Split type aero-engine crankshaft and press fitting method thereof

Abstract

A split type aero-engine crankshaft is composed of a left crank, a right crank and at least one expansion assembly, and the left crank and the right crank are provided with first main journals and first connecting rod journals; the expanding assembly comprises a pair of expanding cranks, a pair of crank discs, a connecting sleeve and a rolling bearing, each crank disc is provided with two pin holes, and each expanding crank is provided with a second main journal and a second connecting rod journal; external splines are arranged on the second main journals, internal splines are arranged in the connecting sleeves, and the connecting sleeves are used for positioning and connecting the second main journals on the pair of expanding cranks; the rolling bearing is installed on the connecting sleeve and used for supporting the second main journal. According to the split type crankshaft, the configuration number of the cranks can be increased or decreased at will through the expansion assembly, the machining difficulty and the manufacturing cost of the crankshaft are greatly reduced, and the problem that the main journals are prone to abrasion is fundamentally solved. According to the crankshaft press-fitting method, the coaxiality and the dislocation angle between the cranks can be guaranteed, and the qualification rate of the crankshafts is greatly increased.

Description

Technical Field

[0001] The invention relates to the technical field of aeroengines, and in particular to a split aeroengine crankshaft and a press-assembly method thereof. Background Art

[0002] The piston aircraft engine is mainly composed of crankshaft, connecting rod, piston, cylinder, air distributor and casing, among which the cylinders are mostly arranged in horizontal opposition. At present, the common horizontally opposed aircraft engines include opposed four-cylinder, opposed six-cylinder and opposed eight-cylinder. The crankshaft in each aircraft engine needs to match the layout of the cylinders. The more cylinders there are, the more cranks the crankshaft has.

[0003] Most of the existing multi-crank crankshafts adopt the production process of integral forging, which is difficult to process and has high manufacturing costs. Especially as the number of cranks increases, the coaxiality and misalignment angles between the cranks are difficult to guarantee, and the qualified rate of the finished product is low, resulting in an exponential increase in production costs. In addition, the main journal of the multi-crank crankshaft can only be supported by a split bearing, which is a sliding bearing and is only suitable for medium and low-speed engines. Aircraft engines are high-speed engines. During operation, in addition to the easy wear of the bearing, the abrasive particles dropped from the bearing will also cause rapid wear of the main journal. Therefore, if the multi-crank crankshaft is produced by integral forging, it will not only increase the manufacturing cost of the crankshaft exponentially, but also cause premature wear of the main journal.

[0004] There are also a small number of aircraft engine crankshafts that use a split connection method. The application problems they have are also that the coaxiality and misalignment angles between the cranks are difficult to ensure, and the qualified rate of the finished products is low. Summary of the invention

[0005] In order to overcome the shortcomings of the background technology, the present invention discloses a split aircraft engine crankshaft and a press-fitting method thereof, the purpose of which is:

[0006] 1. Reduce the processing difficulty and manufacturing cost of multi-crank crankshafts;

[0007] 2. Replace the bearing shell to realize the installation of rolling bearing on the crankshaft and solve the wear problem of the main journal;

[0008] 3. Ensure the coaxiality and misalignment angle between the cranks to improve the yield rate.

[0009] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0010] A split aircraft engine crankshaft consists of a left crank, a right crank and at least one expansion component, wherein the left crank and the right crank have a first main journal and a first connecting rod journal; the expansion component includes a pair of expansion cranks, a pair of crank plates, a connecting sleeve and a rolling bearing, wherein the crank plate has two pin holes, and the expansion crank has a second main journal and a second connecting rod journal; an external spline is provided on the second main journal, with the second main journal as the axis, and the keyway of the external spline has a certain angle relationship with the second connecting rod journal; an internal spline is provided in the connecting sleeve, and the connecting sleeve is used to position and connect the second main journals on a pair of expansion cranks; the rolling bearing is installed on the connecting sleeve to support the second main journal.

