Pistons and their design methods

Abstract

This invention discloses a piston and its design method, relating to the field of piston technology. The piston includes a skirt and a head connected to the top of the skirt. The skirt has a pin hole extending transversely through the skirt. Two hole sides are located on either side of the skirt along the transverse direction. A main thrust side and a secondary thrust side are formed on either side of the skirt along the longitudinal direction. The main thrust side has two first grooves recessed towards the secondary thrust side, both located near the bottom of the skirt and spaced apart transversely. The secondary thrust side has a second groove recessed towards the main thrust side, located near the top of the skirt. The piston provided by this invention can effectively avoid stress concentration, reduce abnormal wear, has a long service life, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of piston technology, and in particular to a piston and its design method. Background Technology

[0002] During piston operation, especially when the piston reverses direction at top and bottom dead centers, local stress concentration is prone to occur on the main thrust side and the secondary thrust side of the piston skirt. This is especially true in engine operating conditions with long strokes and low viscosity oil, where local stress concentration on the main thrust side and the secondary thrust side is more likely to cause abnormal wear on the piston skirt, resulting in a shorter piston life and poor reliability. Summary of the Invention

[0003] The main objective of this invention is to propose a piston and its design method, aiming to solve the technical problems of short piston service life and poor reliability.

[0004] To achieve the above objectives, the piston proposed in this invention includes a skirt and a head connected to the top of the skirt. The skirt has a pin hole that extends laterally through the skirt. The skirt has two hole sides on its two sides along the lateral direction. The skirt has a main thrust side and a secondary thrust side on its two sides along the longitudinal direction. The main thrust side has two first grooves that are recessed toward the secondary thrust side. The two first grooves are both located near the bottom of the skirt and are spaced apart laterally. The secondary thrust side has a second groove that is recessed toward the main thrust side and is located near the top of the skirt.

[0005] In one embodiment, the main thrust side is an axisymmetric structure extending longitudinally from the head in a direction away from the head, and the two first grooves are symmetrically arranged with respect to the axisymmetric line of the main thrust side.

[0006] In one embodiment, both first grooves are circular grooves, and the radius of the groove opening of both first grooves is R, wherein 2mm≤R≤4mm.

[0007] In one embodiment, the bottom end face of the main thrust side is a horizontal end face, and the vertical distance between the top edge of each of the first grooves and the bottom end face of the main thrust side is h1, wherein 8mm≤h1≤12mm.

[0008] In one embodiment, the two first grooves are respectively disposed near the two orifice sides, and the lateral distance between the side edge of each first groove and the orifice side it is adjacent to is L1, wherein 1mm≤L1≤2mm.

[0009] In one embodiment, the secondary thrust side is an axisymmetric structure extending longitudinally from the head in a direction away from the head, and the first groove is symmetrically arranged with respect to the axisymmetric line of the secondary thrust side.

[0010] In one embodiment, the second groove is an elliptical groove, the major axis of the second groove is arranged laterally, the radius of the major axis at the opening of the second groove is a, and the lateral dimension of the main thrust side is Watts; wherein, 0.5≤a / Wats≤0.8.

[0011] In one embodiment, the top surface of the secondary thrust side is a horizontal end face, and the distance between the top edge of the second groove and the top surface of the skirt is h2, wherein 2mm≤h2≤3mm.

[0012] In one embodiment, the groove depth of the first groove is ΔA, and the groove depth of the second groove is ΔB, wherein 10μm≤ΔA≤15μm, and 5μm≤ΔB≤10μm.

[0013] The present invention also proposes a piston design method, which is used to design the aforementioned piston, and the design method includes the following steps: Obtain the thermal and mechanical loads of the piston under normal operating conditions; Based on the thermal load and the mechanical load, and according to Hertzian contact theory, the set of contact pressure values ​​between the piston skirt and the cylinder liner is calculated. A contact pressure cloud diagram between the piston skirt and the cylinder liner is drawn based on the set of contact pressure values. Obtain the location of the maximum contact pressure on the piston as shown in the contact pressure cloud map, and determine the location of the maximum contact pressure and its surrounding area as the control area; The positions of the two first grooves on the main thrust side and the second groove on the auxiliary thrust side are determined according to the control area, and the shapes of the two first grooves and the second groove are determined according to the set of contact pressure values.

