity is equal to that of fresh air. The conclusion is The conversion unit is 0.72. ; The isochoric specific heat capacity of the residual exhaust gas is given by a = 0.8 (the isochoric specific heat capacity of the residual exhaust gas is 0.8 times that of the fresh air). This represents the residual exhaust gas coefficient.

[0095] Substitute the calculated data above into the formula:

[0096] Since the average molar specific heat capacity of the mixture is usually within Within the acceptable range, it meets the requirements.

[0097] 2) Calculation of combustion endpoint pressure The final combustion pressure is obtained by multiplying the pressure rise ratio by the final compression pressure, and the calculation formula is as follows:

[0098] (39); The final pressure of combustion (bar); The pressure rise ratio; The numerator is the change factor, with a value of 1.06 (adapted to small-displacement gasoline engines). The combustion endpoint temperature is approximately 2200~2400K, with a value of 2293K (2020℃). Substituting the above results into the formula, we get: Pressure rise ratio: ; End-of-combustion pressure: .

[0099] (6) Strength check of rotary valve shaft (a) The rotary valve bearing is subjected to combustion pressure, and the force calculation formula is as follows: (40); The axial force (N) acting on the valve bearing; The final pressure of combustion (1 bar = S represents the flow area of ​​the air valve, and its value is... (125cc engine compatibility value); Substitute the calculation result into the formula: ; (b) Calculation of minimum allowable diameter of valve shaft The valve shaft is simplified as a simply supported beam, and the formulas for calculating the bending moment at the critical section and the minimum allowable diameter are as follows: and (41); 1 is the maximum bending moment at the critical section (N·m); l is the valve shaft support span, taken as 0.048m (suitable for 125cc engines); D is the minimum allowable diameter of the valve shaft (m). For the allowable stress of the valve shaft material, the value for mold steel is 160× .

[0100] Substituting the above results into the equation, we get: Maximum bending moment at the critical section:

[0101] Minimum allowable diameter Therefore, the shaft diameter of the force-bearing part of the rotary valve shaft must not be less than 15mm.

[0102] The parameters of the entire working process of a 125cc single-cylinder rotary valve engine were calculated, and the key thermodynamic parameters of the intake, compression, combustion and exhaust processes were determined, providing basic data for engine performance simulation.

[0103] The strength verification results of the rotary valve shaft show that the strength requirements under rated working conditions can be met when the shaft diameter is not less than 15mm, which provides a theoretical basis for the structural design of the valve shaft.

[0104] 6. Design of sealing rings and sealing strips The reliable operation of an engine is directly guaranteed by its sealing system, whose structure must be highly compatible with the valve train. Rotary valve engines have a compact cylinder head structure, with the intake and exhaust ports close to the combustion chamber. Traditional rubber seals cannot withstand high-temperature conditions, and seal failure can lead to cylinder pressure drop and gas leakage. Therefore, this chapter designs an axial-circumferential composite sealing mechanism to effectively isolate the intake and exhaust ports from the combustion chamber.

[0105] (1) Axial sealing system When the rotary valve is working, combustible gas or exhaust gas can easily move axially along the valve shaft, causing insufficient cylinder pressure and accelerating bearing wear. This design adopts a double-layer elastic open sealing ring structure: the sealing ring is assembled in the ring groove at both ends of the valve shaft, relying on its own elasticity to achieve initial sealing; the ring and the groove are clearance-fitted, the sealing ring does not rotate with the shaft, but can move slightly with the pressure difference in the cylinder, and further tightens against the groove wall through the gas back pressure to strengthen the seal.

[0106] The openings of the two sealing rings are staggered by 180° to form a labyrinth seal structure, effectively preventing leakage from a single ring opening. At the same time, a concave-convex locking mechanism is designed on the side wall of the rings. A groove with a central angle of 15° and a depth of 0.6mm is machined on sealing ring A, and a protrusion with a central angle of 14° and a height of 0.5mm is provided at the corresponding position on sealing ring B. This restricts the sliding of the sealing rings, keeps the opening misaligned state, and eliminates the problem of seal failure.