[0011] After implementing the above technical solution, compared with the background technology, the beneficial effects produced are:

[0012] 1. The number of crank configurations can be increased or decreased at will through expansion components to meet the needs of various models;

[0013] 2. The expansion components are universal parts. By combining the expansion components, the processing difficulty and manufacturing cost of multi-crank crankshafts can be greatly reduced;

[0014] 3. The installation of rolling bearings on the crankshaft is realized. Rolling bearings have the advantages of high speed, low friction and long service life. The wear surface is limited to the rolling elements and the inner and outer ring tracks, which fundamentally solves the problem of easy wear of the main shaft neck.

[0015] To further improve the technical solution, there are two rolling bearings, and the expansion component also includes a spacer sleeve, which is arranged between the two rolling bearings and is provided with an oil inlet hole and an oil groove.

[0016] After the above technical solution is implemented, the beneficial effects are as follows: the two rolling bearings can increase the total bearing capacity of the main journal, the spacer can separate the two rolling bearings, and the two rolling bearings can be axially limited. In addition, a lubrication system is provided on the casing, and the lubricating oil enters the rolling bearing through the oil inlet hole and the oil groove to achieve lubrication of the rolling bearing.

[0017] To further improve the technical solution, the rolling bearing is a needle roller bearing.

[0018] After the above technical solution is implemented, the beneficial effect produced is: compared with other rolling bearings, the needle roller bearing has a smaller outer diameter, a higher rotation speed and a larger load-bearing capacity.

[0019] To further improve the technical solution, a main bearing is installed on the first main journal, and the outer diameter of the main bearing is the same as the outer diameter of the needle bearing.

[0020] After implementing the above technical solution, the beneficial effect is: a plurality of bearing mounting holes are provided on the casing, and the outer diameter of the main bearing is the same as the outer diameter of the needle bearing, so that all the bearing mounting holes can be bored out with one cutter, thereby improving the consistency of the sizes of the bearing mounting holes.

[0021] To further improve the technical solution, the number of keyways of the external splines and the internal splines are both 12.

[0022] The number of spline grooves is set to 12, and 12 is the lowest common multiple of 2, 3, and 4, which can simultaneously meet the positioning needs of opposed four-cylinder, opposed six-cylinder, and opposed eight-cylinder aircraft engines regarding the misalignment angles between the extended cranks.

[0023] A crankshaft press-fitting method, for a crankshaft with an extended component, firstly performs split press-fitting: press-fitting a left crank, two connecting rods, a crank disk in the extended component, and an extended crank into a left crank-connecting rod component, and press-fitting a right crank, two connecting rods, another crank disk in the extended component, and another extended crank into a right crank-connecting rod component; then performs overall press-fitting: installing a rolling bearing on a connecting sleeve, staggering the left crank-connecting rod component and the right crank-connecting rod component by 0° or 180° through the positioning of the connecting sleeve, and then press-fitting them together;

[0024] For a crankshaft with more than two extended components, first perform separate press assembly: press the left crank, the right crank, an extended component and a connecting rod into a left crank-connecting rod assembly and a right crank-connecting rod assembly, and press the remaining extended components and connecting rods into an extended crank-connecting rod assembly; then perform overall press assembly: install a rolling bearing on the connecting sleeve, and evenly stagger the left crank-connecting rod assembly, the right crank-connecting rod assembly and the extended crank-connecting rod assembly along the circumferential direction through the positioning of the connecting sleeve, and then press them together.

[0025] After the above technical solution is implemented, compared with the background technology, the beneficial effect produced is: the crankshaft pressing method can ensure the coaxiality and misalignment angle between the cranks, and improve the yield rate of the crankshaft.

[0026] To further improve the technical solution, the left crank-connecting rod assembly, the right crank-connecting rod assembly, and the extended crank-connecting rod assembly are coaxially positioned during the overall press assembly.

[0027] After the implementation of the above technical solution, the beneficial effect produced is: the left crank-connecting rod assembly, the right crank-connecting rod assembly, and the extended crank-connecting rod assembly are coaxially positioned, which can further improve the coaxiality and misalignment angle between each crank.

[0028] To further improve the technical solution, a plurality of adjustable support blocks are placed in the suspended parts of the left crank-connecting rod assembly, the right crank-connecting rod assembly, and the extended crank-connecting rod assembly. When the whole is pressed together, the adjustable support blocks are used to prevent the left crank-connecting rod assembly, the right crank-connecting rod assembly, and the extended crank-connecting rod assembly from deformation.

