Internal lubrication structure in the engine transmission system

Abstract

The present invention discloses an internal lubrication structure in an engine transmission system, comprising: a casing assembly, inside which there are a first gear and a second gear, and the first gear is rotatably supported by a first bearing set, and the second gear is rotatably supported by a second bearing set. The casing assembly further includes a nozzle, an oil guiding shaft set and a plug, the oil guiding shaft set is axially installed in the shaft holes of the first gear and the second gear, and is respectively spline-connected to the shaft holes of the first gear and the second gear, and the nozzle and the plug are respectively arranged at both ends of the oil guiding shaft set. A communicating lubricating oil path is provided in the oil guiding shaft set, the first gear and the second gear, so as to enable the lubricating oil sprayed by the nozzle to enter the lubricating oil path, and under the action of the centripetal force generated by rotation, lubricate the first bearing set, the second bearing set and the two spline connection parts respectively through the lubricating oil path. The structure of the present invention can save the structural layout space, make the structural design of the engine simple and the number of parts small, and at the same time improve the lubrication efficiency and the reliability of the engine.

Description

Technical Field

[0001] The present invention relates to the field of structural design of engine transmission systems, and in particular, to an internal lubrication structure in an engine transmission system. Background Art

[0002] The rotating parts in an aeroengine have the characteristics of heavy load and high speed, and need to be fully lubricated and cooled to ensure their normal and reliable operation, which is particularly important at the meshing of gear teeth, splines, bearings and other parts.

[0003] In existing solutions, there are mainly two ways to lubricate: one is to design special lubricating nozzles at the meshing of gear teeth, splines and bearings respectively to spray lubrication on them; the other is to design a small number of nozzles in the accessory drive case, which do not directly lubricate these parts, but use the oil mist environment formed by these nozzles under high temperature and sputtering conditions to lubricate all parts without distinction.

[0004] Both of the above two lubrication methods have obvious disadvantages: the first one designs 1 special lubricating nozzle at each key part, which will make the structural design of the engine complex (the increase in oil circuit design and nozzle design), the number of parts increases, and it will also increase the demand for the oil supply capacity of the oil pump, all of which will increase the weight of the engine. At the same time, the increase in parts and oil circuits will also reduce the reliability of the engine; the second one uses the oil mist lubrication method for all parts, which is only applicable to the situation of small rotational speed and low load. The spline is generally located in the inner cavity of the gear shaft, and it is basically impossible to be lubricated and cooled in this lubrication method. Summary of the Invention

[0005] The present invention provides an internal lubrication structure in an engine transmission system to solve the technical problems existing in the existing lubrication methods, such as complex structural design of the engine, large number of parts, strong demand for the oil supply capacity of the oil pump, low reliability of the engine, and only applicable to small rotational speed and low load.

[0006] The technical solution adopted by the present invention is as follows:

[0007] An internal lubrication structure in an engine transmission system, comprising: a casing assembly, in which a first gear and a second gear are coaxially and spaced apart, and the first gear is rotatably supported by a first bearing set, and the second gear is rotatably supported by a second bearing set; a nozzle, an oil guiding shaft set and a plug are coaxially and sequentially spaced in the casing assembly, the oil guiding shaft set is axially installed in the shaft holes of the first gear and the second gear, and is respectively spline-connected with the shaft holes of the first gear and the second gear, and the nozzle and the plug are respectively arranged at both ends of the oil guiding shaft set; a lubricating oil path is provided in the oil guiding shaft set, the first gear and the second gear for enabling the lubricating oil sprayed by the nozzle to enter the lubricating oil path and lubricate the first bearing set, the second bearing set and two spline connection parts respectively under the action of the centripetal force generated by rotation.

[0008] Further, the oil guiding shaft set includes a plug and a spline shaft that are coaxially and spaced apart; the plug is inserted into the shaft hole of the first gear from the first end of the first gear and plugs the first end of the shaft hole of the first gear; both ends of the spline shaft are respectively located in the shaft holes of the first gear and the second gear, and are connected to the first gear through a first spline structure and to the second gear through a second spline structure.

[0009] Further, the first bearing set includes a first bearing and a second bearing installed at both ends of the first gear; the second bearing set includes a third bearing and a fourth bearing installed at both ends of the second gear.

[0010] Further, the lubricating oil path includes a first lubricating oil circuit, a second lubricating oil circuit and a third lubricating oil circuit that are connected; the first lubricating oil circuit includes a first central hole axially penetrating through the plug, a circumferential ring cavity formed by concave of the outer peripheral surface of the plug, a first oil passing hole opened on the plug and connecting the first central hole and the circumferential ring cavity, and a second oil passing hole opened on the first gear and connecting the circumferential ring cavity and the first bearing; the second lubricating oil circuit includes a first axial gap between the plug and the spline shaft, a first circumferential gap between the spline shaft and the shaft hole of the first gear, and a third oil passing hole opened on the first gear and connecting the first circumferential gap and the second bearing; the third lubricating oil circuit includes a second central hole axially penetrating through the spline shaft, a second axial gap between the second end of the spline shaft and the plug, a second circumferential gap between the spline shaft and the shaft hole of the second gear, and a fourth oil passing hole and a fifth oil passing hole opened on the second gear and respectively connecting the second circumferential gap and the third bearing and the fourth bearing.