[0107] (2) Circumferential sealing system The gap between the rotary valve shaft and the shaft groove can easily cause gas to move around circumferentially, leading to cylinder pressure loss. This design incorporates two sealing strips with shaped spring plates on the spacer between the intake and exhaust ports and the combustion chamber. The sealing strips and mounting grooves are fitted with a clearance fit, and the spring plates provide preload for initial positioning. During the compression and power strokes, high-pressure gas from the combustion chamber enters the back gap of the sealing strips, using air pressure to press the sealing strips tightly against the valve shaft surface, forming the main sealing force. This structure relies on air pressure to enhance the seal under high-seal-demand conditions such as compression and power strokes, while automatically reducing the clamping force under low-seal-demand conditions, thereby reducing shaft friction and improving mechanical efficiency.

[0108] A 2mm rectangular guide slider is added to both ends of the sealing strip to prevent the sealing strip from rolling sideways and jamming the valve shaft, and to limit the centering position of the irregular spring sheet, ensuring the stability of the sealing strip support point.

[0109] Example 3 The present invention further provides a specific embodiment of finite element analysis of the static characteristics of the rotary valve in Example 1: The rotary valve shaft is a core component in the strength research of the cylinder head of a rotary valve motorcycle engine. It operates in the harshest environment and has relatively weak structural strength; its mechanical properties and thermal deformation directly determine the engine's reliability. Therefore, static characteristic finite element analysis of it has significant engineering value.

[0110] This embodiment utilizes finite element analysis software to focus on analyzing static and thermal expansion characteristics. By calculating the deformation results of components under load and temperature, it provides a precise basis for the design of the clearance between the rotary valve shaft and the shaft groove, ensuring that the valve shaft does not bend or deform during operation, nor does it experience thermal expansion interference, thus avoiding jamming and ensuring stable engine operation.

[0111] (1) Overview of Finite Element Analysis Finite element analysis (FEM) breaks down a continuous research object into a finite number of interconnected micro-units. By analyzing the mechanical properties of each unit, the mechanical behavior of the overall structure can be equivalently reflected. This method integrates theories from multiple disciplines and is widely used in mechanical engineering. It can efficiently complete strength analysis and structural optimization, significantly shortening the experimental cycle and reducing research and development costs.

[0112] To meet the requirements of static and thermal analysis, the finite element analysis process is summarized into seven core steps: ① Discretize the rotary valve shaft model into tiny elements, construct an equivalent model through nodes, and apply loads to the nodes; ② Select a suitable displacement mode and use nodal parameters to describe the displacement, stress, and strain relationships of the elements; ③ Analyze the mechanical properties of the elements; ④ Solve for the equivalent nodal forces based on the principle of virtual work; ⑤ Construct the equilibrium equations of the overall structure; ⑥ Apply displacement boundary constraints; ⑦ Calculate the stress and deformation of each element node.

[0113] (2) Brief introduction to finite element software This embodiment uses the mainstream finite element analysis software ANSYS to carry out relevant simulations. This software is powerful and has rich interfaces. It is compatible with 3D modeling software such as CATIA and UG, supports the direct import of common format models, and its built-in 3D modeling module can realize the rapid modification and simplification of models to adapt to engineering analysis needs.

[0114] This study utilizes ANSYS Workbench to conduct static and thermal analyses. This module excels in static and thermo-coupling simulations. The entire analysis process is divided into three parts: pre-processing, solving, and post-processing. (1) Preprocessing covers model processing and mesh generation. The model is simplified by using the DM module to remove details such as fillets and small holes, which facilitates the application of loads and improves computational convergence. Mesh accuracy is controlled by relevant parameters, and a balance needs to be struck between computational accuracy and efficiency. The finer the mesh, the more realistic the result, but the computation time also increases.

