Diesel engine valve

Abstract

The invention provides a diesel engine valve which comprises a valve head and a valve rod, one end of the valve rod is connected with the valve head, and a composite microstructure is arranged on the surface of the valve rod. The conical surface of the valve head is provided with a micro-pit texture. The composite microstructure comprises annular grooves and micro pits, the annular grooves are evenly distributed in the surface of the valve rod in the axial direction of the valve rod, and a plurality of first micro pits are evenly distributed in the positions, between the adjacent annular grooves, of the surface of the valve rod in the circumferential direction. The valve is an intake valve, the widths of the annular grooves are axially and progressively decreased from the center of the valve rod to the two sides, and the diameters and the depths of the first micro pits are axially and progressively increased from the center of the valve rod to the two sides. A stable lubricating oil film is formed between the valve rod and the valve guide pipe; the micro-pit texture arranged on the conical surface of the valve can generate an extrusion effect to form a hydrodynamic lubricating oil film, so that the frictional wear of the conical surface is reduced.

Description

Technical Field

[0001] The present invention relates to the field of diesel engine parts, in particular to a diesel engine valve. Background Art

[0002] Valves, including intake and exhaust valves, control the flow of gases into and out of the cylinder and seal the combustion chamber during engine operation. During engine operation, they are subjected to mechanical loads and thermal shock hundreds or even thousands of times per minute. When closed, the valves are subjected to a static pressure from the in-cylinder gas pressure, typically around 10 MPa. When seated, the valves are subject to an impact load of around 20 MPa. Intake valves operate at temperatures of approximately 200-450°C, while exhaust valves typically operate at temperatures of 600-800°C, with some exhaust valves reaching temperatures of 850-900°C. Valve materials are susceptible to creep deformation in high-temperature environments. Repeated impact can cause wear on the valve cone and guide rod, cracking and chipping of the head, and, in severe cases, ablation fracture. Valve wear can lead to poor combustion chamber sealing, directly impacting engine fuel economy and emissions. Valve wear or fracture can lead to minor valve and valvetrain replacement, or even complete engine replacement.

[0003] The existing friction reduction and wear resistance technologies for diesel engine valves mainly include the following:

[0004] 1. Surface coating technology: By coating the valve surface with hard materials (such as titanium nitride, tungsten carbide, etc.), its wear resistance and anti-friction performance are improved.

[0005] 2. Heat treatment technology: By subjecting the valve to heat treatment processes such as quenching, carburizing or nitriding, its surface hardness and wear resistance are improved.

[0006] 3. Material improvement: Use high-performance alloy materials to manufacture valves to improve their high temperature resistance, wear resistance and corrosion resistance.

[0007] 4. Lubrication technology: Reduce the friction between the valve and the seat by improving the lubricant or lubrication system.

[0008] The existing friction reduction and wear resistance technology for diesel engine valves has the following shortcomings: the coating may peel off and heat treatment may cause material embrittlement; high-performance materials and complex processes increase manufacturing costs; the exhaust valve has serious carbon deposits and poor heat dissipation performance. Summary of the Invention

[0009] In response to the shortcomings of the existing technology, the present invention provides a diesel engine valve, which is provided with a composite texture on the surface of the valve stem, and utilizes the coupling gain effect of annular grooves and micro-pits in fluid dynamic lubrication to form a stable lubricating oil film between the valve stem and the valve guide; the micro-pit texture is provided on the valve cone surface to produce an extrusion effect to form a fluid dynamic lubricating oil film, thereby reducing the friction and wear of the cone surface.

[0010] The present invention achieves the above technical objectives through the following technical means.

[0011] A diesel engine valve comprises a valve head and a valve stem, wherein one end of the valve stem is connected to the valve head, and the surface of the valve stem is provided with a composite micro-texture; the conical surface of the valve head is provided with a micro-pit texture for forming a friction-reducing zone to reduce the wear of the conical surface.

[0012] Furthermore, the composite micro-texture includes annular grooves and micro-pits, a plurality of the annular grooves are evenly distributed on the valve stem surface along the valve stem axis, and a plurality of first micro-pits are evenly distributed circumferentially on the valve stem surface between adjacent annular grooves.