[0011] Further, let the spraying aperture of the nozzle be E, the distance from the oil inlet end of the plug to the first oil passing hole be A1, the axial length of the plug be A2, the axial length of the spline shaft be A3, the aperture of the second oil passing hole be C, the aperture of the third oil passing hole be D, the aperture of the fourth oil passing hole be G, and the aperture of the fifth oil passing hole be J; then: E = 1 - 1.2 mm; A1 = E; A2 = E; A2 + A3 ≤ 200 mm; C = D = G = J = E - 0.2.

[0012] Further, let the aperture of the first central hole be F, then: F = 8 - 11 mm.

[0013] Further, a tapered hole in an inverted cone shape is machined concavely at the first end of the spline shaft near the plug. Let the large-end aperture of the tapered hole be B and the small-end aperture be A4, then: F + 2 < B ≤ F + 6; A4 ≥ 10 mm.

[0014] Further, oil passing grooves for allowing lubricating oil to pass through are respectively provided concavely on the end faces at both ends of the spline shaft. Let the groove depth of the oil passing groove be A5, then: A5 ≥ 2 mm.

[0015] Further, the internal lubrication structure of the engine transmission system further includes a first seal, a second seal and a third seal; the first seal and the second seal are respectively installed on the outer circle of the plug and are arranged on both sides of the circumferential annular cavity to prevent the lubricating oil in the circumferential annular cavity from leaking through the gap between the plug and the first gear shaft hole; an annular flange that protrudes outward and is annular is further provided on the outer circle of the second end of the spline shaft, and the third seal is installed on the outer circle of the annular flange to be cooperatively arranged with the plug cover to prevent the lubricating oil in the second annular gap from leaking through the gap between the spline shaft and the second gear shaft hole.

[0016] Further, the casing assembly includes a first casing, a connecting pipe and a second casing that are sequentially arranged along the axial direction and are connected; the nozzle and the first gear are installed in the first casing at intervals along the axial direction, and the second gear is installed in the second casing; the first end of the spline shaft is located inside the first gear, and its opposite second end passes through the connecting pipe and extends into the second gear.

[0017] The present invention has the following beneficial effects:

[0018] In the internal lubrication structure of the engine transmission system of the present invention, for parts such as bearings and splines, by designing a nozzle, lubrication of multiple splines and multiple sets of bearing groups is simultaneously achieved. Compared with the lubrication method of setting a dedicated nozzle at each position, the structural layout space can be greatly saved, the structural design of the engine is simple, the number of parts is small, thereby reducing the machining difficulty and weight of the engine, and the demand for the oil supply capacity of the oil pump. At the same time, the reduction of parts and the lubricating oil circuit will also improve the lubrication efficiency and the reliability of the engine, and it is applicable to situations with relatively high rotational speeds and high loads; compared with the lubrication method using an oil mist environment, each lubrication point can be more fully lubricated; in the internal lubrication structure of the engine transmission system of the present invention, by utilizing the characteristics of the lubricating oil forming oil slinging under the action of centrifugal force, the design of the lubricating oil circuit and the radial lubrication of the bearings are realized.

[0019] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 is a disassembled schematic diagram of the internal lubrication structure in the engine transmission system of the preferred embodiment of the present invention before assembly;

[0022] Figure 2 is a schematic diagram of the internal lubrication structure in the engine transmission system of the preferred embodiment of the present invention after assembly;

[0023] Figure 3 is Figure 1 a schematic diagram of the oil passage structure in

[0024] LEGEND DESCRIPTION

[0025] 10. Casing assembly; 11. First casing; 12. Connecting pipe; 13. Second casing; 20. First gear; 30. Second gear; 41. First bearing; 42. Second bearing; 51. Third bearing; 52. Fourth bearing; 60. Nozzle; 71. Plug; 72. Spline shaft; 720. Oil passage; 80. Plug cover; 91. First lubricating oil circuit; 911. First central hole; 912. Circumferential annular cavity; 913. First oil passage hole; 914. Second oil passage hole; 92. Second lubricating oil circuit; 921. First axial clearance; 922. First circumferential clearance; 923. Third oil passage hole; 93. Third lubricating oil circuit; 931. Second central hole; 932. Second axial clearance; 933. Second circumferential clearance; 934. Fourth oil passage hole; 935. Fifth oil passage hole; 111. First seal; 112. Second seal; 113. Third seal. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will describe in detail the embodiments of the present invention with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the following.