[0115] (2) The calculation stage focuses on defining constraints and applying loads. The software supports various constraint forms such as fixed constraints and cylindrical constraints, and can also apply various loads such as concentrated forces, pressure, and temperature. It is precisely set according to the actual working conditions of the valve shaft to ensure the reliability of the analysis results.

[0116] (3) Post-processing visualizes the results through cloud maps, data tables, etc., clearly showing the deformation and stress distribution of the valve shaft under static and thermal action, providing data support for structural optimization and clearance design.

[0117] (3) Stress analysis of rotary valve shaft First, the load and temperature conditions during the operation of the rotary valve shaft are analyzed to clarify the boundary conditions: the rotary valve shaft mainly bears the maximum combustion pressure generated by the explosion of combustible gas in the combustion chamber, and the two ends are supported by bearing seats. Under this combined load, it is prone to bending deformation. At the same time, the working temperature in the cylinder head changes by about 300°C, and the valve shaft will bear the thermal stress generated by the temperature load, so thermo-mechanical coupling analysis needs to be carried out.

[0118] In this embodiment, the rotary valve shaft does not bear any additional load during rotation; the torque and power are provided by the crankshaft, and the shaft is only subjected to the frictional resistance torque from the sealing strip. This frictional resistance torque is extremely small and has almost no impact on the strength of the rotary valve shaft. Therefore, in the subsequent static and thermal analyses, the torque effect is temporarily ignored, and the focus is on studying the effects of pressure and temperature loads. By simplifying the calculation model, the efficiency and accuracy of the analysis are further improved.

[0119] (4) Process the rotary valve shaft model using ANSYS. After opening the working interface, the static structure under geometry is selected, entering the statics analysis module, where the pre-built 3D model of the rotary valve is imported. ANSYS only supports STP, .igs, and x_t formats, so the model must be exported as STP format from CATIA beforehand. Without affecting the simulation, the model is simplified; irrelevant parts such as sealing rings, sealing strips, gears, bearings, and bolts are removed, reducing the computational load and shortening the calculation time.

[0120] After importing the simplified 3D model into ANSYS, the relevant material properties were set by selecting engineering data. The material for the rotary valve shaft was heat-resistant alloy steel from the material library. Next, meshing was performed. Given the simple and regular structure of the rotary valve shaft, the ANSYS automatic meshing module was used, and the mesh size was selected in the mesh options to insert the mesh. By changing the element size, the minimum mesh parameter was adjusted; setting the element size to 5.0 mm yielded an average value of 0.63.

[0121] Generally, a mesh quality greater than 0.7 indicates excellent mesh quality; a quality between 0.3 and 0.7 indicates moderate mesh quality; and a quality less than 0.3 indicates poor mesh quality. Considering practical factors such as program computation time and computer hardware configuration, an average quality within the range of 0.3 to 0.7 is sufficient to meet the analysis accuracy requirements.

[0122] This parameter setting ensures sufficient reliability of the simulation results without reducing computational efficiency due to excessively fine meshing. After completing the relevant settings, click "Generate Mesh," and the system will automatically generate the mesh. The number of mesh nodes for the rotary valve is set to 16005, and the number of mesh elements is set to 8958.

[0123] (5) Constraints and load settings for the rotary valve shaft model (a) Constraints of the rotary valve shaft model The boundary conditions for finite element analysis must be set based on the actual working environment of the object under study. The rotary valve shaft is assembled inside the cylinder head and is supported by needle roller bearings at both ends. It has a large clearance fit with the valve shaft groove and no contact action. Therefore, the valve shaft is simplified as a simply supported beam subjected to a uniformly distributed load.

[0124] In the ANSYS interface, select the static structure and click Support. Choose Fixed Support, select the support surface, and then select the bearing mounting location. Click Apply to complete the support surface settings. The core function of Fixed Support is to prevent the selected geometric or mesh entity from moving or deforming, ensuring that the constraint state of the model during simulation matches the actual working scenario.