[0014] The technical solution of this invention utilizes two laterally spaced first grooves near the bottom of the piston skirt on the main thrust side. During piston reversal, these two first grooves undergo controllable micro-deformation, absorbing lateral impact and weakening the stress peak at that point. On the secondary thrust side, a second groove near the top of the piston skirt provides buffering during piston reversal, reducing stress concentration and lowering the overall maximum stress value of the skirt. Even under engine operating conditions involving long strokes and low-viscosity oil, the two first and second grooves on the skirt reduce localized stress concentration on both the main and secondary thrust sides of the piston skirt, effectively reducing the possibility of frictional damage to the piston, lowering the risk of abnormal wear, extending service life, and increasing reliability. Furthermore, the reduction of piston stress concentration is achieved solely through the first and second grooves designed on the skirt. The structure is simple, can be directly formed in the casting blank without additional machining, is easy to manufacture, and has minimal impact on piston weight and cost. Attached Figure Description

[0015] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the piston embodiment provided by the present invention from a certain perspective. Figure 2 A schematic diagram of the piston embodiment provided by the present invention from another perspective; Figure 3 A schematic diagram of the structure of a piston provided by the present invention, showing the skirt located on the main thrust side; Figure 4 A schematic diagram of the structure of a piston provided by the present invention, showing the skirt located on the secondary thrust side; Figure 5 This is a flowchart illustrating an embodiment of the piston design method provided by the present invention.

[0017] Explanation of icon numbers: 100. Piston; 10. Skirt; 11. Orifice side; 12. Main thrust side; 121. First groove; 13. Secondary thrust side; 131. Second groove; 20. Head.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0022] This invention proposes a piston 100.

[0023] Please see Figures 1 to 4 In one embodiment of the present invention, the piston 100 includes a skirt 10 and a head 20 connected to the top of the skirt 10. The skirt 10 has a pin hole that extends laterally through the skirt 10. The two sides of the skirt 10 along the lateral direction are two hole sides 11. The two sides of the skirt 10 along the longitudinal direction are formed with a main thrust side 12 and a secondary thrust side 13. The main thrust side 12 has two first grooves 121 that are recessed toward the secondary thrust side 13. The two first grooves 121 are both located near the bottom of the skirt 10 and are spaced apart laterally. The secondary thrust side 13 has a second groove 131 that is recessed toward the main thrust side 12. The second groove 131 is located near the top of the skirt 10.

[0024] In the technical solution of this invention, the piston 100 includes a skirt 10 and a head 20 connected to the top of the skirt 10. The skirt 10 has a pin hole that extends laterally through the skirt 10. The skirt 10 has two orifice sides 11 along its lateral sides, with the two orifices of the pin hole located on the two orifice sides 11 respectively. A main thrust side 12 and a secondary thrust side 13 are formed along its longitudinal sides. The main thrust side 12 has two first grooves 121 recessed towards the secondary thrust side 13. Both first grooves 121 are located near the bottom of the skirt 10 and are distributed laterally at intervals on the main thrust side 12. The secondary thrust side 13 has a second groove 131 recessed towards the main thrust side 12, located near the top of the skirt 10. Both the first grooves 121 and the second groove 131 are recessed only from the outer surface of the skirt 10 and do not penetrate the outer surface, thus maintaining the integrity of the outer contour of the skirt 10. This invention utilizes two laterally spaced first grooves 121 on the main thrust side 12 near the bottom of the skirt 10. When the piston 100 reverses direction downwards, the two first grooves 121 undergo controllable micro-deformation to absorb lateral impact and weaken the stress peak at that point. On the secondary thrust side 13, a second groove 131 near the top of the skirt 10 provides buffering when the piston 100 reverses direction upwards, reducing stress concentration and lowering the overall maximum stress value of the skirt 10. Even under engine operating conditions with long strokes and low-viscosity engine oil, the arrangement of the two first grooves 121 and the second groove 131 on the skirt 10 reduces local stress concentration on the main thrust side 12 and secondary thrust side 13 of the piston 100 skirt 10, effectively reducing the possibility of frictional damage to the piston 100, lowering the risk of abnormal wear, extending service life, and increasing reliability. Furthermore, the stress concentration of the piston 100 can be reduced by the first groove 121 and the second groove 131 designed in the skirt 10. The structure is simple, can be directly formed in the casting blank, does not require additional machining, is easy to manufacture, and has minimal impact on the weight and cost of the piston 100.

