Hydraulic stretching device and method for pre-tightening cylinder head nuts of 6G70GI main engine

Abstract

A hydraulic tensioning device and method for pre-tightening cylinder head nuts of a 6G70GI engine includes a hydraulic tensioner and a pressure ring. A circumferential contraction shoulder is provided between the upper and lower portions of the hydraulic tensioner, reducing the diameter of the lower portion to avoid interference with gas components. The pressure ring has a concave arc surface on its side to avoid interference with adjacent cylinder head nuts, and a perforated groove is provided on its bottom to avoid protruding blockages. The pressure ring is inserted into the cylinder head nuts to ensure that it is placed on the cylinder head studs stably and without interference. The hydraulic tensioner is placed on the cylinder head studs, and the cylinder head nuts are tightened after repeated pressure increase and stabilization. The pressure is then reduced to zero and re-increased until a predetermined working pressure is reached. After stabilization, the cylinder head nuts are tightened to complete the pre-tightening of the cylinder head nuts. The present invention effectively avoids interference with gas components while maintaining the strength and safety of the hydraulic tensioner. The cylinder head nuts can be pre-tightened without removing the gas components, thereby improving operating efficiency and ensuring structural airtightness.

Description

Technical Field

[0001] The invention relates to a manufacturing process of a marine engine, in particular to a hydraulic stretching device and method for pre-tightening a nut of a 6G70GI main engine cylinder cover, belonging to the technical field of marine engine manufacturing. Background Art

[0002] The 6G70 GI main engine is a new type of marine low-speed diesel engine that uses high-pressure natural gas as its primary fuel. The gas is externally pressurized to approximately 300 bar, then filled into the cylinder head's gas components and injected into the combustion chamber through the gas valve for combustion. The addition of gas components to the cylinder head's top space has resulted in a more compact structural layout. This has created numerous obstructions, such as plugs, at various heights above and above the cylinder head's top surface, hindering the use of hydraulic tensioners to pretighten the cylinder head nuts. If the existing hydraulic tensioners and pressure rings were still used, the interfering plugs and flanges of the gas components would first need to be removed, and then pretightened using the hydraulic tensioner. After pretightening, the gas components could be reassembled. The removal and reinstallation of gas components during this process could result in air and oil leaks, necessitating re-verification of the airtight structure and complicating the assembly process. Summary of the Invention

[0003] The object of the present invention is to provide a hydraulic stretching device and method for pre-tightening the cylinder head nuts of a 6G70 GI main engine. By optimizing and improving the structure and appearance of the original hydraulic stretcher and pressure ring, interference with the plug and the adjacent cylinder head nuts is avoided. Without removing the relevant gas structural components, the cylinder head nut pre-tightening operation is successfully completed, thereby shortening the installation time, reducing the workload, improving the working efficiency, and ensuring the airtightness and safety of the structure.

[0004] The technical solutions of the present invention are as follows:

[0005] A hydraulic stretching device for pre-tightening the cylinder head nuts of a 6G70GI main engine comprises a hydraulic stretcher and a pressure ring. The cylinder head of the 6G70GI main engine is provided with a gas component including a plug. The device is characterized in that a circumferential shrinkage shoulder is provided between the upper and lower parts of the hydraulic stretcher to reduce the diameter of the lower part to avoid interference with the gas component. The side of the pressure ring is provided with a concave arc surface to avoid interference with adjacent cylinder head nuts. The bottom of the pressure ring is provided with an open hole groove to avoid the protruding plug.

[0006] Furthermore, the upper portion of the hydraulic stretcher is increased in height to maintain the necessary strength of the hydraulic stretching device.

[0007] Furthermore, the number of the opening slots is 2, and the slots are symmetrically distributed.

[0008] Furthermore, the number of the concave arc surfaces is 2, and they are symmetrically distributed.

[0009] Another technical solution of the present invention is:

[0010] A hydraulic stretching method for pre-tightening the cylinder head nut of a 6G70GI main engine, implemented by the above-mentioned hydraulic stretching device, comprises the following steps:

[0011] 1) Insert the pressure ring onto the cylinder head nut. If there is a plug on the cylinder head of the 6G70GI engine, align the opening groove with the plug. If there are other cylinder head nuts adjacent to the cylinder head, align the concave arc surface without contacting the adjacent cylinder head nuts to ensure that the pressure ring is placed on the cylinder head stably and without interference.

