A six-cylinder four-valve engine exhaust system and exhaust pipe

Abstract

This invention discloses an exhaust system for a six-cylinder, four-valve engine, including a cylinder head and an exhaust pipe. The cylinder head contains coolant and has several cooling water passages. A guide edge is provided within the cylinder head, and guide holes are formed between the guide edge and the top and bottom surfaces of the cylinder head. A set of mounting holes is located above the guide holes on the front end face of the cylinder head. The exhaust pipe is fixed to the front end of the cylinder head through the mounting holes. The exhaust pipe has a segmented structure, and a sealing structure is provided at the joints of the segments. This invention eliminates dead zones in the coolant flow, improving coolant fluidity and preventing excessively high surface temperatures in the cylinder head's water passages. The installation of long bolts on the exhaust pipe, through control of positioning errors and fitting clearances, ensures that the bolts and holes do not interfere, preventing stress caused by interference and exhaust pipe breakage at high temperatures. The composition of the exhaust pipe has been improved, enhancing its high-temperature resistance.

Description

[Technical Field]

[0001] This invention belongs to the field of engine technology, specifically relating to an exhaust system and exhaust pipe for a six-cylinder four-valve engine. [Background Technology]

[0002] The function of the engine cooling system is to dissipate the heat absorbed by heated parts in a timely manner, ensuring that the engine operates at its optimal temperature. Engine cooling systems are divided into air-cooled and water-cooled systems. Cooling systems that use air as the cooling medium are called air-cooled systems; those that use coolant are called water-cooled systems. The role of the cooling system is to ensure that the engine operates at its optimal temperature under all operating conditions. The suitability of the cooling system directly affects the engine's lifespan and fuel economy. Therefore, in the design and calculation of the cooling system, the selection of the radiator and the matching of the fan play a crucial role.

[0003] Current six-cylinder, four-valve water-cooling systems have several problems during operation, negatively impacting engine performance and cooling efficiency. For example, the existing cylinder head structure, while internally filled with cooling water channels, suffers from bulges in the flow path due to the exhaust pipe mounting location. As the coolant flows over these bulges, a depression forms at the waist of the bulge, reducing coolant flow and creating dead zones. This prevents cooling in these areas. When the temperature of the cylinder head water jacket metal surface exceeds 100°C, it heats the coolant, causing it to vaporize above its boiling point. This vaporization gradually expands, leading to overheating of the engine cooling system and potentially causing cylinder scoring and other problems. Cylinder head gasket failure; the connection between the cylinder head and exhaust pipe requires good sealing at the joint, and the exhaust pipe must have high temperature resistance. However, after the exhaust pipe is installed, the exhaust temperature is extremely high when the engine is running. When the connection between the cylinder head and exhaust pipe expands due to high temperature, the bolt installation clearance of the exhaust pipe changes, causing interference. Under these circumstances, bolt breakage, loosening, and exhaust pipe seal failure are very likely to occur. Currently, there are combined exhaust pipes, which are usually sealed with sealing ropes at the connection during assembly. The traditional inner core expansion layer material is short fiber of 0.3-0.5mm. Under high temperature conditions, the outer layer is easily damaged and can be blown away by airflow, leading to seal failure. [Summary of the Invention]

[0004] The purpose of this invention is to provide an exhaust system and exhaust pipe for a six-cylinder, four-valve engine, to solve the problems of dead zones in the cylinder head that lead to poor water flow, increased liquid vaporization, and overheating of the engine cooling system, ultimately causing safety failures such as cylinder scoring or cylinder head gasket failure; the connection between the cylinder head and exhaust pipe, due to the difference in thermal expansion coefficients caused by high temperatures, is prone to bolt breakage, loosening, and seal failure under operating conditions; and the traditional sealing rope at the connection is easily damaged under high temperatures, leading to seal failure.