[0013] Furthermore, the widths of the plurality of annular grooves increase along the axial direction of the valve stem and the diameters of the first micro-pits decrease along the axial direction of the valve stem.

[0014] Furthermore, the diameter of the first micro-pit is 60-100 μm, and the depth of the first micro-pit is 10-20 μm.

[0015] Furthermore, the valve is an intake valve, the widths of the plurality of annular grooves decrease axially from the center of the valve stem to both sides, and the diameter and depth of the first micro-pits increase axially from the center of the valve stem to both sides.

[0016] Furthermore, the valve is an outlet valve, the widths of the plurality of annular grooves increase axially from the center of the valve stem to both sides, and the diameter and depth of the first micro-pit decrease axially from the center of the valve stem to both sides.

[0017] Furthermore, the annular groove width l is 60-100 μm, and the annular groove depth h is 10-20 μm.

[0018] Furthermore, the conical surface of the valve head is provided with a plurality of second micro-pits, the diameters of the second micro-pits decrease gradually along the taper direction; the diameters of the second micro-pits are 50 to 80 μm, and the depths of the micro-pits are 10 to 20 μm.

[0019] The beneficial effects of the present invention are:

[0020] 1. The diesel engine valve described in the present invention has a composite texture provided on the valve stem surface, utilizing the coupling gain effect of annular grooves and micro-pits in fluid dynamic lubrication to form a stable lubricating oil film between the valve stem and the valve guide. The micro-pit texture provided on the valve cone surface can produce an extrusion effect to form a fluid dynamic lubricating oil film, thereby reducing friction and wear on the cone surface.

[0021] 2. The diesel engine valve described in the present invention is for the intake valve. Since the intake valve mainly allows air or mixed gas to enter the cylinder during the intake stroke, the operating temperature is relatively low (200-400°C). However, the particles carried by the air may cause wear, especially in the absence of turbocharging, there may be more impurities in the air. Therefore, the width of the annular groove decreases axially from the center of the valve stem to both sides, and the diameter and depth of the first micro-pit increase axially from the center of the valve stem to both sides. In this way, the intake valve has better wear resistance and self-cleaning ability. The widest annular groove in the central area can enhance the lubricating oil film retention ability, and the gradient-changing diameter of the first micro-pit forms a dynamic pressure field to promote the discharge of impurities.

[0022] 3. The diesel engine valve described in the present invention has a reverse gradient design for the intake valve (the width of the annular groove is the largest at the center), which utilizes the negative pressure effect when the piston moves downward. The wide annular groove in the center area forms a lubricating oil storage area, while the gradually shrinking groove width matches the valve movement acceleration to maintain a stable oil film.

[0023] 4. The diesel engine valve described herein, specifically the outlet valve, operates at extremely high temperatures due to the high exhaust temperature it emits during the exhaust stroke, making it susceptible to thermal corrosion and oxidation. Furthermore, the exhaust gas may contain combustion residues, which can easily lead to carbon deposits. By increasing the width of the annular groove axially from the center of the valve stem and decreasing the diameter and depth of the first micro-dimples axially from the center of the valve stem, the annular groove can disperse concentrated thermal stress, while the large-diameter micro-dimples in the central region enhance heat dissipation and forced convection cooling. Furthermore, carbon deposits in the central annular groove are prevented, and the decreasing micro-dimple size reduces the retention of high-temperature media. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a three-dimensional diagram of the diesel engine valve according to the present invention.

[0026] Figure 2 This is a cross-sectional view of the diesel engine valve according to the present invention.

[0027] Figure 3 Schematic diagram of the micro-pit texture of the valve head according to the present invention.

[0028] Figure 4 Schematic diagram of the valve stem composite texture according to the present invention.

[0029] Figure 5 This is a partial schematic diagram of the valve stem of the intake valve according to embodiment 1 of the present invention.

