Steel piston and manufacturing process

Abstract

The application provides a steel piston and a manufacturing process, and relates to the technical field of internal combustion engine pistons.The application avoids the weld from the high-load area such as the top surface and the combustion chamber of the piston, reduces the influence of the welding defects in the weld on the piston, greatly prolongs the service life of the piston, and improves the reliability and safety of the piston operation;the laser beam welding process or the electron beam welding process is used to weld the weld, the weld is small, the surface is well formed, the weld quality is excellent, the flash of the weld does not exist in the cooling channel, the cooling oil can smoothly reach the top of the cooling channel, and the piston head is beneficial to cooling; the horizontal and vertical staggered arrangement of the weld can bear the external force received by the skirt, the connecting strength of the inner piston body and the outer piston body is higher, and the service life of the piston is prolonged; the piston head and the pin seat of the inner piston body are an integrated structure penetrating from top to bottom, the probability of fatigue fracture between the pin seat and the piston head is reduced in the long-time use of the piston, and the service life of the piston is prolonged.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine piston technology, and more specifically to a steel piston and its manufacturing process. Background Technology

[0002] In the field of internal combustion engine pistons, steel pistons have become an important direction in piston development and are being used more and more widely. To reduce the temperature of the steel piston head, cooling channels are incorporated into the piston head. Currently, steel pistons commonly use friction welding to form closed cooling channels. However, friction welding inevitably produces burrs within the cooling channels, hindering the smooth flow of cooling oil to the top of the channel and consequently impairing piston head cooling. Furthermore, during the welding process, the weld seam forms a closed ring, with an overlapping area at its start and end. This area is prone to and inevitably contains welding defects, which degrade weld quality. Since the weld seam is located on the piston top surface or in the combustion chamber—high-temperature, high-pressure, and high-load areas—welding defects in the weld seam will reduce piston lifespan and affect the reliable and safe operation of the engine. Summary of the Invention

[0003] The purpose of this invention is to provide a steel piston and its manufacturing process, and to optimize the welding forming process and arrangement to extend the service life of the steel piston.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A steel piston includes an inner piston body and an outer piston body made of steel.

[0006] The inner piston body includes a piston head and a pin seat integrally formed from top to bottom. The upper end of the piston head is recessed inward to form a combustion chamber. An annular inner cooling groove is formed along the circumference of the side of the piston head. The circumference of the side of the piston head is set as an upper annular groove at a position slightly above the outer side of the inner cooling groove. The upper edge end face of the inner cooling groove extends laterally, and the lower edge end face of the inner cooling groove extends vertically.

[0007] The outer piston body includes a lower annular groove and a skirt integrally formed from top to bottom. The upper end face of the lower annular groove extends laterally, and the inner side of the lower annular groove protrudes to form a support portion. The end face of the support portion extends vertically.

[0008] The pin seat passes through the lower annular groove and is embedded inside the skirt. The upper edge end face of the inner cold groove is attached to the upper end face of the lower annular groove to form a first weld and is welded to the first weld. The lower edge end face of the inner cold groove is attached to the end face of the support to form a second weld and is welded to the second weld. The upper annular groove is connected to the lower annular groove to form an annular groove. The inner cold groove is closed to form an inner cold channel.

[0009] Preferably, the pin seat has a piston pin hole along the horizontal direction, and the skirt has a piston pin assembly hole at the position corresponding to the piston pin hole.

[0010] Preferably, the orthographic projection of the skirt is a circle.

[0011] Preferably, the annular groove portion has a plurality of annular banks and annular grooves along its circumferential edge, and the first weld passes through the annular banks, or the annular grooves, or the position below the lowest annular groove.

[0012] Preferably, the first weld and / or the second weld are welded by laser beam welding or electron beam welding.

[0013] Preferably, a gap is left between the pin seat and the outer piston body.

[0014] Preferably, the outer diameter of the skirt is larger than the outer diameters of the upper and lower annular grooves.

[0015] Preferably, the strength of the material used to manufacture the outer piston body does not exceed the strength of the material used to manufacture the inner piston body.

[0016] Preferably, the material used to manufacture the inner piston body is any one of 38MnVS6 alloy steel, 42CrMoA alloy steel, and 42CrMo4 alloy steel.

[0017] The material used to manufacture the outer piston body is any one of 38MnVS6 alloy steel, 42CrMoA alloy steel, and 42CrMo4 alloy steel, or any one of 20CrNiMo alloy steel and 20CrNi3MoTi alloy steel.