[0005] To solve the above technical problems, the present invention adopts the following technical solution:

[0006] An exhaust system for a six-cylinder, four-valve engine includes a cylinder head and an exhaust pipe. The cylinder head contains coolant and has several cooling water passages. A guide edge is provided within the cylinder head, and guide holes are formed between the guide edge and the top and bottom surfaces of the cylinder head. A set of mounting holes is provided on the front end face of the cylinder head, located above the guide holes. The exhaust pipe is fixed to the front end of the cylinder head through the mounting holes. The exhaust pipe has a segmented structure, and a sealing structure is provided at the joints of the segments.

[0007] Furthermore, the mounting hole group consists of bolt holes, distributed at four corners on the front end face of the cylinder head, with an exhaust hole in the center of the four corners of the mounting hole group, and the air inlet of the exhaust pipe is connected to the exhaust outlet of the cylinder head.

[0008] Furthermore, the number of mounting hole groups matches the number of exhaust outlets.

[0009] Furthermore, the exhaust pipe includes a central pipe and an exhaust branch pipe. The central pipe has a left air intake port and a right air intake port. The central pipe has several mounting holes, which are divided into holes A, B and C. Holes A and B are respectively located on the flange surfaces of the left air intake port and the right air intake port, and the rest are holes C. Holes A and B are located on the same transverse plane, and the positioning error of holes A and B in the transverse and longitudinal directions is less than 0.5.

[0010] Furthermore, the fitting clearance between the C holes is 1.

[0011] Furthermore, the outer surface of the intermediate tube is provided with several reinforcing ribs.

[0012] Furthermore, an exhaust pipe gasket is provided between the exhaust port of the cylinder head and the intake port of the exhaust pipe.

[0013] Furthermore, the sealing structure is a sealing rope, which consists of an outer high-temperature resistant braided rope protective layer and an inner core expansion layer. The high-temperature resistant braided rope protective layer is composed of Si+C, and the inner core expansion layer is composed of Al+O.

[0014] An exhaust pipe for a six-cylinder, four-valve engine exhaust system, wherein the exhaust pipe material is composed of the following components: C: 2.5-3.8%, Si: 3.5-4.9%, Mn: ≤0.4%, P: ≤0.07%, S: ≤0.06%, Mo: 0.4-0.9%, Cr: ≤0.5%, Ni: ≤0.6%, Cu: ≤0.7%, Ti: ≤0.4%, with the balance being molten iron.

[0015] The beneficial effects achieved by this invention are:

[0016] 1. The internal structure of the cylinder head and the connection structure between the cylinder head and the exhaust pipe are optimized. After changing the connection structure between the cylinder head and the exhaust pipe, the bolts inside the cylinder head can be eliminated. At the same time, it is conducive to the flow of coolant, eliminates the dead zone of water flow, and improves the fluidity of coolant. This prevents the surface temperature in the cylinder head water passage from exceeding 100°C, which can lead to coolant vaporization and gradual expansion, thereby causing the engine cooling system to overheat and causing cylinder scoring and head gasket failure.

[0017] 2. The installation of long bolts on the exhaust pipe is ensured by controlling the positioning error and the fitting clearance to ensure that the gap between the bolt and the hole is greater than 0 when the exhaust pipe expands at high temperature. This ensures that the bolt and the hole will not interfere with each other, so as to avoid stress caused by interference, which could lead to the exhaust pipe breaking at high temperature.

[0018] 3. The composition of the exhaust pipe has been improved, resulting in an exhaust pipe with good high-temperature resistance, capable of withstanding continuous high temperatures up to 680°C and instantaneous high temperatures up to 720°C, ensuring stable operation of the exhaust pipe under different working conditions.

[0019] 4. The exhaust pipe is wrapped with a heat-insulating metal cladding and soft cladding with a total thickness of 10, which keeps the temperature of the outer surface of the cladding below 150°C, effectively improving heat insulation and meeting the requirements for preventing burns and fire. By arranging reasonable reinforcing ribs, the fatigue strength safety factor is ensured to be greater than 1.5, thereby improving the strength and service life of the exhaust pipe.

