Tooling and fixing methods for machining diesel engine piston skirts

Abstract

This disclosure relates to a machining fixture and fixing method for a diesel engine piston skirt. The machining fixture includes: a clamping plate with a second through hole, which is positioned at a first end of the piston skirt; a positioning plate with a third through hole, which is positioned at a second end of the piston skirt; a mandrel with a stepped portion, which extends from the third through hole of the positioning plate into a cavity and passes through the first and second through holes, and the stepped portion abuts against the positioning plate; threaded portions are provided on the ends of the mandrel extending from the first and third through holes, and the clamping plate is threadedly connected to the threaded portions of the mandrel extending from the first through hole through the second through hole; a pull rod hole is provided on the mandrel; a tensioning assembly is threadedly connected to the threaded portion of the mandrel extending from the third through hole, and the tensioning assembly is configured to apply a hydraulic tensioning force to the mandrel; a pull rod is inserted into the pull rod hole, and both ends of the pull rod are located in two pin holes. This design ensures that both the pin holes and the contact surface at the top of the piston skirt are subjected to force, increasing the stress-bearing areas of the piston skirt.

Description

Technical Field

[0001] This disclosure relates to the field of machining technology, and more specifically, to a cutting tooling for a diesel engine piston skirt and a method for fixing the diesel engine piston skirt. Background Technology

[0002] Currently, the piston of a marine diesel engine is a key component for transmitting power and motion. Together with the cylinder head and cylinder liner, it forms the combustion chamber of the diesel engine. It is connected to the piston through the piston pin and converts the linear motion obtained by the piston after the combustion gas explosion into the rotational motion of the crankshaft through the connecting rod.

[0003] Pistons operate in harsh environments and are prone to cracking. Most of these cracks originate during the manufacturing process, making the quality of machining directly impact the performance of diesel engines. Diesel engine pistons are characterized by complex structures, thin walls, and poor radial rigidity, making them susceptible to significant machining deformation, particularly along the major and minor axes. This deformation directly affects the friction between the piston skirt and the cylinder liner.

[0004] An improper piston skirt clamping position results in uneven clamping force on the piston skirt. Areas with poor rigidity will experience greater deformation during processing, or stress concentration may occur in certain areas, which may lead to plastic deformation in severe cases. Therefore, it is necessary to propose improvements.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this disclosure is to provide a machining fixture for piston skirts and a method for fixing piston skirts, so that the pin holes of piston skirts and the contact surfaces between the skirt and the top are subjected to force, thereby increasing the force-bearing parts of the piston skirt.

[0007] According to one aspect of this disclosure, a machining fixture for a piston skirt is provided. The piston skirt includes a first end and a second end, the piston skirt being connected to a piston top via the first end. The first end has a first through hole, and an open cavity is formed from the second end toward the first end. The piston skirt has symmetrically distributed pin holes between the first end and the second end, communicating with the cavity. The machining fixture includes:

[0008] A clamping plate, including a second through hole, the clamping plate being disposed at the first end of the piston skirt, the second through hole being a threaded hole;

[0009] A positioning plate, including a third through hole, is used to be disposed at the second end of the piston skirt;

[0010] The mandrel includes a stepped portion, which extends into the cavity through the third through hole of the positioning plate and passes through the first through hole and the second through hole. The stepped portion abuts against the positioning plate. The ends of the mandrel extending from the second through hole and the third through hole are respectively provided with threaded portions. The clamping plate is threadedly connected to the threaded portions of the mandrel extending from the first through hole through the second through hole. The mandrel is provided with a pull rod hole.

[0011] A tensioning assembly for threaded connection with the threaded portion of the mandrel extending from the third through hole, the tensioning assembly being configured to apply a hydraulic tensioning force to the mandrel;

[0012] A pull rod is used to insert into the pull rod hole, and the two ends of the pull rod are respectively located in the two pin holes.

[0013] In one exemplary embodiment of this disclosure, the positioning disk further includes:

[0014] The positioning protrusion extends into the cavity and abuts against the inner wall of the cavity when the piston skirt abuts against the positioning disk, thus limiting the radial movement of the piston skirt.