[0018] A steel piston manufacturing process for manufacturing the aforementioned steel piston includes the following steps:

[0019] Step 1: The inner piston body and the outer piston body are manufactured and shaped separately;

[0020] Step 2: Pass the pin seat of the inner piston body through the lower ring groove of the outer piston body, embed the pin seat of the inner piston body inside the skirt of the outer piston body, attach the upper edge end face of the inner cold groove of the inner piston body to the upper end face of the lower ring groove of the outer piston body to form the first weld, and attach the lower edge end face of the inner cold groove of the inner piston body to the end face of the support part of the outer piston body to form the second weld.

[0021] Step 3: Weld the first and second welds using laser beam welding or electron beam welding to connect the upper annular groove of the inner piston body with the lower annular groove of the outer piston body to form an annular groove, thereby sealing the inner cold groove and forming an inner cold channel.

[0022] The beneficial technical effects of this invention are:

[0023] The steel piston and manufacturing process of this invention arranges the first weld seam on the side of the annular groove and the second weld seam on the lower side of the cooling groove inside the annular groove. This avoids high-load areas such as the piston top surface and combustion chamber, reducing the impact of welding defects on the piston, greatly extending the piston's service life, and improving the reliability and safety of piston operation. The first and second weld seams are welded using laser beam welding or electron beam welding, resulting in small weld seams, good surface formation, and excellent weld quality. This prevents flash in the cooling channel, allowing the cooling oil to smoothly reach the top of the cooling channel. The inner piston body is designed to facilitate piston head cooling. The skirt is subjected to lateral thrust from the connecting rod, pressure from the cylinder wall, and friction. The first weld extends laterally, and the second weld extends vertically. After the first and second welds are welded separately, their staggered arrangement can withstand the external forces on the skirt, resulting in a stronger connection between the inner and outer piston bodies and extending the piston's service life. The piston head and pin seat of the inner piston body are a single, continuous structure from top to bottom, reducing the likelihood of fatigue fracture between the pin seat and piston head during prolonged piston use and extending the piston's service life. Attached Figure Description

[0024] Figure 1 This is a perspective view of the inner piston body in the steel piston of an embodiment of the present invention;

[0025] Figure 2 This is a perspective view of the outer piston body in the steel piston of an embodiment of the present invention;

[0026] Figure 3 This is a main sectional view of the first weld of the steel piston in an embodiment of the present invention passing through the second ring bank;

[0027] Figure 4 for Figure 3 Sectional view of AA;

[0028] Figure 5 This is a front sectional view of the first weld of the steel piston in an embodiment of the present invention passing through the second annular groove;

[0029] Figure 6 This is a main sectional view of the first weld of the steel piston in an embodiment of the present invention passing through the third ring bank;

[0030] Figure 7 This is a front sectional view of the first weld of the steel piston in an embodiment of the present invention passing through the third annular groove;

[0031] Figure 8 This is a front sectional view of the position where the first weld of the steel piston in an embodiment of the present invention passes through the lower part of the third annular groove. Detailed Implementation

[0032] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Certain embodiments of the invention will be described more fully below with reference to the accompanying drawings, and some, but not all, of these embodiments will be shown. In fact, various embodiments of the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the invention to meet applicable legal requirements.

[0033] In the description of this invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In this embodiment of the invention, a steel piston and its manufacturing process are provided; please refer to [reference needed]. Figures 1 to 8 As shown.

[0035] A steel piston includes an inner piston body and an outer piston body made of steel.

[0036] The inner piston body includes a piston head 11 and a pin seat 12 integrally formed from top to bottom. The upper end of the piston head 11 is recessed inward to form a combustion chamber 2. An annular inner cooling groove 3 is formed along the circumference of the piston head 11. The circumference of the side of the piston head 11 is set as an upper annular groove 41 at a position slightly above the outer side of the inner cooling groove 3. The upper side edge end face 31 of the inner cooling groove extends laterally, and the lower side edge end face 32 of the inner cooling groove extends vertically.

[0037] The outer piston body includes a lower ring groove 42 and a skirt 5 integrally formed from top to bottom. The upper end face 421 of the lower ring groove extends laterally, and the inner side of the lower ring groove 42 protrudes to form a support portion. The end face 422 of the support portion extends vertically.