[0020] 5. Double-layer full-wave 1Cr17Ni7 stainless steel exhaust pipe gasket, with a working line voltage greater than 10N / mm, ensuring sealed exhaust gas during operation and preventing performance degradation and cylinder head cover gasket burnout and oil leakage caused by high-temperature exhaust gas leakage.

[0021] 6. The structure of the sealing rope is optimized to a long fiber structure, with fiber lengths between 10 and 30 mm, woven to the required length. Even if the outer protective layer is damaged, the expansion core can maintain its shape, continuously withstand high temperatures ≥850°C, instantaneously withstand high temperatures ≥1000°C, and have a longitudinal tensile strength ≥250N, ensuring high-temperature sealing performance. [Attached Image Description]

[0022] In the attached diagram:

[0023] Figure 1 This is a partial 3D schematic diagram of an existing cylinder head;

[0024] Figure 2 This is a three-dimensional schematic diagram of the present invention;

[0025] Figure 3 This is the front view of the present invention;

[0026] Figure 4 yes Figure 3 A three-dimensional schematic diagram of the top view and cross-sectional view at point AA;

[0027] Figure 5 This is a sectional view of the main view of the present invention;

[0028] Figure 6 This is a rear perspective three-dimensional schematic diagram of the exhaust pipe of the present invention;

[0029] Figure 7 This is a sectional view of the exhaust pipe of the present invention from the rear view.

[0030] Figure 8 This is a rear view of the intermediate tube of the present invention;

[0031] Figure 9 This is a line graph showing the tensile strength of the exhaust pipe of the present invention at different temperatures;

[0032] Figure 10 This is a temperature field distribution cloud map of the exhaust pipe of the exhaust system of the present invention at a rated speed;

[0033] Figure 11 This is a temperature time history diagram of the highest temperature node in the exhaust system of the present invention.

[0034] Attached reference numerals: 1. Cylinder head; 1-1. Sand cleaning hole; 1-2. Mounting hole group; 1-3. Guide edge; 1-4. Guide hole; 1-5. Exhaust outlet; 2. Turbocharger assembly; 3. Exhaust pipe; 3-1. Intermediate pipe; 3-1-1. C hole; 3-1-2. A hole; 3-1-3. B hole; 3-2. Exhaust branch pipe; 4. Exhaust pipe gasket; 5. Heat insulation sleeve; 6. Long bolt; 7. Sealing rope.

Detailed Implementation Methods

[0035] The following is a detailed description with reference to specific embodiments.

[0036] The present invention will be further described in detail below with reference to specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0037] like Figure 1-11As shown, a six-cylinder, four-valve engine exhaust system includes a cylinder head 1 and an exhaust pipe 3. Coolant is contained within the cylinder head 1. The coolant flows from the bottom surface of the cylinder block through the water inlet of the cylinder head 1 and then enters the cylinder head 1. The cylinder head 1 has several cooling water passages for coolant flow. Several vertically spaced guide edges 1-3 are horizontally arranged within the cylinder head 1. Guide holes 1-4 are formed between the guide edges 1-3 and the top and bottom surfaces of the cylinder head 1. The cooperation of the guide edges 1-3 and the guide holes 1-4 allows the coolant to flow upwards and downwards after entering the cylinder head 1 from the water inlet, obstructed by the guide edges 1-3, and then flow through the guide holes 1-4 at the top and bottom of the guide edges 1-3. Figure 3-5 As shown, mounting hole groups 1-2 are provided on both sides of the exhaust port outlet of the cylinder head 1. The mounting hole groups 1-2 are located above the guide hole 1-4 at the top of the guide edge 1-3 and below the guide hole 1-4 at the bottom of the guide edge 1-3. The exhaust pipe 3 is fixed to the front end of the exhaust port outlet of the cylinder head 1 through the mounting holes. The top of the exhaust pipe 3 is connected to the turbocharger assembly 2. The exhaust pipe 3 has a segmented structure, and a sealing structure is provided at the connection of the segmented structure. The sealing structure is a sealing rope 7, which consists of an outer high-temperature resistant braided rope protective layer and an inner core expansion layer. The high-temperature resistant braided rope protective layer consists of 54-58% Si + 2-6% C, and the inner core expansion layer consists of 40% Al + O. The heat-resistant braided protective layer can also be 50% (44-48% Si + 2-6% C), 55% (50-53% Si + 2-5% C), or 65% (60-63% Si + 2-5% C). The inner core expansion layer can also be 50%, 45%, or 35%. Specific parameters can be selected according to different engine performance requirements. The sealing structure, through the aforementioned composition, forms a 10-30mm long fiber structure, woven to the required length. Even if the outer protective layer is damaged, the inner core expansion layer can maintain its shape, ensuring continuous high temperature resistance ≥850°C, instantaneous high temperature resistance ≥1000°C, and longitudinal tensile strength ≥250N, thus guaranteeing high-temperature sealing performance.