[0015] In one exemplary embodiment of this disclosure, the positioning disk is provided with a plurality of positioning protrusions, which are evenly distributed in the circumferential direction of the positioning disk.

[0016] In one exemplary embodiment of this disclosure, the positioning disk further includes:

[0017] Positioning holes;

[0018] A positioning pin is provided on the positioning hole.

[0019] In one exemplary embodiment of this disclosure, the tensioning assembly is a hydraulic tensioning assembly.

[0020] In one exemplary embodiment of this disclosure, the through hole of the clamping disc is provided with a boss on one side and a recess on the other side.

[0021] In one exemplary embodiment of this disclosure, the diameter of the clamping disc is less than or equal to the end face diameter of the first end of the piston skirt.

[0022] In one exemplary embodiment of this disclosure, the pull rod is cylindrical.

[0023] According to another aspect of this disclosure, a method for fixing a piston skirt is provided. The piston skirt includes a first end and a second end, the piston skirt being connected to a piston top via the first end. The first end has a first through hole, and an open cavity is formed from the second end toward the first end. The piston skirt has symmetrically distributed pin holes between the first end and the second end, communicating with the cavity. The fixing method includes:

[0024] Provide the cutting tooling described in any of the above embodiments;

[0025] Insert the mandrel into the third through hole of the positioning plate, sleeve the piston skirt on the mandrel through the first through hole, and make the second end of the piston skirt abut against the positioning plate, thread the clamping plate onto the mandrel through the second through hole, and insert the pull rod into the pull rod hole;

[0026] The tensioning assembly is threaded to the end of the mandrel located at the second end, and a preset tension is applied to the end of the mandrel through the tensioning assembly so that the pull rod fits against the inner wall of the pin hole to generate an initial preload.

[0027] The tensioning assembly applies a further tension to the end of the mandrel, causing the pull bar to fit against the inner wall of the pin hole and generate a preset preload.

[0028] In one exemplary embodiment of this disclosure, the axial force generated when the pressure plate is tightened is less than the preset tension applied to the mandrel by the tensioning assembly.

[0029] The piston skirt machining fixture disclosed herein ensures that the pin hole and the contact surface between the skirt and the top of the piston skirt are all stressed, increasing the stress-bearing areas of the piston skirt. This prevents the stress from being concentrated in a single location during clamping and increases the effective stress area, thus improving the problem of large deformation of the piston skirt's long axis, short axis, and profile during machining, thereby improving machining quality and reducing machining costs. A threaded portion extends from the mandrel, increasing the effective area of ​​the clamping nut and reducing stress concentration through the clamping plate. During clamping, the mandrel passes through the positioning plate, with a clearance fit between the mandrel and the positioning plate. The piston skirt is placed horizontally, allowing the mandrel to exit through the first through hole in the piston skirt's inner cavity. After the piston skirt is positioned, a pull rod is passed through the pin hole of the piston skirt and the pull rod hole of the mandrel. The machine tool's hydraulic tensioning system is activated, applying a small pulling force to initially create a small contact between the pull rod and the piston pin hole, generating initial preload. Next, screw the clamping coil onto the mandrel. The torque applied during tightening should not be too large; the resulting axial force should be less than the tension applied to the mandrel by the hydraulic tensioning system. After pre-tightening, increase the tension of the machine tool's hydraulic tensioning system to the required clamping value to complete the clamping process. This improves the handling of stress concentration, localized plastic deformation, and clamping deformation due to insufficient rigidity during clamping, thus playing a positive role in reducing machining errors in subsequent processing steps.