[0038] The pin seat 12 passes through the lower annular groove 42 and is embedded inside the skirt 5. The upper edge end face 31 of the inner cold groove is attached to the upper end face 421 of the lower annular groove to form a first weld 61 and is welded to the first weld 61. The lower edge end face 32 of the inner cold groove is attached to the end face 422 of the support to form a second weld 62 and is welded to the second weld 62. The upper annular groove 41 is connected to the lower annular groove 42 to form an annular groove. The inner cold groove 3 is closed to form an inner cold channel. The first weld 61 and the second weld 62 are welded by laser beam welding or electron beam welding.

[0039] The piston pin seat 12 has a piston pin hole 121 along the horizontal direction, and the skirt 5 has a piston pin assembly hole 51 corresponding to the position of the piston pin hole 121. When assembling the piston and connecting rod, the piston pin is passed through the piston pin assembly hole 51 to be assembled into the piston pin hole 121.

[0040] The orthographic projection of the skirt 5 is a circle, so that the outer contour of the skirt 5 fits the inner wall of the cylinder.

[0041] The annular groove portions (upper annular groove portion 41 and lower annular groove portion 42) have a plurality of annular banks and annular grooves along their circular periphery. The first weld 61 passes through the annular banks, or the annular grooves, or the position below the lowermost annular groove. Specifically, the annular groove portions have, from top to bottom, a first annular bank 71, a first annular groove 81, a second annular bank 72, a second annular groove 82, a third annular bank 73, and a third annular groove 83. In this embodiment, the first weld 61 passes through any position among the second annular bank 72, the second annular groove 82, the third annular bank 73, the third annular groove 83, and the position below the third annular groove 83.

[0042] A gap is left between the pin seat 12 and the outer piston body to facilitate laser or electron beam welding of the second weld 62 through the gap.

[0043] The outer diameter of the skirt 5 is larger than the outer diameter of the upper ring groove 41 and the lower ring groove 42, so that the skirt 5 contacts the inner wall of the cylinder, while the upper ring groove 41 and the lower ring groove 42 do not contact the inner wall of the cylinder.

[0044] In this embodiment, the piston head 11 and pin seat 12 of the inner piston body are an integral structure that runs from top to bottom, so that the strength of the material used to manufacture the outer piston body does not exceed the strength of the material used to manufacture the inner piston body.

[0045] The inner piston body is made of any one of the following three ultra-high-strength alloy steels: 38MnVS6 alloy steel, 42CrMoA alloy steel, and 42CrMo4 alloy steel. The outer piston body is made of any one of the following three ultra-high-strength alloy steels: 38MnVS6 alloy steel, 42CrMoA alloy steel, and 42CrMo4 alloy steel. Alternatively, the outer piston body can be made of any one of the following lower-strength alloy steels: 20CrNiMo alloy steel and 20CrNi3MoTi alloy steel, to reduce material costs.

[0046] A steel piston manufacturing process for manufacturing the steel piston described in this embodiment includes the following steps:

[0047] Step 1: The inner piston body and the outer piston body are forged and formed separately;

[0048] Step 2: Pass the pin seat 12 of the inner piston body through the lower ring groove 42 of the outer piston body, embed the pin seat 12 of the inner piston body into the skirt 5 of the outer piston body, attach the upper edge end face 31 of the inner cold groove of the inner piston body to the upper end face 421 of the lower ring groove of the outer piston body to form a first weld 61, and attach the lower edge end face 32 of the inner cold groove of the inner piston body to the end face 422 of the support part of the outer piston body to form a second weld 62.

[0049] Step 3: Weld the first weld 61 and the second weld 62 using laser beam welding or electron beam welding, so that the upper ring groove 41 of the inner piston body connects with the lower ring groove 42 of the outer piston body to form a ring groove, and the inner cooling groove 3 is closed to form an inner cooling channel.