[0038] Of course, the sealing rope can also be composed of a composite of aluminum silicate, calcium silicate, aluminum silicate carbonate and modified silica gel, and its components can be referred to the above.

[0039] The high-temperature braided rope protective layer is wrapped around the outer part of the inner core expansion layer by braiding. The inner core expansion layer is made by extrusion molding. The sealing rope is assembled in the sealing ring groove of the exhaust pipe connection. After the engine is running, the exhaust temperature heats the sealing rope, which expands and fills the sealing ring groove to make up the gap and achieve the sealing effect.

[0040] Mounting hole group 1-2 consists of bolt holes, distributed at four corners on the front end face of cylinder head 1. An exhaust outlet 1-5 is provided in the middle of the mounting hole group 1-2 distributed at four corners. The air inlet of exhaust pipe 3 is connected to the exhaust outlet 1-5 of cylinder head 1. The number of mounting hole groups 1-2 matches the number of exhaust outlets 1-5. Each mounting hole group 1-2 is designed with four flange bolt holes to ensure that there is no dead zone for water flow at the top water cavity of the exhaust passage on cylinder head 1, i.e., at the top of the guide hole 1-4 of the guide edge 1-3, due to the bolts of the exhaust pipe.

[0041] An exhaust pipe for a six-cylinder four-valve engine exhaust system has an external heat insulation layer consisting of a metal wrapping and a soft wrapping. In order to meet the regeneration temperature requirements of the DPF aftertreatment for off-road T4 exhaust, as well as the requirements of heat insulation, anti-scalding and fire prevention, the exhaust pipe 3 is wrapped with a heat-insulating metal wrapping and soft wrapping with a total thickness of 10mm, so that the temperature of the outermost surface of the exhaust pipe is below 150°.

[0042] The exhaust pipe 3 includes a central pipe 3-1 and an exhaust branch pipe 3-2. An exhaust branch pipe 3-2 is connected to each side of the central pipe 3-1. A sealing structure is installed at the connection between the central pipe 3-1 and the exhaust branch pipe 3-2. The rear end of the central pipe 3-1 has a left intake port and a right intake port that communicate with the exhaust outlet 1-5 of the cylinder head 1. The central pipe 3-1 has several mounting holes distributed at four corners, namely hole A 3-1-2, hole B 3-1-3, and hole C 3-1-1. Holes A 3-1-2 and B 3-1-3 are respectively located on the flange end faces of the left and right intake ports. Hole A... Hole 3-1-2 is located at the upper right corner of the flange end face of the left intake port. Hole B 3-1-3 is located at the upper right corner of the flange end face of the right intake port. The rest are C holes 3-1-1. Holes A 3-1-2 and B 3-1-3 are located on the same transverse plane. The positioning error of holes A 3-1-2 and B 3-1-3 in the transverse and longitudinal directions is less than 0.5mm. The fitting clearance between C holes is 1mm to ensure that the clearance between the long bolt 6 and the mounting hole group is greater than 0 when the exhaust pipe 3 expands at high temperature. This ensures that the long bolt and the holes in the mounting hole group will not interfere, so as to avoid stress caused by interference, which could cause the exhaust pipe 3 to break at high temperature. The exhaust branch pipes 3-2 at both ends adopt a similar structure. The long bolt 6 that fixes the exhaust pipe 3 to the cylinder head 1 is fitted with a heat insulation sleeve 5. The heat insulation sleeve 5 can increase heat dissipation and compensate for the loosening of the long bolt 6 caused by thermal expansion. The exhaust branch pipes 3-2 on the left and right sides of the middle pipe 3-1 also adopt the same installation and fitting method as the middle pipe 3-1.