[0012] 2) Place the hydraulic tensioner on the cylinder head stud of the 6G70GI main engine and rotate it until it is tightly flush with the pressure ring;

[0013] 3) gradually increasing the pressure of the hydraulic tensioner, pausing to stabilize the pressure, tightening the cylinder head nut, then unloading the pressure of the hydraulic tensioner to zero, and then increasing the pressure again;

[0014] 4) Repeat step 3) repeatedly until the hydraulic tensioner reaches a predetermined working pressure, tighten the cylinder head nut after the pressure is stabilized, and then release the pressure and remove the hydraulic tensioning device, thereby completing the pre-tightening of the cylinder head nut.

[0015] Compared with the prior art, the technical advantages of the present invention are as follows:

[0016] In view of the difficulty that the original hydraulic stretching device cannot adapt to the pre-tightening operation of the cylinder head nuts of the 6G70 GI type main engine, the present invention improves its structure and appearance. By providing an open hole groove at the bottom of the pressure ring, the pressure ring can avoid being blocked by the raised surface on the cylinder head. A concave arc surface is provided on the side of the pressure ring to avoid interference with the adjacent cylinder head nuts. By shrinking the non-main force-bearing structure at the bottom of the hydraulic stretcher, interference with gas components is avoided. At the same time, the height of the upper part is thickened to achieve the requirements of not affecting strength and safety.

[0017] In summary, the present invention effectively avoids interference with the gas components on the cylinder head while maintaining the strength and safety of the entire hydraulic stretching device. Without removing the relevant gas structural components, the cylinder head nut pre-tightening operation is successfully completed, achieving the effect of facilitating installation and use, improving work efficiency, and ensuring structural air tightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the hydraulic stretching device of the present invention.

[0019] Figure 2 yes Figure 1 AA cross-sectional view.

[0020] Figure 3 This is one of the working state diagrams of the present invention.

[0021] Figure 4 This is the second working state diagram of the present invention.

[0022] In the figure,

[0023] 01-cylinder head nut, 02-blocking plug, 1-hydraulic stretcher, 11-shrinkage shoulder, 2-pressure ring, 21-opening groove, 22-concave arc surface. DETAILED DESCRIPTION

[0024] The hydraulic tensioner and the method of use of the present invention are further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection claimed in the present invention is not limited thereby.

[0025] The present invention is used for pre-tightening the cylinder head nuts of a 6G70GI main engine; the upper plane of the cylinder head of the 6G70GI main engine and the space above it are provided with gas components, including a raised plug, which hinders the operation of pre-tightening the cylinder head nuts using a hydraulic tensioner.

[0026] The present invention improves the structure and appearance of the original hydraulic stretching device. Figure 1 and Figure 2 The hydraulic stretching device includes a hydraulic stretcher 1 and a pressure ring 2. The lower pressure ring 2 transmits the tensile force on the cylinder head studs to the cylinder head. The upper hydraulic stretcher 1 has a hydraulic cylinder on the outside and a hydraulic piston on the inside. Hydraulic oil is injected into the cavity between the two to push the hydraulic piston upward, thereby stretching the cylinder head studs and pre-tightening the cylinder head nuts.

[0027] See also Figure 1 Considering the relative positions of the flanges on both sides of the gas valve and the cylinder head nuts, the hydraulic cylinder structure at the bottom of the hydraulic tensioner 1 is designed to be contracted where it does not affect strength. A circumferential contraction shoulder 11 is provided between the upper and lower parts of the hydraulic tensioner 1 to reduce the diameter of the lower part to avoid interference with the gas components. The thin-walled structure at the top of the hydraulic tensioner 1 is thickened and increased in height to avoid a decrease in the hydraulic cylinder's strength and safety.