[0030] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0032] Figure 1 A schematic diagram of a piston skirt provided for one embodiment of this disclosure;

[0033] Figure 2 A schematic diagram of a piston skirt provided for one embodiment of this disclosure;

[0034] Figure 3 A schematic diagram of a piston skirt provided for another embodiment of this disclosure;

[0035] Figure 4 A schematic diagram of a piston skirt provided for another embodiment of this disclosure;

[0036] Figure 5 for Figure 2 The piston skirt shown is a bottom view;

[0037] Figure 6 for Figure 5 A cross-sectional view of the AA plane;

[0038] Figure 7 A schematic diagram of a machining fixture for a piston skirt provided in one embodiment of this disclosure;

[0039] Figure 8 A rear view of a positioning disk provided for one embodiment of this disclosure;

[0040] Figure 9 A front view of the positioning disk provided in one embodiment of this disclosure;

[0041] Figure 10 A side view of a positioning disk provided for one embodiment of this disclosure;

[0042] Figure 11 A front view of a mandrel provided in one embodiment of this disclosure;

[0043] Figure 12 A top view of a mandrel provided in one embodiment of this disclosure;

[0044] Figure 13 A right view of a mandrel provided for one embodiment of this disclosure;

[0045] Figure 14 A front view of a pull rod provided according to an embodiment of this disclosure;

[0046] Figure 15 A right view of a pull rod provided for one embodiment of this disclosure;

[0047] Figure 16 A front view of a clamping disc provided in one embodiment of this disclosure;

[0048] Figure 17 A right view of a clamping disc provided for one embodiment of this disclosure;

[0049] Figure 18 for Figure 16 A cross-sectional view of the BB plane. Detailed Implementation

[0050] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0051] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples shown in the accompanying drawings. It is understood that if the device of the icon is flipped upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0052] The terms “a,” “one,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first,” “second,” and “third,” etc., are used only as markers and are not a limitation on the number of objects.

[0053] The inventors discovered, through finite element analysis, that the two existing clamping schemes have drawbacks. For the bolt preload structure, when the piston skirt is fully compressed, the load applied by the clamping bolts is mainly concentrated at the contact surface between the piston top and the piston skirt. Compared to the overall volume of the piston, this contact area is much smaller, easily leading to stress concentration and causing localized plastic deformation during cutting. For the drawbar structure, when the lathe hydraulic system tightens the drawbar, the piston's load is mainly concentrated in the area from the pin hole to the stop, while the area from the pin hole to the bottom surface of the piston skirt is unloaded. Due to insufficient radial rigidity of the piston, the unloaded portion is prone to significant deformation during machining. Furthermore, in this clamping structure, the contact surface between the drawbar and the piston skirt is only the portion where the outer diameter of the drawbar is tangent to the inner diameter of the pin hole. The main load-bearing area is concentrated in the pin hole, resulting in a small load-bearing area and high localized stress levels.

[0054] To address the aforementioned technical problems, this disclosure provides a machining fixture for piston skirts, such as... Figures 1-6 As shown, the piston skirt 10 includes a first end 110 and a second end 120. The piston skirt 10 is connected to the piston top through the first end 110. The first end 110 has a first through hole 130, and an open cavity is formed from the second end 120 toward the first end 110. The piston skirt 10 has symmetrically distributed pin holes 140 that communicate with the cavity between the first end 110 and the second end 120. Figure 1 , Figure 2 , Figure 5 and Figure 6 The piston skirts shown are of the same model. Figure 3 and Figure 4 The image shown is of another model of piston skirt.

[0055] like Figure 7 As shown, the cutting tooling includes: a clamping plate 50, a positioning plate 20, a mandrel 30, a tensioning assembly, and a pull bar 40. The clamping plate 50 includes a second through hole 510, which is a threaded hole, and is positioned at the first end 110 of the piston skirt 10. The positioning plate 20 includes a 210 and is positioned at the second end 120 of the piston skirt 10. The mandrel 30 includes a stepped portion 320, which extends from the 210 of the positioning plate 20 into the cavity and passes through the first through hole 130 and the second through hole 510. The stepped portion 320 abuts against the positioning plate 20. The mandrel 30 extends from the second through hole 510 into the cavity of the positioning plate 20. The protruding ends of holes 510 and 210 are respectively provided with threaded portions. The clamping plate 50 is threadedly connected to the threaded portion of the spindle 30 protruding from the first through hole 130 through the second through hole 510. The spindle 30 is provided with a pull rod hole 310. The tensioning assembly is used to be threadedly connected to the end of the spindle 30 protruding from 210. The tensioning assembly is configured to apply a hydraulic tensioning force to the spindle 30. The pull rod 40 is used to be inserted into the pull rod hole 310. The two ends of the pull rod 40 are respectively located in two pin holes 140.