[0043] The outer surface of the intermediate pipe 3-1 is provided with several reinforcing ribs. In the non-road T4 emission stage, in order to control the regeneration temperature of the DPF aftertreatment, the turbine exhaust connection pipe between the turbocharger exhaust outlet and the aftertreatment inlet on the exhaust pipe needs to be covered with a soft package and metal wrapping. Considering the investment cost of stamping molds and the limited space of the tractor's overall hood, a larger arrangement space needs to be reserved between the turbocharger exhaust outlet and the hood. The connection surface of the turbocharger assembly 2 on the exhaust pipe 3 needs to be designed close to the side of the exhaust pipe 3 of the cylinder head 1, based on the characteristics of the tractor's slender and tall hood. At the same time, in order to avoid the cylinder head cover, space is reserved for the turbine exhaust connection pipe with increased wrapping thickness, and the turbocharger connection port is designed to be heightened. By arranging reasonable reinforcing ribs, the fatigue strength safety factor of the exhaust pipe 3 is ensured to be greater than 1.5.

[0044] An exhaust pipe gasket 4 is provided between the exhaust outlet 1-5 of the cylinder head 1 and the intake port of the exhaust pipe 3. The exhaust pipe gasket 4 is a double-layer full-wave 1Cr17Ni7 stainless steel exhaust pipe gasket with a working linear voltage greater than 10N / mm to ensure the sealing of exhaust gas during operation and avoid performance degradation and oil leakage caused by high-temperature exhaust gas leakage and cylinder head cover gasket burnout.

[0045] The exhaust pipe 3 is made of the following material: C: 2.8-3.6%, Si: 4.3-4.7%, Mn: ≤0.3%, P: ≤0.05%, S: ≤0.02%, Mo: 0.5-0.7%, Cr: ≤0.5%, Ni: ≤0.6%, Cu: ≤0.5%, Ti: ≤0.2%, with the balance being molten iron.

[0046] Using the above-mentioned raw materials, the process involves sand mixing, shaping, core setting, mold assembly, melting, and finally casting, followed by static cooling to solidify.

[0047] Exhaust pipes manufactured using the above-mentioned components have ferrite F≥90%, P+Mo special carbides ≤8%, and graphite vermicularization rate ≥50%. This exhaust pipe exhibits enhanced high-temperature resistance through high Cr, high Ni, and Ti content, achieving sustained high-temperature resistance up to 680°C and instantaneous high-temperature resistance up to 720°C. Figure 9 As shown, the tensile strength of silicon molybdenum vermicular iron material at different temperatures is represented by the horizontal axis as temperature and the vertical axis as tensile strength. The tensile strength is 55 MPa at 720°C, 41.5 MPa at 750°C, and 400 MPa at room temperature. The tensile strength decreases by 86.3% at 720°C.

[0048] like Figure 10 As shown, the maximum temperature is 670°C, the maximum allowable exhaust temperature at the exhaust pipe outlet is 700°C, and the recommended maximum operating temperature of this exhaust pipe material is 730°C, which meets the requirements.

[0049] like Figure 11 As shown, this is the temperature time history of the node with the highest temperature. The horizontal axis represents time in seconds (S), and the vertical axis represents the node temperature. In other words, it shows the temperature rise of the node with the highest temperature over time.