[0030] In the picture:

[0031] 1-valve head; 1-1-second micro-pit; 2-valve stem; 2-1-annular groove; 2-2-first micro-pit. DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0034] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] like Figure 1As shown, the diesel engine valve described in the present invention includes a valve head 1 and a valve stem 2, one end of the valve stem 2 is connected to the valve head 1, and the surface of the valve stem 2 is provided with a composite micro-texture; the conical surface of the valve head 1 is provided with a micro-pit texture, which is used to form a friction reduction zone to reduce the wear of the conical surface. By providing the composite micro-texture on the surface of the valve stem 2 and the micro-pit texture on the conical surface of the valve head 1, the friction characteristics and distribution of the valve surface can be optimized, the lubrication state can be improved, the mechanical properties such as the strength, hardness, and stress state of the valve surface material are improved, and the friction and wear energy and service life of the valve are improved. Under the same service conditions, the service life of the valve is increased by at least 15%; under the same service conditions, the thermal load of the valve is reduced by at least 30%.

[0036] like Figure 2 and Figure 4 As shown, the composite microtexture includes annular grooves 2-1 and first micro-dimples 2-2. Several annular grooves 2-1 are evenly distributed along the valve stem 2's surface axially. Several first micro-dimples 2-2 are evenly distributed circumferentially on the valve stem 2's surface between adjacent annular grooves 2-1. In this embodiment, the valve height H is 140 mm, the length L of the composite micro-texture region is approximately 44 mm, and the distance h1 from the bottom of the composite micro-texture region to the bottom of the valve head 1 is 55 mm. Therefore, the composite micro-texture region can be considered to be located essentially at the center of the valve stem 2. The number of annular grooves 2-1 is 10 to 15, the diameter of the first micro-dimples 2-2 is 60 to 100 μm, and the depth of the first micro-dimples 2-2 is 10 to 20 μm. The width l of the annular groove 2-1 is 60 to 100 μm, and the depth h of the annular groove 2-1 is 10 to 20 μm. In some embodiments, the widths of the annular grooves 2 - 1 gradually increase along the axial direction of the valve stem 2 , and the diameters of the first micro-pits 2 - 2 gradually decrease along the axial direction of the valve stem 2 .

[0037] Example 1

[0038] The valve is an intake valve, including a valve head 1 and a valve stem 2, one end of the valve stem 2 is connected to the valve head 1, and the surface of the valve stem 2 is provided with a composite micro-texture; the conical surface of the valve head 1 is provided with a micro-pit texture; the composite micro-texture includes an annular groove 2-1 and a first micro-pit 2-2, and several annular grooves 2-1 are evenly distributed on the surface of the valve stem 2 along the axial direction of the valve stem 2, and several first micro-pits 2-2 are evenly distributed circumferentially on the surface of the valve stem 2 between adjacent annular grooves 2-1; since the intake valve mainly allows air or mixed gas to enter the cylinder during the intake stroke, the operating temperature is relatively low (200-400°C), but the particles carried by the air may cause wear, especially in the absence of turbocharging, there may be more impurities in the air, so the width of several annular grooves 2-1 decreases axially from the center of the valve stem 2 to both sides, and the diameter and depth of the first micro-pit 2-2 increase axially from the center of the valve stem 2 to both sides. Specifically, Figure 5As shown: the width of the annular groove 2-1 is 80-100 μm in the central area (maximum in the axial direction), and the width of the annular groove 2-1 decreases to 60-80 μm towards both ends; the depth of the annular groove 2-1 is 15-20 μm; the diameter of the first micro-pit 2-2 is 60-80 μm in the central area (minimum in the axial direction), and the diameter of the first micro-pit 2-2 increases to 80-100 μm towards both ends; the depth of the first micro-pit 2-2 is 10-15 μm in the central area (minimum in the axial direction), and the depth of the first micro-pit 2-2 increases to 20-25 mm towards both ends; the intake valve has better wear resistance and self-cleaning ability, the widest annular groove 2-1 in the central area can enhance the lubricating oil film retention ability, and the gradient-changing diameter of the first micro-pit 2-2 forms a dynamic pressure field to promote the discharge of impurities. The intake valve's reverse gradient design (the annular groove width is largest at the center) utilizes the negative pressure effect when the piston moves downward. The wide annular groove in the center forms a lubricating oil storage area, while the gradually shrinking groove width matches the valve movement acceleration to maintain a stable oil film.