[0027] Refer to Figure 1 and Figure 2, a preferred embodiment of the present invention provides an internal lubrication structure for an engine transmission system, including: a casing assembly 10, in which a first gear 20 and a second gear 30 are coaxially and spaced apart, and the first gear 20 is rotatably supported by a first bearing group, and the second gear 30 is rotatably supported by a second bearing group. The casing assembly 10 further includes a nozzle 60, an oil guiding shaft group and a plug 80 that are coaxially and sequentially spaced apart. The oil guiding shaft group is axially installed in the shaft holes of the first gear 20 and the second gear 30, and is respectively spline-connected to the shaft holes of the first gear 20 and the second gear 30. The nozzle 60 and the plug 80 are respectively arranged at both ends of the oil guiding shaft group. The oil guiding shaft group, the first gear 20 and the second gear 30 are provided with a connected lubricating oil path for allowing the lubricating oil sprayed by the nozzle 60 to enter the lubricating oil path, and lubricating the first bearing group, the second bearing group and two spline connection parts respectively through the lubricating oil path under the action of the centripetal force generated by rotation.

[0028] As Figure 2 shown, the lubricating oil sprayed from the nozzle 60 will diverge when sprayed under the given oil supply temperature and oil supply pressure of the engine. Since the oil guiding shaft group, the first gear 20 and the second gear 30 are all rotating parts during operation, after the lubricating oil enters the oil guiding shaft group, under the action of centrifugal force and through the guiding action of the lubricating oil path, it will respectively enter the first bearing group, the second bearing group and two spline connection parts between the oil guiding shaft group and the first gear 20 and the second gear 30, so as to realize the lubrication of the first bearing group, the second bearing group and two spline connection parts respectively; after the lubricating oil lubricates the first bearing group and the second bearing group, it returns to the casing assembly 10 under the action of gravity and finally enters the lubricating oil pump for recirculation.

[0029] In the internal lubrication structure of the engine transmission system of the present invention, for parts such as bearings and splines, by designing a nozzle 60, the lubrication of multiple splines and multiple bearing groups can be realized simultaneously. Compared with the lubrication method of setting a dedicated nozzle at each position, the structural layout space can be greatly saved, the structural design of the engine can be simplified, the number of parts can be reduced, thereby reducing the processing difficulty and weight of the engine, as well as the demand for the oil supply capacity of the lubricating oil pump. At the same time, the reduction of parts and the lubricating oil path will also improve the lubrication efficiency and the reliability of the engine, and it is applicable to situations with relatively high rotational speeds and high loads; compared with the lubrication method using an oil mist environment, each lubrication point can be lubricated more fully; in the internal lubrication structure of the engine transmission system of the present invention, by utilizing the characteristic that the lubricating oil forms oil throwing under the action of centrifugal force, the design of the lubricating oil path and the radial lubrication of the bearings are realized.

[0030] Optionally, as Figure 2As shown, the oil guiding shaft group includes a plug 71 and a spline shaft 72 that are coaxially and spaced apart. The plug 71 is inserted into the shaft hole of the first gear 20 from the first end of the first gear 20, and seals the first end of the shaft hole of the first gear 20. Both ends of the spline shaft 72 are located in the shaft holes of the first gear 20 and the second gear 30 respectively, and are connected to the first gear 20 through a first spline structure and to the second gear 30 through a second spline structure. The structural design of the oil guiding shaft group is simple, easy to prepare and process, and has a low processing cost.

[0031] Optionally, as Figure 1 shown, the first bearing group includes a first bearing 41 and a second bearing 42 installed at both ends of the first gear 20. The first gear 20 is simply supported and easy to set. The second bearing group includes a third bearing 51 and a fourth bearing 52 installed at both ends of the second gear 30. The second gear 30 is simply supported and easy to set. Optionally, in the present invention, the first gear 20 is a cylindrical gear and the second gear 30 is a bevel gear.

[0032] Optionally, as Figure 2 shown, the lubricating oil path includes a first lubricating oil circuit 91, a second lubricating oil circuit 92, and a third lubricating oil circuit 93 that are connected. The first lubricating oil circuit 91 includes a first central hole 911 that axially penetrates the plug 71, a circumferential annular cavity 912 formed by concave inward on the outer peripheral surface of the plug 71, a first oil passing hole 913 opened on the plug 71 and communicating the first central hole 911 and the circumferential annular cavity 912, and a second oil passing hole 914 opened on the first gear 20 and communicating the circumferential annular cavity 912 and the first bearing 41. The second lubricating oil circuit 92 includes a first axial gap 921 between the plug 71 and the spline shaft 72, a first circumferential gap 922 between the spline shaft 72 and the shaft hole of the first gear 20, and a third oil passing hole 923 opened on the first gear 20 and communicating the first circumferential gap 922 and the second bearing 42. The third lubricating oil circuit 93 includes a second central hole 931 that axially penetrates the spline shaft 72, a second axial gap 932 between the second end of the spline shaft 72 and the plug cover 80, a second circumferential gap 933 between the spline shaft 72 and the shaft hole of the second gear 30, and a fourth oil passing hole 934 and a fifth oil passing hole 935 opened on the second gear 30 and respectively communicating the second circumferential gap 933 and the third bearing 51 and the fourth bearing 52.