[0056] The piston skirt machining fixture disclosed herein ensures that the pin hole 140 of the piston skirt 10 and the contact surface between the skirt and the top are both subjected to force, increasing the force-bearing areas of the piston skirt 10. This prevents the force-bearing area of ​​the piston skirt 10 from being concentrated in a single location during clamping and increases the effective force-bearing area, thus improving the problem of large deformation of the long axis, short axis, and skirt profile during machining, thereby improving machining quality and reducing machining costs. A threaded portion extends from the mandrel 30, and through the clamping plate 50, the effective area of ​​the clamping nut is increased, reducing stress concentration. During clamping, the mandrel 30 passes through the positioning plate 20, with a clearance fit between the mandrel 30 and the positioning plate 20. The piston skirt 10 is placed horizontally, allowing the mandrel 30 to exit through the first through hole 130 inside the piston skirt 10 cavity. After the piston skirt 10 is positioned, the pull rod 40 is passed through the pin hole 140 of the piston skirt 10 and the pull rod hole 310 of the mandrel 30. The machine tool's hydraulic tensioning system is activated to apply a small tension force, initially allowing the pull rod 40 to make slight contact with the piston pin hole 140, generating initial pre-tightening. Then, the clamping plate 50 is screwed onto the mandrel 30. The torque applied during tightening should not be too large; the resulting axial force should be less than the tension force applied to the mandrel 30 by the hydraulic tensioning system. After pre-tightening, the tension force of the machine tool's hydraulic tensioning system is increased to the required clamping force value to complete the clamping. This improves the stress concentration, localized plastic deformation, and clamping deformation caused by insufficient rigidity that occur during clamping, playing a positive role in reducing machining errors in subsequent processing steps.

[0057] In one embodiment of this disclosure, such as Figure 1 and Figure 2As shown, the piston skirt 10 includes a first end 110 and a second end 120. The piston skirt 10 is connected to the piston top through the first end 110. The first end 110 is provided with a first through hole 130, and an open cavity is formed from the second end 120 toward the first end 110. The piston skirt 10 is cylindrical, and the piston skirt 10 has symmetrically distributed pin holes 140 that communicate with the cavity between the first end 110 and the second end 120.

[0058] In one embodiment of this disclosure, such as Figure 3 and Figure 4 As shown, the piston skirt 10 includes a first end 110 and a second end 120. The piston skirt 10 is connected to the piston top through the first end 110. The first end 110 is provided with a first through hole 130, and an open cavity is formed from the second end 120 toward the first end 110. The piston skirt 10 is elliptical, and the piston skirt 10 has symmetrically distributed pin holes 140 that communicate with the cavity between the first end 110 and the second end 120.

[0059] The piston skirt 10 is connected to the piston top to form a piston, which can be a high-power marine diesel engine piston.

[0060] In one embodiment of this disclosure, such as Figures 8-10 As shown, the positioning disk 20 also includes a positioning protrusion 220. When the piston skirt 10 abuts against the positioning disk 20, the positioning protrusion 220 extends into the cavity and abuts against the inner wall of the cavity, thus limiting the radial movement of the piston skirt 10. The positioning disk 20 has multiple positioning protrusions 220, which are evenly distributed circumferentially on the piston skirt 10.

[0061] In one embodiment of this disclosure, such as Figures 8-10 As shown, the positioning disk 20 also includes a positioning hole 240 and a positioning pin 250, with the positioning pin 250 disposed on the positioning hole 240.

[0062] The main function of the positioning plate 20 is to position the piston skirt 10 in the correct position. Its center plate 210 and spindle 30 are in clearance fit. The upper and lower arc-shaped bosses 520 (positioning protrusions 220) provide end face support, and the left and right bosses 230 provide side support. The small hole in the left boss 230 is the positioning hole 240 for the positioning pin 250. The specific dimensions and positions of each boss 520 and boss 230 depend on the actual piston skirt 10 being machined; this disclosure does not impose any limitations on this.