[0039] like Figure 3 As shown, the conical surface of the valve head 1 is provided with a plurality of second micro-dimples 1-1. The diameter of the second micro-dimples 1-1 decreases along the taper direction. The diameter of the second micro-dimples 1-1 is 80-100 μm, the depth is 15-20 μm, and the distribution density is 15-20 per square millimeter. The conical surface of the valve head 1 is provided with second micro-dimples 1-1. The larger second micro-dimples 1-1 effectively capture lubricant, and the high density distribution enhances the surface dynamic pressure effect. The larger size here refers to the second micro-dimples 1-1 relative to the intake valve.

[0040] Example 2

[0041] The valve is an outlet valve, comprising a valve head 1 and a valve stem 2, one end of which is connected to the valve head 1. The surface of the valve stem 2 is provided with a composite microtexture; the conical surface of the valve head 1 is provided with a micro-dimple texture; the composite microtexture includes annular grooves 2-1 and first micro-dimples 2-2, with a plurality of annular grooves 2-1 uniformly distributed along the axial direction of the valve stem 2, and a plurality of first micro-dimples 2-2 uniformly distributed circumferentially on the surface of the valve stem 2 between adjacent annular grooves 2-1. Because the outlet valve discharges high-temperature exhaust gas during the exhaust stroke, the operating temperature is extremely high, making it susceptible to thermal corrosion and oxidation. Furthermore, the exhaust gas may contain combustion residues that can easily lead to carbon deposits. Therefore, the widths of the annular grooves 2-1 increase axially from the center of the valve stem 2, while the diameters and depths of the first micro-dimples 2-2 decrease axially from the center of the valve stem 2. Specifically: the width of the annular groove 2-1 is 60-80μm in the central area (minimum in the axial direction), and the width of the annular groove 2-1 increases gradually to 80-100μm towards both ends; the depth of the annular groove 2-1 is 10-15μm; the diameter of the first micro-pit 2-2 is 80-100μm in the central area (maximum in the axial direction), and the diameter of the first micro-pit 2-2 decreases gradually to 60-80μm towards both ends; the depth of the first micro-pit 2-2 is 20-25μm in the central area (maximum in the axial direction), and the depth of the first micro-pit 2-2 decreases gradually to 10-15mm towards both ends; the annular groove can disperse the concentration of thermal stress, while the large-diameter micro-pits in the central area enhance the heat dissipation capacity and enhance forced convection heat dissipation; in addition, carbon deposition in the annular groove in the center can be avoided, and the decreasing micro-pit size reduces the retention of high-temperature media.

[0042] like Figure 3 As shown, the conical surface of the valve head 1 is provided with a plurality of second micro-pits 1-1, and the diameter of the second micro-pits 1-1 decreases along the taper direction; the diameter of the second micro-pits 1-1 is 60-80 μm, the depth of the micro-pits is 10-15 μm, and the distribution density is 20-25 per square millimeter; the conical surface of the valve head 1 is provided with second micro-pits 1-1, and the small-size and high-density micro-pits improve the sealing reliability, and the shallower depth prevents structural failure at high temperature. The small size and shallower depth here are relative to the second micro-pits 1-1 of the intake valve.

[0043] The diesel engine valve manufacturing method of the present invention comprises the following steps:

[0044] Step 1: The material is a diesel engine valve made of 282 nickel-based high-temperature alloy that has been machined and has the required dimensions, and the initial sample has been quenched and tempered.

[0045] Step 2, pre-treating the outer surface of the selected diesel engine valve, wherein the roughness parameter range of the surface after pre-treatment is: Ra≤0.8μm, Rz≤3.2μm, Rpk≤0.15μm, Rvk≤0.4μm, and roundness and cylindricity≤0.01mm;

[0046] In step 3, laser ablation microtexturing was performed using an MFPT-100H-YAGBA4.0 fiber nanosecond pulse laser marker. The laser had a pulse width of 170 ns, a wavelength of 1064 nm, a maximum power of 100 W, an adjustable average power between 0 and 100 W, and a repetition rate between 20 and 100 kHz. The processing method was a single pulse applied to the same point multiple times. In the experiment, the laser parameters were set to a scanning speed of 200 mm / s and a frequency of 20 kHz. The microtexturing parameters were varied by controlling the laser power and repetition rate.