[0029] After the above technical solution is implemented, the beneficial effect is that the crank is an eccentric structure, and the suspended part will be deformed when the whole is pressed. After the adjustable support block is set, the adjustable support block can support the suspended part to prevent the left crank connecting rod assembly, the right crank connecting rod assembly, and the extended crank connecting rod assembly from being deformed.

[0030] To further improve the technical solution, the adjustable support block is formed by threading bolts and tightening nuts.

[0031] After implementing the above technical solution, the beneficial effects are: the height of the suspended part is not fixed, but varies. The adjustable support block has a screw connection structure and is adjustable in height. First, it can provide gapless support for the suspended part to prevent deformation; second, after press-fitting, the adjustable support block can be easily removed by loosening the top nut. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Attached Figure 1 Shown is a structural schematic diagram of an opposed four-cylinder aircraft engine crankshaft.

[0033] Attached Figure 2 The attached Figure 1 Schematic diagram of the decomposition structure.

[0034] Attached Figure 3 Shown is another structural schematic diagram of an opposed four-cylinder aircraft engine crankshaft.

[0035] Attached Figure 4 Shown is a schematic structural diagram of an opposed six-cylinder aircraft engine crankshaft.

[0036] Attached Figure 5 Shown is a schematic structural diagram of an opposed eight-cylinder aircraft engine crankshaft.

[0037] Attached Figure 6 Shown is a schematic diagram of the structure of the split press assembly of the four-crank crankshaft.

[0038] Attached Figure 7 Shown is a schematic structural diagram of the integral press assembly of a four-crank crankshaft.

[0039] Attached Figure 8 Shown is a schematic diagram of the structure of the six-crank crankshaft split press assembly.

[0040] Attached Fig. 9 Shown is a schematic structural diagram of the integral press-fitting of a six-crank crankshaft.

[0041] In the attached drawings: 1. left crank; 11. first main journal; 12. first connecting rod journal; 2. right crank; 3. extension assembly; 31. extension crank; 311. second main journal; 312. second connecting rod journal; 32. crank plate; 33. connecting sleeve; 34. needle bearing; 35. spacer sleeve; 4. connecting rod; 5. main bearing; 6. left crank-connecting rod assembly; 7. right crank-connecting rod assembly; 8. extension crank-connecting rod assembly; 9. adjustable support block. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that in the description of the present invention, the terms "front", "rear", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal connection of two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0043] Refer to the attached Figure 1 and attached Figure 2 , attached Figure 1 The diagram shows a structural diagram of a crankshaft of an opposed four-cylinder aircraft engine. Figure 2 The attached Figure 1 Schematic diagram of the decomposition structure. Figure 1 and attached Figure 2 It can be seen that the opposed four-cylinder aircraft engine crankshaft consists of a left crank 1, a right crank 2 and an expansion assembly 3, wherein the left crank 1 and the right crank 2 have a first main journal 11 on one side and a first connecting rod journal 12 on the other side, and a connecting rod 4 is installed on the first connecting rod journal 12.

[0044] The expansion assembly 3 includes a pair of expansion cranks 31, a pair of crank plates 32, a connecting sleeve 33 and a rolling bearing. Among them, the expansion crank 31 has a second main journal 311 on one side and a second connecting rod journal 312 on the other side, and a connecting rod 4 is installed on the second connecting rod journal 312. An external spline is provided on the second main journal 311, and the keyway of the external spline has a relatively strict angle relationship with the second connecting rod journal 312 with the second main journal as the axis. In this embodiment, the number of keyways of the external spline is 12, and the angle between the keyway and the second connecting rod journal 312 is 15°.

[0045] The crank plate 32 has two pin holes, one for interference connection with the first connecting rod journal 12 , and the other for interference connection with the second connecting rod journal 312 .

[0046] The connecting sleeve 33 is arranged between a pair of expansion cranks 31. An internal spline is arranged in the connecting sleeve 33. The internal spline matches the external spline and also has 12 keyways. The function of the connecting sleeve 33 is to locate and connect the second main journals 311 on the pair of expansion cranks 31, and connect the left half and the right half of the crankshaft into a whole. The connection process can adopt a normal temperature interference press process or a low temperature cold shrink press process.