[0125] (b) Load on the rotary valve shaft model During the engine's compression and power strokes, the combustion chamber is sealed by the intake and exhaust valve shafts, and the high-temperature, high-pressure gas inside is subjected to an upward thrust on the rotating valve shaft. At the maximum combustion pressure during the power stroke, the stress and strain of the rotating valve shaft are pushed to their peak value, therefore the uniformly distributed load value is set at the maximum combustion pressure of 4.77 MPa.

[0126] The rotary valve shaft is almost unloaded during operation, and no torque is output; it is only subject to the frictional resistance of the sealing strip. The elasticity of the irregularly shaped spring is used to overcome the weight of the sealing strip, and the frictional force is considered negligible, so the torque effect is ignored. In addition, during the power stroke, the high-temperature and high-pressure gas is radiated to the valve shaft. Under extremely high-speed conditions, a temperature difference of 300°C on the inner surface of the shaft and 200°C at the shaft end is formed, and the thermal expansion and contraction of the metal causes geometric deformation, thus applying corresponding thermal conditions.

[0127] In ANSYS, click on the static structure insertion, select pressure, add a load, select the axial surface of the rotary valve bearing with a uniformly distributed load, and set the pressure value to 4.77 in the pressure details. (Ramp), the load application mode is a constant pressure in a single direction, applicable to the selected plane or curved surface (x, y, or z direction). Then click on the static structure insertion, select thermal conditions to add a temperature load, select the rotary valve shaft as the temperature application object, and set the temperature to 300°C (ramp) in the thermal condition details.

[0128] (6) Bending stress analysis and thermal expansion analysis After completing preprocessing operations such as model import, mesh generation, constraint setting, and load application, simulation analysis is performed using ANSYS. Select "Solve," click "Deformation," and choose "Total Deformation" to output the total deformation; click "Stress," and choose "Equivalent Stress." After setting, click "Solve" to start the calculation, which takes 1 second.

[0129] Simulation results show that the deformation of the rotary valve is caused by the combined effects of pressure load and temperature conditions, with thermal deformation being the primary factor and pressure load being secondary. When the cylinder temperature reaches approximately 300°C after engine combustion, thermal expansion caused by high temperature is the main source of deformation, while the compression of the valve end face by the combustion endpoint pressure of 47.67 bar further amplifies the mechanical deformation. To prevent interference between the rotary valve shaft and the valve shaft groove after bending deformation or thermal expansion, which could lead to valve shaft jamming or expansion seizure, a reasonable deformation margin needs to be reserved. Based on the simulation results, a large clearance fit is adopted between the rotary valve shaft groove and the rotary valve, and a large clearance fit is also adopted between the bearing groove and the bearing outer diameter, thus ensuring its operational reliability under high temperature and high pressure conditions. Compared with the designed reserved clearance, the deformation of 0.17 mm is less than the reserved clearance, and the structure still maintains sufficient safety margin after deformation, without interference with the cylinder head or valve seat. The clearance meets the design requirements.

[0130] However, the equivalent stress value is abnormally high, mainly due to unreasonable design. To improve the reasonableness of the results, optimization can be made at the simulation settings level: add rounded corners to the sharp corners of the model, and adjust the concentrated loads and constraints to surface loads and constraints; then refine the mesh of the stress surface to 3, making the calculated data more accurate. Additionally, the material of the rotary valve can be changed to enhance its yield strength, tensile strength, and other properties, thus better ensuring that the simulation results meet the design requirements.