[0025] In one embodiment of the present invention, the main thrust side 12 is an axisymmetric structure extending longitudinally from the head 20 to a direction away from the head 20, and the two first grooves 121 are symmetrically arranged with respect to the axisymmetric line of the main thrust side 12.

[0026] Specifically, the main thrust side 12 extends longitudinally from the head 20 in a direction away from the head 20 and is axially symmetrical, with its line of symmetry coplanar with the central axis of the piston 100 and perpendicular to the pin hole axis. Two first grooves 121 are located on both sides of the line of symmetry of the main thrust side 12 and are arranged in a mirror image symmetrical arrangement relative to this line of symmetry. This ensures that the lateral distance from the groove to the edge of the pin hole, the longitudinal distance to the bottom of the skirt 10, and the length, width, and depth of the groove itself are all mirror images of each other, thereby guaranteeing a symmetrical stiffness distribution and deformation pattern of the main thrust side 12 when subjected to lateral forces. The symmetrical arrangement of the two first grooves 121 ensures that the micro-deformation of the main thrust side 12 during piston 100 reversal is uniform and consistent, avoiding local stress shifts and further reducing stress concentration; simultaneously, it ensures a symmetrical distribution of contact pressure between the skirt 10 and the cylinder wall, preventing eccentric friction, improving wear uniformity, extending service life, and enhancing operational reliability.

[0027] In one embodiment of the present invention, both first grooves 121 are circular grooves, and the radius of the groove opening of both first grooves 121 is R, wherein 2mm≤R≤4mm.

[0028] Furthermore, designing the first groove 121 as a circular recess allows for a larger opening area at the same depth, resulting in a smoother stress release. The rounded edge eliminates sharp corners, minimizing stress concentration and preventing the formation of new microcrack sources. This radius range of 2mm to 4mm ensures that the first groove 121 has sufficient deformation capacity without excessively weakening the rigidity of the skirt 10, ensuring that the piston 100 maintains high reliability under long-stroke, low-viscosity oil conditions, thus further extending the lifespan of the piston 100.

[0029] In one embodiment of the present invention, the bottom end face of the main thrust side 12 is a horizontal end face, and the vertical distance between the top edge of each first groove 121 and the bottom end face of the main thrust side 12 is h1, wherein 8mm≤h1≤12mm.

[0030] Furthermore, the bottom surface of the main thrust side 12 is a horizontal end face. The vertical distance between the top edge of the two circular first grooves 121 and the horizontal end face is h1. The distance h1 is controlled within the range of 8mm to 12mm, so that the first groove 121 is exactly in the area of ​​maximum tensile stress concentration when the piston 100 moves downward and reverses direction, thereby generating micro-deformation to absorb the impact in the first time. This avoids the weakening effect being insufficient if the distance is too large, and avoids the rigidity of the bottom end face being easily affected if the distance is too small. The distance h1 is within this range, which can take into account both stress release and structural strength, and can also ensure or have good structural strength, effectively extending the life of the piston 100 and improving the reliability of the piston 100.

[0031] In one embodiment of the present invention, two first grooves 121 are respectively disposed close to two orifice sides 11, and the lateral distance between the side edge of each first groove 121 and the orifice side 11 it is close to is L1, wherein 1mm≤L1≤2mm.

[0032] Furthermore, the two first grooves 121 are respectively arranged close to the two orifice sides 11, and the lateral distance L1 between the outermost edge of each first groove 121 and the inner wall of the adjacent orifice side 11 is controlled within 1mm~2mm. When L1 is in the range of 1mm~2mm, the first groove 121 is close to the high stress area of ​​the pin hole, which can release the tensile stress transmitted from the edge of the pin hole to the main thrust side 12 in an instant; it avoids the fact that the distance is too small, which will weaken the rigidity of the orifice, and avoids the fact that the distance is too large, which will reduce the buffering effect. This range achieves a balance between releasing stress and maintaining the strength of the pin hole, further suppressing the initiation of microcracks, extending the service life of the piston 100 and improving reliability.

[0033] In one embodiment of the present invention, the secondary thrust side 13 is an axisymmetric structure extending longitudinally from the head 20 in a direction away from the head 20, and the first groove 121 is symmetrically arranged with respect to the axisymmetric line of the secondary thrust side 13.