[0063] In one embodiment of this disclosure, the tensioning assembly is a hydraulic tensioning assembly, such as... Figures 11-13As shown, both the left and right ends of the mandrel 30 are threaded. The thread on the left end connects to the machine tool's hydraulic tensioning system, and the thread on the right end connects to the pressure plate 50. The length L of the mandrel 30 is L_1 + L_2. The length of L1 must ensure that the left arc of the pull bar hole 310 when the mandrel 30 is not tensioned is tangent to the left arc of the positioning hole 240 when the piston skirt 10 is installed. The length of L2 is required to extend beyond the center hole (first through hole 130) of the piston cavity to facilitate the installation and removal of the pressure plate 50.

[0064] In one embodiment of this disclosure, such as Figure 14 and Figure 15 As shown, the pull rod 40 is cylindrical and passes through the pin hole 140 of the piston skirt 10 and the pull rod hole 310 of the spindle 30. It is a connecting component for the hydraulic tensioning system to tighten the piston.

[0065] In one embodiment of this disclosure, such as Figures 16-18 As shown, the clamping plate 50 has a boss 520 on one side of the through hole and a recess on the other side. Depending on the object being clamped, the piston skirt 10 has a protruding conical horn hole at the top, so the middle of the clamping plate 50 is recessed to avoid clamping damage to the protruding conical horn hole during clamping.

[0066] The diameter of the clamping plate 50 is less than or equal to the end face diameter of the first end of the piston skirt 10. The diameter of the clamping plate 50 is as close as possible to the end face diameter of the first end of the piston skirt 10 to ensure sufficient contact area. Of course, the diameter of the clamping plate 50 can also be larger than the end face diameter of the first end of the piston skirt 10, and this disclosure does not impose any restrictions on this.

[0067] Embodiments of this disclosure also provide a method for fixing a diesel engine piston skirt. The piston skirt includes a first end and a second end. The piston skirt is connected to the piston top through the first end. The first end has a first through hole, and an open cavity is formed from the second end toward the first end. The piston skirt has symmetrically distributed pin holes that communicate with the cavity between the first end and the second end. The fixing method includes:

[0068] Step S100: Provide the cutting tooling described above;

[0069] Step S200: Insert the mandrel into the third through hole of the positioning plate, put the piston skirt on the mandrel through the first through hole, and make the second end of the piston skirt abut against the positioning plate. Connect the clamping plate to the mandrel through the second through hole and insert the pull rod into the pull rod hole.

[0070] Step S300: Thread the tensioning assembly to the end of the spindle located at the second end, and apply a preset tension to the end of the spindle located at the second end through the tensioning assembly, so that the pull rod fits against the inner wall of the pin hole to generate an initial preload.

[0071] Step S400: Apply a further tension to the end of the mandrel by using the tensioning assembly to make the pull rod fit against the inner wall of the pin hole to generate a preset preload.

[0072] The piston skirt fixing method disclosed herein ensures that the pin hole and the contact surface between the skirt and the top of the piston skirt are both stressed, increasing the stress-bearing areas of the piston skirt. This prevents the stress from being concentrated in a single location during clamping and increases the effective stress area, thus improving the problem of large deformation of the piston skirt's long axis, short axis, and skirt profile during machining, thereby improving machining quality and reducing machining costs. During clamping, the mandrel passes through the positioning plate, with a clearance fit between the mandrel and the positioning plate. The piston skirt is placed horizontally, allowing the mandrel to exit through the first through hole in the piston skirt's inner cavity. After the piston skirt is positioned, a pull rod is passed through the pin hole of the piston skirt and the pull rod hole of the mandrel. The machine tool's hydraulic tensioning system is activated, applying a small pulling force to initially create a small contact between the pull rod and the piston pin hole, generating initial pre-tightening. Then, the clamping disc is screwed onto the mandrel. The torque applied during tightening should not be too large, and the resulting axial force should be less than the pulling force applied to the mandrel by the hydraulic tensioning system. After pre-tightening, the tension of the machine tool's hydraulic tensioning system is increased to the required clamping value to complete the clamping process. This improves the stress concentration, localized plastic deformation, and clamping deformation caused by insufficient rigidity that occur during clamping, and plays a positive role in reducing machining errors in subsequent machining processes.

