Background
The piston is the "heart" of the engine, is subject to alternating mechanical and thermal loads, and is one of the most severe critical components of the engine in terms of operating conditions. The piston has the function of bearing gas pressure and is transmitted to the connecting rod through the piston pin shaft to drive the crankshaft to rotate, and the failure of the piston can cause the engine to lose power and even cause the whole engine to be scrapped.
The existing large-cylinder-diameter piston (the piston with the cylinder diameter larger than 150 mm) is made of aluminum alloy, cast iron, a steel top aluminum skirt and a steel top iron skirt, the aluminum piston cannot meet the requirements along with the increase of the power of an engine, the cast iron piston has the defects of sand holes, air holes, slag inclusion and the like inevitably inside the cast iron piston due to the forming reason, the use risk is higher and higher along with the increase of the power, and the cost of the cast iron casting to the environment is further increased along with the increase of the environmental protection requirements. The steel top aluminum skirt and the steel top iron skirt are connected through the bolts, requirements on the size of a matching surface, the strength of the bolts, the pre-tightening force and the like are high, human factors have large influence, the assembling precision is difficult to achieve, and the problem is often caused by the combined piston. Along with the improvement of the rigidity of processing equipment and cutters, the integral forged steel piston is gradually added into the large-cylinder-diameter piston.
The large-bore integral forged steel piston replaces an aluminum alloy piston, a steel-top aluminum skirt piston, a steel-top iron skirt piston and an iron piston, the biggest problem is the weight problem, in order to reduce the weight of the steel piston, a blank surface is made in the direction of a piston pin hole, a weight reduction groove is additionally arranged between a piston oil ring groove and a skirt part, so that the weight of the piston can be reduced, but the guide of the skirt part of the piston is reduced, the lateral force borne by the skirt part is increased, and the eccentric wear phenomenon of the piston occurs.
The large-cylinder-diameter integral forged steel piston has a deep inner cavity, so that the tonnage of equipment required to be forged is large during forging, and the large-cylinder-diameter integral forged steel piston is difficult to be formed by one-step forging.
Therefore, the problem that needs to be solved by the technical personnel in the field is how to provide a large-cylinder-diameter integral forged steel piston which is reasonable in structure, safe, reliable and high in production efficiency.
Disclosure of Invention
Therefore, the invention aims to provide a large-cylinder-diameter integrally-forged steel piston, and solves the problems of low production efficiency and poor use safety of the conventional large-cylinder-diameter piston.
The invention provides a large-cylinder-diameter integrally forged steel piston, which comprises:
a piston head;
the piston skirt part, the piston skirt part and the piston head part are all forged parts, the top of the piston skirt part and the piston head part are fixedly formed into a piston body, a closed cooling oil cavity or two communicated double cooling oil cavities are formed inside the piston body, and a skirt part annular part is fixed at the lower end of the piston skirt part; the cross section of the corresponding oil ring groove lower ring land on the outer wall of the top of the piston skirt part is an ellipse with the major axis parallel to the direction of the piston pin hole, and the cross section and the skirt part annular part jointly participate in the guiding of the piston body.
According to the technical scheme, compared with the prior art, the invention discloses the large-cylinder-diameter integrally-forged steel piston, the piston head and the piston skirt blank are separately forged, the forging process is simplified, the requirement on the tonnage of equipment is reduced, and the equipment investment is reduced. The piston head and the piston skirt are machined, and the requirements on equipment and tools are reduced. The annular part of the piston skirt part is processed independently, the forging depth of the piston body skirt part can be reduced, and the forging and processing difficulty is reduced; the annular part of the piston skirt part and the annular land on the lower side surface of the oil ring groove jointly participate in piston guiding, so that the engine is favorable for stable operation, the eccentric wear phenomenon of the piston is reduced, and the use safety and reliability of the piston are improved.
Furthermore, the major axis of the ellipse of the lower ring land of the oil ring groove is 0.03-0.15mm smaller than the maximum dimension of the piston skirt. Under the working state, the maximum size of the piston skirt part is the same as the long axis size of the ring land at the lower part of the oil ring groove, and the guiding of the piston in the cylinder sleeve is ensured.
Further, the piston head and the piston skirt are made of modulation steel or non-modulation steel. The tempered steel can be 42CrMo, the non-tempered steel can be 38MnVS6, and the material of the skirt annular part is the same as or different from that of the skirt.
Further, the skirt annular portion height is greater than 5 mm; thereby securing a guide area of the participating guide portions.
Further, the skirt annular portion has an elliptical cross-section with a major axis perpendicular to the direction of the piston pin bore. Therefore, the lower side ring land of the oil ring groove is designed in a reverse ellipse mode (namely, the direction perpendicular to the piston pin hole is an ellipse short axis or the direction parallel to the piston pin hole is an ellipse long axis), the skirt part annular part is designed in a positive ellipse mode (namely, the direction perpendicular to the piston pin hole is an ellipse long axis), the guide of a piston body formed by the ring land and the skirt part annular part is guaranteed, the engine runs more stably, the eccentric wear phenomenon of the piston is reduced, and particularly, the large-cylinder-diameter medium-low-speed engine is provided.
Further, the skirt annular portion is forged or machined; piston skirt annular portion processes alone, and piston body skirt portion forges the degree of depth and can reduce, forges the degree of difficulty and reduces.