[0131] After optimizing the load and boundary conditions of the simulation model and effectively handling stress singularities, the recalculated maximum equivalent stress was corrected to 425.48. Because this heat-resistant alloy steel has a yield strength of 800 kJ / m² at room temperature. (Values ​​explicitly stated in the national standard GB / T 1221 and the heat-resistant steel handbook). At 300℃, 95% of the strength is retained, therefore the yield strength is approximately 760 Nm. The results are within the range of the material's yield strength and match the distribution law of the total deformation, meeting the large clearance fit standard given in the design. They can truly reflect the mechanical response characteristics of the structure under this working condition, providing a reliable numerical basis for subsequent structural design and optimization.

[0132] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rotary valve cylinder head, characterized in that, include: Cylinder head (1), rotary valve (2), transmission mechanism and sealing system; The cylinder head (1) has a combustion chamber, an intake port, an exhaust port and an air port communicating with the combustion chamber. The intake port and the exhaust port are respectively located on both sides of the cylinder head (1), and the air port is located below the rotary valve (2). The rotary valve (2) is rotatably disposed inside the cylinder head (1) via a rotary valve shaft. A crescent-shaped groove is provided on the outer circumferential surface of the rotary valve (2). The crescent-shaped groove is configured such that when the rotary valve (2) rotates with the crankshaft of the engine at a predetermined timing, the crescent-shaped groove passes through the intake port, the exhaust port, and the air port in sequence to selectively open or close them, so as to realize the sequential control of the engine's exhaust, intake, compression, and power strokes. A timing drive mechanism is used to connect the crankshaft of the engine to the rotary valve shaft to achieve timing drive between the crankshaft of the engine and the rotary valve. A sealing system is provided between the cylinder head (1) and the rotary valve shaft to prevent gas leakage.

2. The rotary valve cylinder head according to claim 1, characterized in that, The outer surface of the cylinder head (1) is provided with heat dissipation fins, which are specifically elliptical cross-section structures.

3. The rotary valve cylinder head according to claim 1, characterized in that, The center angle of the crescent-shaped groove of the rotary valve (2) is 125°, and the angle between the upper edge of the intake and exhaust passages on the cylinder head and the center of the air port is 129°.

4. The rotary valve cylinder head according to claim 1, characterized in that, The rotary valve shaft is supported by a needle roller bearing, which is a cage-type bearing without an inner ring.

5. The rotary valve cylinder head according to claim 1, characterized in that, The diameter of the rotary valve shaft is 0.85 times the cylinder diameter, and the effective flow length of the crescent-shaped groove corresponding to the air port is 0.8 times the cylinder diameter.

6. The rotary valve cylinder head according to claim 1, characterized in that, The timing transmission mechanism includes: timing pulleys respectively disposed on the crankshaft of the engine and the rotary valve shaft, and a toothed belt connecting the timing pulleys, so as to realize a timing transmission with a transmission ratio of 2:1 between the crankshaft of the engine and the rotary valve shaft.

7. The rotary valve cylinder head according to claim 1, characterized in that, The sealing system includes: an axial sealing structure and a circumferential sealing structure; An axial sealing structure is provided at the axial gap between the two ends of the rotary valve shaft and the cylinder head (1); the shaft end sealing structure includes at least two elastic open sealing rings, the sealing rings are assembled in the annular groove of the rotary valve shaft and do not rotate with the rotary valve shaft, and the openings of adjacent two sealing rings are staggered to form a labyrinth sealing structure. A circumferential sealing structure is provided at the spacer between the air inlet, the exhaust outlet and the combustion chamber, including at least one sealing strip and an elastic element that provides pre-tightening force to the sealing strip. The sealing strip is configured to be pressed against the surface of the rotary valve shaft under the action of high-pressure gas in the combustion chamber.

8. The rotary valve cylinder head according to claim 7, characterized in that, The two adjacent sealing rings of the axial sealing structure are respectively provided with mutually cooperating concave-convex locking structures to restrict the relative sliding of the sealing rings and maintain the opening misalignment state.

9. The rotary valve cylinder head according to claim 7, characterized in that, The sealing strip is provided with guide sliders at both ends to prevent the sealing strip from rolling on the surface of the rotary valve shaft.

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