[0047] The rolling bearing is mounted on the connecting sleeve 33 to support the second main journal 311. In this embodiment, the rolling bearing is two needle roller bearings 34, which have the advantages of small outer diameter, high rotation speed and large bearing capacity. It is worth noting that the rolling bearing can also be a ball bearing or a roller bearing.

[0048] It is also worth noting that the rolling bearing is installed on the connecting sleeve 33 before the connecting sleeve 33 and the second main journal 311 are pressed together, so that the rolling bearing is installed on the crankshaft. Since the rolling bearing has the advantages of high speed, low friction, and long service life, and the wear surface is limited to the rolling element and the inner and outer ring tracks, the problem of easy wear of the second main journal 311 is fundamentally solved.

[0049] A spacer 35 is provided between the two needle roller bearings 34, and the spacer 35 separates the two rolling bearings and axially limits the two rolling bearings. The spacer 35 is provided with an oil inlet hole and an oil groove, and during operation, lubricating oil enters the rolling bearing through the oil inlet hole and the oil groove to lubricate the needle roller bearings 34.

[0050] A main bearing 5 is mounted on the first main journal 11 of the left crank 1 and the right crank 2, and the outer diameter of the main bearing 5 is the same as the outer diameter of the two needle bearings 34. Such a design facilitates the processing of the bearing mounting holes on the casing.

[0051] Refer to the attached Figure 3 , attached Figure 3Another structural schematic diagram of the crankshaft of an opposed four-cylinder aircraft engine is shown. Figure 1 and attached Figure 3 It can be seen that through the matching positioning of the inner spline and the outer spline, the attached Figure 1 The misalignment angle between the second connecting rod journal 312 of the pair of extended cranks 31 is 0°. Figure 3 A pair of extended cranks 31 in the embodiment of the present invention have a misalignment angle of 180° between their second connecting rod journals 312. Obviously, these two types of crankshafts only differ in the firing order.

[0052] Refer to the attached Figure 4 , attached Figure 4 The figure shows the structure of the crankshaft of an opposed six-cylinder aircraft engine. Figure 4 It can be seen that the six-cylinder aircraft engine crankshaft consists of a left crank 1, a right crank 2 and two expansion components 3. Through the coordination and positioning of the internal spline and the external spline, the misalignment angles of each expansion crank 31 are 0°, 120° and 240° respectively.

[0053] Refer to the attached Figure 5 , attached Figure 5 The figure shows the structure of the crankshaft of an opposed eight-cylinder aircraft engine. Figure 5 It can be seen that the eight-cylinder aircraft engine crankshaft consists of a left crank 1, a right crank 2 and three extension components 3. Through the coordination and positioning of the internal spline and the external spline, the misalignment angles of each extension crank 31 are 0°, 90°, 180° and 270° respectively.

[0054] From the above, it can be seen that by adding or removing expansion components, various types of aircraft engines can be matched, greatly reducing the processing difficulty and manufacturing cost of multi-crank crankshafts. In addition, the installation of rolling bearings on the crankshaft is realized, fundamentally solving the problem of easy wear of the second main journal.

[0055] It can also be seen that for opposed four-cylinder aircraft engines, the cranks are offset by 0° or 180°, and at least 2 spline grooves are required to achieve the positioning between the extended cranks. For opposed six-cylinder aircraft engines, the cranks are offset by 0°, 120°, and 240°, and at least 3 spline grooves are required to achieve the positioning between the extended cranks. For opposed eight-cylinder aircraft engines, the cranks are offset by 0°, 90°, 180°, and 270°, and at least 4 spline grooves are required to achieve the positioning between the extended cranks.

[0056] Since 12 is the least common multiple of 2, 3, and 4, setting the number of keyways to 12 can simultaneously meet the positioning requirements of the offset angles between the extended cranks of opposed four-cylinder, opposed six-cylinder, and opposed eight-cylinder aircraft engines. In addition, as long as the angle relationship between the external spline keyway and the second connecting rod journal 312 is strictly required in processing, the offset angles between the cranks can be guaranteed.