[0047] Step 4, micro-texturing: After ultrasonic cleaning, fix the material on the workbench of the nanosecond pulse laser marking machine, and then focus to ensure that the defocus is 0. After setting the laser parameters such as average power and repetition number, micro-texturing is processed on the material surface using a single pulse repetitive processing method. The specific implementation process is as follows:

[0048] Using a diode-pumped YAG laser processing system, microtexturing was tested on valve material specimens. By adjusting the relationship between laser processing parameters and microtexture geometry, the optimal microtexture was achieved. Using a diode-pumped YAG laser and acousto-optic Q-switching technology, a laser micromachining control system was developed to meet specific process requirements, targeting valve guide surfaces and conical surfaces. Programming the MC8041A motion control card and a custom-built laser Q-switching control card enabled control of the mechanical motion system and the laser Q-switching signal output. The motion control card controlled the servo motors on each axis, while the laser Q-switching control card received feedback pulses from a high-precision incremental rotary encoder mounted on the rotating axis, counted and divided them, and output the required laser Q-switching signal. The laser Q-switching control card coordinated the rotational motion of the laser head and the output of individual laser pulses, meeting the micromachining requirements of "single pulse at the same point with multiple intervals," enabling efficient, flexible, and high-quality laser-based heterogeneous manufacturing of valve surfaces.

[0049] In step 5, the surface of the valve guide sample was treated with a composite texture using a laser microtexturing process. Tribological performance tests of the valve surface were conducted using an improved Rtec multifunctional friction and wear testing machine. The influence of the valve surface topographical parameters on the friction coefficient under different operating conditions was examined, and the corresponding Stribeck curves were plotted. The theoretical analysis focused on the influence of the composite texture geometric parameters on tribological performance. The experimental and theoretical results were then compared and analyzed, and the theoretical model was modified to further develop and improve the friction reduction mechanism of laser composite texturing on the valve guide surface.

[0050] Step 6, post-processing: After the micro-texture morphology and size detection is completed, the textured slag protrusions need to be polished, and ultrasonic cleaning is performed again for 15 minutes after polishing to remove impurities on the material surface.

[0051] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0052] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A diesel engine valve, comprising a valve head (1) and a valve stem (2), wherein one end of the valve stem (2) is connected to the valve head (1), characterized in that: The surface of the valve stem (2) is provided with a composite micro-texture; the conical surface of the valve head (1) is provided with a micro-pit texture, which is used to form a friction-reducing zone to reduce the wear of the conical surface.

2. The diesel engine valve according to claim 1, characterized in that: The composite micro-texture comprises annular grooves (2-1) and first micro-pits (2-2); a plurality of the annular grooves (2-1) are evenly distributed on the surface of the valve stem (2) along the axial direction of the valve stem (2); and a plurality of first micro-pits (2-2) evenly distributed in the circumferential direction are provided on the surface of the valve stem (2) between adjacent annular grooves (2-1).

3. The diesel engine valve according to claim 2, characterized in that: The widths of the plurality of annular grooves (2-1) increase axially along the valve stem (2), and the diameter of the first micro-pit (2-2) decreases axially along the valve stem (2).

4. The diesel engine valve according to claim 2, characterized in that: The diameter of the first micro-pit (2-2) is 60 to 100 μm, and the depth of the first micro-pit (2-2) is 10 to 20 μm; the width l of the annular groove (2-1) is 60 to 100 μm, and the depth h of the annular groove (2-1) is 10 to 20 μm.

5. The diesel engine valve according to claim 2, characterized in that: The valve is an intake valve, the widths of the plurality of annular grooves (2-1) decrease axially from the center of the valve stem (2) to both sides, and the diameter and depth of the first micro-pit (2-2) increase axially from the center of the valve stem (2) to both sides.

6. The diesel engine valve according to claim 2, characterized in that: The valve is an outlet valve, the widths of the plurality of annular grooves (2-1) increase axially from the center of the valve stem (2) to both sides, and the diameter and depth of the first micro-pit (2-2) decrease axially from the center of the valve stem (2) to both sides.

7. The diesel engine valve according to claim 1, characterized in that: The conical surface of the valve head (1) is provided with a plurality of second micro-pits (1-1), the diameter of the second micro-pits (1-1) decreases along the taper direction; the diameter of the second micro-pits (1-1) is 50 to 80 μm, and the depth of the micro-pits is 10 to 20 μm.

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