[0034] Specifically, the secondary thrust side 13 extends longitudinally from the head 20 in a direction away from the head 20 and is itself an axisymmetric structure. Its line of symmetry is coplanar with the central axis of the piston 100 and perpendicular to the pin hole axis. The second groove 131 is formed on this line of symmetry. The second groove 131 is also an axisymmetric structure, and its axis of symmetry coincides with the line of symmetry of the secondary thrust side 13, making the curvature of the left and right sides of the groove and the distance to the pin hole completely symmetrical. The second groove 131 is an axisymmetric structure with the line of symmetry of the secondary thrust side 13 as its axis of symmetry. This ensures that the lateral force is evenly applied to both sides of the groove when the piston 100 moves upward and reverses direction, avoiding stress skew. It also ensures a balanced pressure distribution between the skirt 10 and the cylinder wall, preventing localized eccentric wear, further reducing the risk of abnormal wear, extending service life, and improving operational reliability.

[0035] In one embodiment of the present invention, the second groove 131 is an elliptical groove, the major axis of the second groove 131 is arranged in the transverse direction, the radius of the major axis at the groove opening of the second groove 131 is a, and the transverse dimension of the main thrust side 12 is Watt; wherein, 0.5≤a / Wats≤0.8.

[0036] Furthermore, the second groove 131 is an elliptical groove, with its major axis arranged laterally and its minor axis arranged longitudinally. The ratio of the major axis radius a of the second groove 131 to the lateral width Wats of the main thrust side 12 is controlled between 0.5 and 0.8. This ratio ensures that the second groove 131 occupies a sufficient width laterally along the secondary thrust side 13, simultaneously covering the area of ​​maximum compressive stress on the secondary thrust side 13, thus releasing stress more effectively. This avoids insufficient buffer area due to an excessively small ratio, and also avoids weakening the overall rigidity of the skirt 10 due to an excessively large ratio. The 0.5–0.8 range balances stress release and structural strength, effectively reducing stress concentration, extending the life of the piston 100, and improving reliability.

[0037] In one embodiment of the present invention, the top surface of the secondary thrust side 13 is a horizontal end face, and the distance between the top edge of the second groove 131 and the top surface of the skirt 10 is h2, wherein 2mm≤h2≤3mm.

[0038] Furthermore, the top surface of the secondary thrust side 13 is a horizontal end face, and the longitudinal distance h2 between the top edge of the elliptical second groove 131 and this horizontal end face is controlled within 2mm~3mm. The 2mm~3mm range of h2 ensures that the second groove 131 is precisely located in the top region where the compressive stress is most concentrated during the upward reversal of the piston 100, allowing for immediate micro-deformation to absorb impact. This also avoids the buffering effect being weakened if the distance to the top surface of the secondary thrust side 13 is too large, and the top surface rigidity being easily affected if the distance is too small, effectively extending the service life of the piston 100 and improving its reliability.

[0039] In one embodiment of the present invention, the groove depth of the first groove 121 is ΔA, and the groove depth of the second groove 131 is ΔB, wherein 10μm≤ΔA≤15μm, and 5μm≤ΔB≤10μm.

[0040] Specifically, the groove depth ΔA of the first groove 121 is the depth of the first groove 121 recessed toward the secondary thrust side 13, and the groove depth ΔB of the second groove 131 is the depth of the second groove 131 recessed toward the main thrust side 12. ΔA is in the range of 10μm to 15μm and ΔB is in the range of 5μm to 10μm. This has little impact on the overall rigidity of the skirt 10, and can also prevent oil accumulation and foreign matter embedding. Furthermore, it can effectively reduce stress concentration in the piston 100, extend the life of the piston 100, and improve operational reliability.

[0041] The present invention also proposes a design method for a piston 100, which is used to design a piston 100 and includes the following steps: S100, obtain the thermal load and mechanical load of the piston under normal operating conditions; S200, based on the thermal load and the mechanical load, and according to Hertzian contact theory, calculates a set of contact pressure values ​​between the piston skirt and the cylinder liner; S300, draw a contact pressure cloud map between the piston skirt and the cylinder liner based on the set of contact pressure values; S400, obtain the position of the maximum contact pressure on the piston shown in the contact pressure cloud map, and determine the position of the maximum contact pressure and its surrounding area as the control area; S500, determine the positions of the two first grooves on the main thrust side and the second groove on the auxiliary thrust side according to the control area, and determine the shapes of the two first grooves and the second groove according to the set of contact pressure values.