[0057] In order to solve the problems that the coaxiality and misalignment angles between the cranks are difficult to ensure, the qualified rate is low and the production cost is high, the present invention also provides a crank press-fitting method.

[0058] For a four-crank crankshaft with one extension assembly, the crank press assembly method uses the following steps:

[0059] 1. Split press assembly: press the left crank 1, two connecting rods 4, one crank disk 32 in the expansion assembly 3, and one expansion crank 31 into a left crank-connecting rod assembly 6; press the right crank 2, two connecting rods 4, another crank disk 32 in the expansion assembly 3, and another expansion crank 31 into a right crank-connecting rod assembly 7.

[0060] Refer to the attached Figure 6 Taking the left crank connecting rod assembly as an example, the split press-fitting die is composed of a guide column, a fixed die and two movable dies. The crank plate 32 is fixed on the fixed die, and the left crank 1 and the expansion crank 31 are installed on the movable die. The press-fitting die can ensure the coaxiality between the left crank 1, the crank plate 32 and the expansion crank 31. When the split press-fitting is performed, the hydraulic cylinder is started to push the left crank 1 and the expansion crank 31 toward each other from both sides, and the left crank 1, the crank plate 32 and the expansion crank 31 are pressed together.

[0061] 2. Integral press-fitting: Install the rolling bearing on the connecting sleeve, and through the positioning of the connecting sleeve 33, stagger the left crank connecting rod assembly 6 and the right crank connecting rod assembly 7 by 0° or 180°, and then press-fit them together.

[0062] Refer to the attached Figure 7 The integral press-fitting die is composed of a guide column, a fixed die and a movable die. The left crank connecting rod assembly 6 is installed on the movable die, and the right crank connecting rod assembly 7 is installed on the fixed die. The coaxiality of the left crank connecting rod assembly 6 and the right crank connecting rod assembly 7 is ensured by the integral press-fitting die. Before the integral press-fitting, the left crank connecting rod assembly 6 and the right crank connecting rod assembly 7 are staggered by 0° or 180° through the positioning and guidance of the internal spline on the connecting sleeve 33, and then the hydraulic cylinder is started to press the left crank connecting rod assembly 6, the right crank connecting rod assembly 7 and the connecting sleeve 33 together to complete the press-fitting of the four-crank crankshaft.

[0063] For crankshafts with more than two expansion components, take a six-crank crankshaft as an example, and use the following steps:

[0064] 1. Split press assembly: press the left crank 1, the right crank 2, an expansion component 3 and the connecting rod 4 into a left crank-connecting rod assembly 6 and a right crank-connecting rod assembly 7, and press the remaining expansion components 3 and connecting rods 4 into an expansion crank-connecting rod assembly 8.

[0065] Refer to the attached Figure 8 Taking the extended crank-connecting rod assembly as an example, the extended assembly 3 and the connecting rod 4 are press-assembled into the extended crank-connecting rod assembly 8 by a split press-assembly mold.

[0066] 2. Overall press-fitting: Install the rolling bearing on the connecting sleeve 33, and evenly stagger the left crank-connecting rod assembly 6, the right crank-connecting rod assembly 7, and the extended crank-connecting rod assembly 8 along the circumferential direction through the positioning of the connecting sleeve 33, and then press-fit them together.

[0067] Refer to the attached Fig. 9 . The overall press-fitting mold consists of a guide column, a fixed mold and two movable molds. The extended crank connecting rod assembly 8 is fixed on the fixed mold, and the left crank connecting rod assembly 6 and the right crank connecting rod assembly 7 are installed on the movable mold. Before the overall press-fitting, the left crank connecting rod assembly 6, the extended crank connecting rod assembly 8, and the right crank connecting rod assembly 7 are staggered by 0°, 120°, and 240° respectively through the positioning and guiding of the internal spline on the connecting sleeve 33, and then the hydraulic cylinder is started to press the left crank connecting rod assembly 6, the extended crank connecting rod assembly 8, the right crank connecting rod assembly 7, and the connecting sleeve 33 together to complete the press-fitting of the six-crank crankshaft. The eight-crank crankshaft and the twelve-crank crankshaft are also made in the same way.