Further, the piston head and the piston skirt are fixed by one or a plurality of combinations of welding, threads or bolts.
Further, the piston head and the piston skirt are welded by electron beam or laser, and a vertical weld and a horizontal weld are formed at the joint of the piston head and the piston skirt.
Further, an annular weld is formed on the contact surface of the piston skirt and the skirt annular part. The annular part of the piston skirt part is less stressed, the requirement can be met by using a common welding mode, the welding efficiency is high, and the cost is low. Obviously, the skirt ring portion may also be integral with the piston body by means of threads, bolts, etc.
And further, the ring groove of the piston skirt part, the piston pin hole, the outer circle molded surface and the outer circle molded surface of the piston head part are manufactured by finish machining.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
Referring to the accompanying drawings 1-4, the embodiment of the invention discloses a large-bore integral forged steel piston, which comprises:
a piston head 1;
the piston skirt part 2, the piston skirt part 2 and the piston head part 1 are all forged parts, the top of the piston skirt part 2 and the piston head part 1 are fixed to form a piston body, an annular cooling oil cavity 21 and a basin-shaped cooling oil cavity 22 which are communicated with each other are formed in the piston body, and a skirt part annular part 3 is fixed to the lower end of the piston skirt part 2; the cross section of the corresponding oil ring groove lower ring land 4 on the outer wall of the top of the piston skirt 2 is an ellipse with the major axis parallel to the direction of the piston pin hole 5, and the cross section and the skirt annular part 3 jointly participate in the guiding of the piston body.
The invention discloses a large-cylinder-diameter integrally-forged steel piston, which is characterized in that a piston head and a piston skirt blank are separately forged, so that the forging process is simplified, the requirement on the tonnage of equipment is reduced, and the equipment investment is reduced. The piston head and the piston skirt are machined, and the requirements on equipment and tools are reduced. The annular part of the piston skirt part is processed independently, the forging depth of the piston body skirt part can be reduced, the production difficulty of the piston is reduced, and the production efficiency of the piston is improved; the annular part of the piston skirt part and the annular land on the lower side surface of the oil ring groove jointly participate in piston guiding, so that the engine is favorable for stable operation, the eccentric wear phenomenon of the piston is reduced, and the use safety and reliability of the piston are improved.
Wherein, the ellipse major axis size of the lower part of the oil ring groove is 0.03-0.15mm smaller than the maximum size of the piston skirt.
Advantageously, the piston head 1 and skirt 2 are made of tempered or non-tempered steel. The tempered steel can be 42CrMo, the non-tempered steel can be 38MnVS6, and the material of the skirt annular part is the same as or different from that of the skirt.
More advantageously, the skirt annular portion 3 is greater than 5mm high; thereby securing a guide area of the participating guide portions.
In the present embodiment, the skirt annular portion 3 has an elliptical cross-section with the major axis perpendicular to the direction of the piston pin bore 5. Therefore, the lower side ring land of the oil ring groove is designed in a reverse ellipse mode (namely, the direction perpendicular to the piston pin hole is an ellipse short axis or the direction parallel to the piston pin hole is an ellipse long axis), the skirt part annular part is designed in a positive ellipse mode (namely, the direction perpendicular to the piston pin hole is an ellipse long axis), the guide of a piston body formed by the ring land and the skirt part annular part is guaranteed, the engine runs more stably, the eccentric wear phenomenon of the piston is reduced, and particularly, the large-cylinder-diameter medium-low-speed engine is provided.
Wherein the skirt annular portion 3 is forged or machined. Piston skirt annular portion processes alone, and piston body skirt portion forges the degree of depth and can reduce, forges the degree of difficulty and reduces.
In the above embodiments, the piston head 1 and the piston skirt 2 are fixed by one or more combinations of welding, threads or bolts.
Preferably, the piston head 1 and the piston skirt 2 are welded by electron beam or laser, and a vertical weld 6 and a horizontal weld 7 are formed at the joint of the piston head 1 and the piston skirt 2. Thereby ensuring the cleanness inside the piston body and solving the problem that the welding slag is difficult to remove.
Wherein, an annular welding seam 8 is formed on the contact surface of the piston skirt 2 and the skirt annular part 3; the annular part of the piston skirt part is less stressed, the requirement can be met by using a common welding mode, the welding efficiency is high, and the cost is low. Obviously, the skirt ring portion may also be integral with the piston body by means of threads, bolts, etc.
In the above embodiment, the ring grooves of the skirt portion 2, the pin holes 5, the outer circumferential surface, and the outer circumferential surface of the head portion 1 are finished.
According to the invention, the piston head and the piston skirt are respectively subjected to rough machining, the piston head and the piston skirt are fixed to form a piston body, and a closed cooling oil cavity or two communicated double oil cavities is formed between the piston head and the piston skirt. The cooling oil cavity is communicated with the inner cavity of the piston or a pin hole through an oil inlet hole 11 and an oil outlet hole 12, the annular part of the skirt part of the piston is roughly turned and then integrated with the piston body in a welding, thread, bolt and other modes, and finally the finished product is obtained through heat treatment, finish machining and surface treatment, wherein the surface treatment has no special requirements and is the same as that of other types of pistons, so that the subsequent treatment process is not changed, and the subsequent process can be completed by adopting a previous production line.
The upper part of the piston skirt part is also provided with a weight reduction groove, so that the weight of the piston body is reduced.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.