[0050] The present embodiment has now been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the steel piston and manufacturing process of the present invention. In the steel piston and manufacturing process of the present invention, the first weld 61 is arranged on the side of the annular groove, and the second weld 62 is arranged on the lower side of the cooling groove 3 within the annular groove. This ensures that the first weld 61 and the second weld 62 avoid high-load areas such as the top surface of the piston and the combustion chamber 2, reducing the impact of welding defects on the piston, greatly extending the piston's service life, and improving the reliability and safety of piston operation. The first weld 61 and the second weld 62 are welded using laser beam welding or electron beam welding, resulting in small welds, good surface formation, and excellent weld quality. This prevents flash in the cooling channel, allowing the cooling oil to smoothly reach the top of the cooling channel, which is beneficial for the piston's operation. The piston head 11 is cooled; the skirt 5 is subjected to the lateral thrust of the connecting rod, the pressure of the cylinder inner wall, and friction. The first weld 61 is arranged in a transverse direction, and the second weld 62 is arranged in a vertical direction. After the first weld 61 and the second weld 62 are welded respectively, the first weld 61 and the second weld 62 are arranged in a cross-sectional manner to withstand the external force on the skirt 5. The connection strength between the inner piston body and the outer piston body is higher, so as to extend the service life of the piston. The piston head 11 and the pin seat 12 of the inner piston body are a through-hole integrated structure from top to bottom. During the long-term use of the piston, the probability of fatigue fracture between the pin seat 12 and the piston head 11 is reduced, so as to extend the service life of the piston.

[0051] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A steel piston, characterized in that: Includes an inner piston body and an outer piston body made of steel; The inner piston body includes a piston head and a pin seat integrally formed from top to bottom. The upper end of the piston head is recessed inward to form a combustion chamber. An annular inner cooling groove is formed along the circumference of the side of the piston head. The circumference of the side of the piston head is set as an upper annular groove at a position slightly above the outer side of the inner cooling groove. The upper edge end face of the inner cooling groove extends laterally, and the lower edge end face of the inner cooling groove extends vertically. The outer piston body includes a lower annular groove and a skirt integrally formed from top to bottom. The upper end face of the lower annular groove extends laterally, and the inner side of the lower annular groove protrudes to form a support portion. The end face of the support portion extends vertically. The pin seat passes through the lower annular groove and is embedded inside the skirt. The upper edge end face of the inner cold groove is attached to the upper end face of the lower annular groove to form a first weld and is welded to the first weld. The lower edge end face of the inner cold groove is attached to the end face of the support to form a second weld and is welded to the second weld. The upper annular groove is connected to the lower annular groove to form an annular groove. The inner cold groove is closed to form an inner cold channel. Wherein, the upper edge end face of the inner cooling groove is the lower end face of the upper annular groove, and the upper edge end face of the inner cooling groove is located below the top of the inner cooling groove; The first weld and / or the second weld are welded by laser beam welding or electron beam welding. A gap is left between the pin seat and the outer piston body, through which the second weld is welded.

2. A steel piston according to claim 1, characterized in that: The pin seat has a piston pin hole in the horizontal direction, and the skirt has a piston pin assembly hole at the position corresponding to the piston pin hole.

3. A steel piston according to claim 2, characterized in that: The orthographic projection of the skirt is a circle.

4. A steel piston according to claim 1, characterized in that: The annular groove portion has several annular banks and annular grooves along its circumferential edge. The first weld passes through the annular banks, or the annular grooves, or the lower part of the lowermost annular groove.

5. A steel piston according to claim 1, characterized in that: The outer diameter of the skirt is greater than the outer diameters of the upper and lower annular grooves.

6. A steel piston according to claim 1, characterized in that: The strength of the material used to manufacture the outer piston body shall not exceed the strength of the material used to manufacture the inner piston body.

7. A steel piston according to claim 6, characterized in that: The material used to manufacture the inner piston body is any one of 38MnVS6 alloy steel, 42CrMoA alloy steel and 42CrMo4 alloy steel. The material used to manufacture the outer piston body is any one of 38MnVS6 alloy steel, 42CrMoA alloy steel, and 42CrMo4 alloy steel, or any one of 20CrNiMo alloy steel and 20CrNi3MoTi alloy steel.

8. A steel piston manufacturing process for manufacturing the steel piston according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: The inner piston body and the outer piston body are manufactured and shaped separately; Step 2: Pass the pin seat of the inner piston body through the lower ring groove of the outer piston body, embed the pin seat of the inner piston body inside the skirt of the outer piston body, attach the upper edge end face of the inner cold groove of the inner piston body to the upper end face of the lower ring groove of the outer piston body to form the first weld, and attach the lower edge end face of the inner cold groove of the inner piston body to the end face of the support part of the outer piston body to form the second weld. Step 3: Weld the first and second welds using laser beam welding or electron beam welding to connect the upper annular groove of the inner piston body with the lower annular groove of the outer piston body to form an annular groove, thereby sealing the inner cold groove and forming an inner cold channel.

Images