[0028] Considering the maximum size of the plug, the bottom of the pressure ring 2 is designed with an opening groove 21. Since the main pressure here has little effect on the strength, in order to avoid the protruding plug, the opening position is rounded to reduce stress concentration. Figure 1The number of opening slots 21 is 2 and the positions can be symmetrically distributed. Considering the position of the adjacent cylinder head nuts, an arc-shaped contraction design is performed on both sides of the side of the pressure ring 2 in a symmetrical direction, and a concave arc surface 22 is provided, such as Figure 2 , thereby avoiding interference between the pressure ring 2 and the adjacent cylinder head nut, see Figure 4 , and make allowance design to avoid interference caused by position deviation. The number of the concave arc surface 22 is 2, and the positions are symmetrically distributed.

[0029] The hydraulic stretching method implemented by the hydraulic stretching device is as follows:

[0030] Please refer to Figure 3 and Figure 4 First, insert the pressure ring 2 into the cylinder head nut 01, and make sure that the pressure ring 2 is placed stably. When there is a blockage at the bottom, the pressure ring 2 should be rotated until the opening groove 21 is aligned with the blockage 02 to cross over and avoid interference. When used at the front and rear ends, the concave arc surface 22 should be aligned with the adjacent cylinder head nut 01. Secondly, place the hydraulic tensioner 1 on the cylinder head stud and rotate it until it is tightly flush with the pressure ring 2. Again, gradually increase the pressure in multiple times, and tighten the cylinder head nut 01 at each pause to stabilize the pressure, then relieve the pressure to zero and increase the pressure again. Finally, after the hydraulic tensioner 1 reaches the predetermined working pressure, stabilize the pressure and tighten the cylinder head nut 01, relieve the pressure and remove the hydraulic tensioner 1 and the pressure ring 2, thereby completing the pre-tightening of the cylinder head nut 01.

[0031] In summary, the present invention completes the pre-tightening of the cylinder head nuts without dismantling the gas-related structures, while ensuring that the strength and safety of the structure are not reduced, improving work efficiency, saving manpower, and reducing work intensity.

Claims

1. A hydraulic stretching method for pre-tightening the cylinder head nuts of a 6G70GI engine, implemented using a hydraulic stretching device comprising a hydraulic stretcher and a pressure ring. The cylinder head of the 6G70GI engine is provided with a gas component including a plug, and is characterized by: A circumferential shrinkage shoulder is provided between the upper and lower parts of the hydraulic tensioner to reduce the diameter of the lower part to avoid interference with the gas components. The side of the pressure ring is provided with a concave arc surface to avoid interference with the adjacent cylinder head nut. The bottom of the pressure ring is provided with an open hole groove to avoid bulging blockage. The hydraulic stretching method comprises the following steps: 1) Insert the pressure ring onto the cylinder head nut. If there is a plug on the cylinder head of the 6G70GI engine, align the opening groove with the plug. If there are other cylinder head nuts adjacent to the cylinder head, align the concave arc surface without contacting the adjacent cylinder head nuts to ensure that the pressure ring is placed on the cylinder head stably and without interference. 2) Place the hydraulic tensioner on the cylinder head stud of the 6G70GI main engine and rotate it until it is tightly flush with the pressure ring; 3) gradually increasing the pressure of the hydraulic tensioner, pausing to stabilize the pressure and then tightening the cylinder head nut, then reducing the pressure of the hydraulic tensioner to zero and increasing the pressure again; 4) Repeat step 3) repeatedly until the hydraulic tensioner reaches a predetermined working pressure, tighten the cylinder head nut after the pressure is stabilized, then release the pressure and remove the hydraulic tensioning device, thereby completing the pre-tightening of the cylinder head nut.

2. The hydraulic stretching method for pre-tightening the cylinder head nut of a 6G70GI main engine according to claim 1, characterized in that: The upper portion of the hydraulic stretcher is increased in height to maintain the necessary strength of the hydraulic stretching device.

3. The hydraulic stretching method for pre-tightening the cylinder head nut of a 6G70GI main engine according to claim 1, characterized in that: There are two opening slots, which are symmetrically distributed.

4. The hydraulic stretching method for pre-tightening the cylinder head nut of a 6G70GI main engine according to claim 1, characterized in that: There are two concave arc surfaces, which are symmetrically distributed.

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