[0068] With attached Figure 7 The difference is that before the overall press-fitting, a plurality of adjustable support blocks 9 are placed in the suspended parts of the left crank-connecting rod assembly 6, the right crank-connecting rod assembly 7, and the extended crank-connecting rod assembly 8. The adjustable support blocks 9 can support the suspended parts to prevent deformation of the left crank-connecting rod assembly 6, the right crank-connecting rod assembly 7, and the extended crank-connecting rod assembly 8. In this embodiment, the adjustable support blocks 9 are formed by bolts and tightening nuts.

[0069] The crank is an eccentric structure, and the suspended part will be deformed when the whole is pressed. In addition, the height of the suspended part is not fixed, but varies. The adjustable support block has a screw-connected structure and is adjustable in height. First, it can provide gapless support for the suspended part to prevent deformation; second, after press-fitting, the adjustable support block can be easily removed by loosening the top nut.

[0070] Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A split aircraft engine crankshaft, characterized by: It consists of a left crank, a right crank and at least one expansion component, wherein the left crank and the right crank have a first main journal and a first connecting rod journal; the expansion component includes a pair of expansion cranks, a pair of crank plates, a connecting sleeve and a rolling bearing, wherein the crank plate has two pin holes, and the expansion crank has a second main journal and a second connecting rod journal; an external spline is provided on the second main journal, with the second main journal as the axis, and the keyway of the external spline has a certain angle relationship with the second connecting rod journal; an internal spline is provided in the connecting sleeve, and the connecting sleeve is used to position and connect the second main journals on a pair of expansion cranks; the rolling bearing is installed on the connecting sleeve to support the second main journal.

2. A split aircraft engine crankshaft as claimed in claim 1, characterized in that: There are two rolling bearings, and the expansion component also includes a spacer sleeve, which is arranged between the two rolling bearings and is provided with an oil inlet hole and an oil groove.

3. A split aircraft engine crankshaft as claimed in claim 2, characterized in that: The rolling bearing is a needle roller bearing.

4. A split aircraft engine crankshaft as claimed in claim 3, characterized in that: A main bearing is mounted on the first main journal, and the outer diameter of the main bearing is the same as the outer diameter of the needle roller bearing.

5. The split aircraft engine crankshaft according to claim 1, characterized in that: The number of keyways for both external and internal splines is 12.

6. A crankshaft press-assembly method applied to a split aircraft engine crankshaft as claimed in any one of claims 1 to 5, characterized in that: For a crankshaft with an extended component, first perform split press assembly: press the left crank, two connecting rods, one crank disc in the extended component, and one extended crank into a left crank-connecting rod component, and press the right crank, two connecting rods, another crank disc in the extended component, and another extended crank into a right crank-connecting rod component; then perform overall press assembly: install a rolling bearing on the connecting sleeve, and stagger the left crank-connecting rod component and the right crank-connecting rod component by 0° or 180° through the positioning of the connecting sleeve, and then press them together; For a crankshaft with more than two extended components, first perform separate press assembly: press the left crank, the right crank, an extended component and a connecting rod into a left crank-connecting rod assembly and a right crank-connecting rod assembly, and press the remaining extended components and connecting rods into an extended crank-connecting rod assembly; then perform overall press assembly: install a rolling bearing on the connecting sleeve, and evenly stagger the left crank-connecting rod assembly, the right crank-connecting rod assembly and the extended crank-connecting rod assembly along the circumferential direction through the positioning of the connecting sleeve, and then press them together.

7. A crankshaft press-assembly method according to claim 6, characterized in that: During the overall press assembly, the left crank-connecting rod assembly, the right crank-connecting rod assembly, and the extended crank-connecting rod assembly are coaxially positioned.

8. A crankshaft press-assembly method according to claim 7, characterized in that: A plurality of adjustable support blocks are placed at the suspended parts of the left crank-connecting rod assembly, the right crank-connecting rod assembly and the extended crank-connecting rod assembly. When the whole is pressed together, the adjustable support blocks are used to prevent the left crank-connecting rod assembly, the right crank-connecting rod assembly and the extended crank-connecting rod assembly from deformation.

9. A crankshaft press-assembly method according to claim 8, characterized in that: The adjustable support block is formed by screwing bolts and nuts.

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