[0050] By optimizing the structure of the exhaust pipe, the exhaust pipe meets the requirements under high-temperature exhaust at 670°C and vibration loading conditions, avoiding problems such as interference caused by gap changes after thermal expansion, vibration fracture under thermal stress, axial force attenuation of the long bolt 6, loosening of the bolt, and sealing failure of the exhaust pipe gasket 4.

[0051] After simulation analysis and calculation, simulation results and data were obtained, and the following conclusions were drawn from the simulation results and data: (1) The highest temperature field of the exhaust pipe when the engine is working is 670°. The exhaust pipe material used can withstand high temperatures up to 680° and instantaneous high temperatures up to 720°, and can work reliably; (2) The minimum safety factor of the high cycle fatigue strength of the exhaust pipe is 1.52, which is greater than the standard requirement of 1.2; (3) The sealing performance of the exhaust pipe (the linear pressure distribution of the gasket sealing area of ​​the exhaust pipe) is calculated to be 13.86 N / mm, which meets the requirement of ≥10 N / mm.

Claims

1. An exhaust system for a six-cylinder, four-valve engine, comprising a cylinder head containing coolant and having a plurality of cooling water passages within the cylinder head, characterized in that: The cylinder head has several vertically spaced guide edges arranged horizontally inside. Guide holes are formed between the guide edges and the top and bottom surfaces of the cylinder head. The front end face of the cylinder head has a set of mounting holes, which are located above the guide holes at the top of the guide edges and below the guide holes at the bottom of the guide edges. It also includes an exhaust pipe, which is fixed to the front end of the cylinder head through mounting holes. The exhaust pipe has a segmented structure, and a sealing structure is provided at the joints of the segmented structure.

2. The exhaust system for a six-cylinder, four-valve engine according to claim 1, characterized in that: The mounting hole group consists of bolt holes, which are distributed at four corners on the front end face of the cylinder head. An exhaust hole is provided in the middle of the mounting hole group distributed at four corners. The air inlet of the exhaust pipe is connected to the exhaust outlet of the cylinder head.

3. The exhaust system for a six-cylinder, four-valve engine according to claim 1, characterized in that: The number of mounting hole groups matches the number of exhaust outlets.

4. The exhaust system for a six-cylinder, four-valve engine according to claim 1, characterized in that: The exhaust pipe includes a central pipe and an exhaust branch pipe. The central pipe has a left air intake port and a right air intake port. The central pipe has several mounting holes, which are divided into holes A, B and C. Holes A and B are respectively located on the flange surfaces of the left air intake port and the right air intake port, and the rest are holes C. Holes A and B are located on the same transverse plane, and the positioning error of holes A and B in the transverse and longitudinal directions is less than 0.5 mm.

5. The exhaust system for a six-cylinder, four-valve engine according to claim 4, characterized in that: The fit clearance between the C holes is 1 mm.

6. The exhaust system for a six-cylinder, four-valve engine according to claim 4, characterized in that: The outer surface of the intermediate tube is provided with several reinforcing ribs.

7. The exhaust system for a six-cylinder, four-valve engine according to claim 1, characterized in that: An exhaust pipe gasket is provided between the exhaust port of the cylinder head and the intake port of the exhaust pipe.

8. The exhaust system for a six-cylinder, four-valve engine according to claim 1, characterized in that: The sealing structure is a sealing rope, which consists of an outer high-temperature resistant braided rope protective layer and an inner core expansion layer. The high-temperature resistant braided rope protective layer is composed of Si+C, and the inner core expansion layer is composed of Al+O.

9. A six-cylinder four-valve engine exhaust system according to any one of claims 1-8, characterized in that: The exhaust pipe is made of the following material: C: 2.5-3.8%, Si: 3.5-4.9%, Mn: ≤0.4%, P: ≤0.07%, S: ≤0.06%, Mo: 0.4-0.9%, Cr: ≤0.5%, Ni: ≤0.6%, Cu: ≤0.7%, Ti: ≤0.4%, with the balance being molten iron.

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