[0073] The axial force generated when tightening the clamping disc 50 is less than the preset tension applied to the spindle 30 by the tensioning assembly. After pre-tightening, the tension of the machine tool hydraulic tensioning system is increased to the required clamping value to complete the clamping.

[0074] This disclosure takes into account the characteristics of large marine diesel engine pistons, such as thin walls, insufficient radial stiffness, and large outer diameter. Based on actual machining and finite element simulation, the original cutting tooling and piston skirt are analyzed, and the original clamping method is improved. This improves the stress concentration, local plastic deformation and clamping deformation caused by insufficient rigidity that occur during clamping, and plays a positive role in reducing the machining error of subsequent machining processes.

[0075] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A machining fixture for a diesel engine piston skirt, the piston skirt comprising a first end and a second end, the piston skirt being connected to a piston top via the first end, the first end having a first through hole, and an open cavity forming from the second end toward the first end; the piston skirt having symmetrically distributed pin holes between the first end and the second end communicating with the cavity; characterized in that, The cutting tooling includes: A clamping plate, including a second through hole, the clamping plate being disposed at the first end of the piston skirt, the second through hole being a threaded hole; A positioning plate, including a third through hole, is used to be disposed at the second end of the piston skirt; The mandrel includes a stepped portion, which extends into the cavity from the third through hole of the positioning plate and passes through the first through hole and the second through hole. The stepped portion abuts against the positioning plate. The ends of the mandrel extending from the first through hole and the third through hole are respectively provided with threaded portions. The clamping plate is threadedly connected to the threaded portions of the mandrel extending from the first through hole through the second through hole. The mandrel is provided with a pull rod hole. A tensioning assembly for threaded connection with the threaded portion of the mandrel extending from the third through hole, the tensioning assembly being configured to apply a hydraulic tensioning force to the mandrel; A pull rod is used to insert into the pull rod hole, and the two ends of the pull rod are respectively located in the two pin holes.

2. The cutting tooling according to claim 1, characterized in that, The positioning disk also includes: The positioning protrusion extends into the cavity and abuts against the inner wall of the cavity when the piston skirt abuts against the positioning disk, thus limiting the radial movement of the piston skirt.

3. The cutting tooling according to claim 2, characterized in that, The positioning disk is provided with multiple positioning protrusions, which are evenly distributed in the circumferential direction of the positioning disk.

4. The cutting tooling according to claim 1, characterized in that, The positioning disk also includes: Positioning holes; A positioning pin is provided on the positioning hole.

5. The cutting tooling according to claim 1, characterized in that, The tensioning assembly is a hydraulic tensioning assembly.

6. The cutting tooling according to claim 1, characterized in that, The pressure plate has a boss on one side of the through hole and a recess on the other side.

7. The cutting tooling according to claim 1, characterized in that, The diameter of the pressure plate is less than or equal to the end face diameter of the first end of the piston skirt.

8. The cutting tooling according to claim 1, characterized in that, The pull rod is cylindrical.

9. A method for fixing a piston skirt of a diesel engine, the piston skirt comprising a first end and a second end, the piston skirt being connected to a piston top via the first end, the first end having a first through hole, and an open cavity forming from the second end toward the first end; the piston skirt having symmetrically distributed pin holes between the first end and the second end communicating with the cavity; characterized in that, The fixing method includes: Provide a cutting tooling as described in any one of claims 1-8; Insert the mandrel into the third through hole of the positioning plate, sleeve the piston skirt on the mandrel through the first through hole, and make the second end of the piston skirt abut against the positioning plate, thread the clamping plate onto the mandrel through the second through hole, and insert the pull rod into the pull rod hole; The tensioning assembly is threaded to the end of the mandrel located at the second end, and a preset tension is applied to the end of the mandrel through the tensioning assembly so that the pull rod fits against the inner wall of the pin hole to generate an initial preload. The tensioning assembly applies a further tension to the end of the mandrel, causing the pull bar to fit against the inner wall of the pin hole and generate a preset preload.

10. The fixing method according to claim 9, characterized in that, The axial force generated when the pressure plate is tightened is less than the preset tension applied to the mandrel by the tensioning assembly.

Images