[0042] The specific structure of the piston 100 is as described in the above embodiments. Since the design method of the piston 100 adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0043] Specifically, the design method for piston 100 first obtains the thermal and mechanical loads of piston 100 during normal operation through engine hot testing and simulation coupling. After superimposing the thermal and mechanical loads, the contact pressure between skirt 10 and piston 100 cylinder is calculated point by point according to Hertzian contact theory, resulting in a pressure value set. This set is mapped onto a mesh model to generate a contact pressure cloud map. The maximum contact pressure in the contact pressure cloud map is extracted, and the surrounding area is delineated as the control area centered on it. Based on the control area, two first grooves 121 are arranged at positions near the bottom of skirt 10 on the main thrust side 12, and a second groove 131 is arranged at a position near the top of skirt 10 on the secondary thrust side 13. By quantitatively positioning the piston 100 during normal operation using thermal and mechanical loads and Hertzian contact theory, it is ensured that the first groove 121 and the second groove 131 fall precisely in the region of maximum contact pressure and its highest gradient, resulting in precise stress release and avoiding blindly slotting to weaken irrelevant parts. This significantly reduces the peak contact pressure and weakens stress concentration. Furthermore, the entire process is based on a conventional simulation platform, requiring no additional experiments, resulting in a short design cycle and low cost.

[0044] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the protection scope of the present invention.

Claims

1. A piston, characterized in that, The piston includes a skirt and a head connected to the top of the skirt. The skirt has a pin hole that extends laterally through the skirt. The skirt has two hole sides on its two sides along the lateral direction. The skirt has a main thrust side and a secondary thrust side on its two sides along the longitudinal direction. The main thrust side has two first grooves that are recessed toward the secondary thrust side. The two first grooves are both located near the bottom of the skirt and are spaced apart laterally. The secondary thrust side has a second groove that is recessed toward the main thrust side. The second groove is located near the top of the skirt.

2. The piston as claimed in claim 1, characterized in that, The main thrust side is an axisymmetric structure extending longitudinally from the head in a direction away from the head, and the two first grooves are symmetrically arranged with respect to the axisymmetric line of the main thrust side.

3. The piston as described in claim 2, characterized in that, Both of the first grooves are circular grooves, and the radius of the groove opening of both of the first grooves is R, where 2mm≤R≤4mm.

4. The piston as claimed in claim 3, characterized in that, The bottom surface of the main thrust side is a horizontal end face, and the vertical distance between the top edge of each of the first grooves and the bottom surface of the main thrust side is h1, where 8mm≤h1≤12mm.

5. The piston as claimed in claim 4, characterized in that, The two first grooves are respectively disposed close to the two orifice sides, and the lateral distance between the side edge of each first groove and the orifice side it is close to is L1, wherein 1mm≤L1≤2mm.

6. The piston as claimed in any one of claims 1 to 5, characterized in that, The secondary thrust side is an axisymmetric structure extending longitudinally from the head in a direction away from the head, and the first groove is symmetrically arranged with respect to the axisymmetric line of the secondary thrust side.

7. The piston as claimed in claim 6, characterized in that, The second groove is an elliptical groove, the major axis of the second groove is set in the transverse direction, the radius of the major axis at the groove opening of the second groove is a, and the transverse dimension of the main thrust side is Watt; wherein, 0.5≤a / Wats≤0.

8.

8. The piston as claimed in claim 7, characterized in that, The top surface of the auxiliary thrust side is a horizontal end face, and the distance between the top edge of the second groove and the top surface of the skirt is h2, where 2mm≤h2≤3mm.

9. The piston as claimed in any one of claims 1 to 5, characterized in that, The depth of the first groove is ΔA, and the depth of the second groove is ΔB, wherein 10μm≤ΔA≤15μm and 5μm≤ΔB≤10μm.

10. A piston design method, characterized in that, The design method is used to design a piston as described in any one of claims 1 to 9, and the design method includes the following steps: Obtain the thermal and mechanical loads of the piston under normal operating conditions; Based on the thermal load and the mechanical load, and according to Hertzian contact theory, the set of contact pressure values ​​between the piston skirt and the cylinder liner is calculated. A contact pressure cloud diagram between the piston skirt and the cylinder liner is drawn based on the set of contact pressure values. Obtain the location of the maximum contact pressure on the piston as shown in the contact pressure cloud map, and determine the location of the maximum contact pressure and its surrounding area as the control area; The positions of the two first grooves on the main thrust side and the second groove on the auxiliary thrust side are determined according to the control area, and the shapes of the two first grooves and the second groove are determined according to the set of contact pressure values.

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