[0033] As Figure 2As shown, the lubricating oil ejected from the nozzle 60 will diverge when ejected under the given oil supply temperature and pressure of the engine. The plug 71, spline shaft 72, first gear 20, and second gear 30 are all rotating parts during operation. Therefore, the lubricating oil entering the plug 71 will adhere to the wall surface of the first central hole 911 of the plug 71 under the action of centrifugal force. When a part of the lubricating oil passes through the first oil passage hole 913 of the plug 71, the lubricating oil will be ejected under the action of centrifugal force and enter the circumferential annular cavity 912, and then reach the first bearing 41 through the second oil passage hole 914 to lubricate it; the remaining lubricating oil moves to the right after leaving the plug 71. When it reaches the first axial clearance 921 between the plug 71 and the spline shaft 72, a part enters the first circumferential clearance 922 between the plug 71 and the spline shaft 72 to lubricate the spline engagement part of the spline shaft 72 and the first gear 20, and then lubricates the second bearing 42 through the third oil passage hole 923; another part of the lubricating oil enters the second central hole 931 inside the spline shaft, reaches the plug cover 80, and enters the second circumferential clearance 933 through the second axial clearance 932 between the plug cover 80 and the spline shaft 72 to lubricate the spline engagement part of the second gear 30 and the spline shaft 72, and then reaches the third bearing 51 through the fourth oil passage hole 934 on the second gear 30 to lubricate it, and reaches the fourth bearing 52 through the fifth oil passage hole 935 to lubricate it.

[0034] In the structure of the present invention, the lubricating oil ejected from one nozzle 60 realizes the lubrication of two splines and four bearings, greatly improving the lubrication efficiency, significantly reducing the number of lubricating oil nozzle designs and the number of lubricating oil pipelines, reducing the structural complexity and weight of the engine, and realizing the reuse of the lubricating oil. Multiple lubrications of the spline and bearings are achieved on one lubricating oil return circuit, and the spline is lubricated first and then the bearing.

[0035] Optionally, as Figure 2 shown, let the ejection aperture of the nozzle 60 be E, the distance from the oil inlet end of the plug 71 to the first oil passage hole 913 be A1, the axial length of the plug 71 be A2, the axial length of the spline shaft 72 be A3, the aperture of the second oil passage hole 914 be C, the aperture of the third oil passage hole 923 be D, the aperture of the fourth oil passage hole 934 be G, and the aperture of the fifth oil passage hole 935 be J. Then:

[0036] E = 1 - 1.2 mm.

[0037] A1 = 25 - 35E.

[0038] A2 = 55 - 65E.

[0039] A2 + A3 ≤ 200 mm.

[0040] C = D = G = J = E - 0.2.

[0041] In actual design, the axial length A2 of the plug 71 needs to be jointly designed with the structures of the first gear 20 and the spline shaft 72: at a specific working temperature and working pressure, the lubricating oil will diverge after leaving the orifice of the nozzle 60. The farther it leaves, the larger the outward expansion angle. To ensure that there is enough lubricating oil in the third lubricating oil circuit 93, the axial distance A2 of the plug 71 cannot be too long. At the same time, the large-end aperture B of the tapered hole of the spline shaft 72 cannot be too small (to be limited later). At the same time, to ensure that there is also enough oil volume in the first lubricating oil circuit 91 and the second lubricating oil circuit 92, the axial distance A2 of the plug 71 cannot be too short. Therefore, after long-term exploration and a large number of tests by the inventors of the present application, the injection aperture E of the nozzle 60, the aperture C of the second oil passage hole 914, the aperture D of the third oil passage hole 923, the aperture G of the fourth oil passage hole 934, the aperture J of the fifth oil passage hole 935, and the axial length A2 of the plug 71 are determined through computational simulation or are measured and calibrated through a lubricating oil volume test, that is, the specific limitations of the above E, A2, C, D, G, J values are obtained. Then, A1 and A3 are determined by combining these limit values with computational simulation or a lubricating oil volume test.

[0042] Optionally, as Figure 2 shown, let the aperture of the first central hole 911 be F, then: F = 8 - 11 mm. The limitation of the F value is also determined through computational simulation or is measured and calibrated through a lubricating oil volume test.

[0043] Optionally, as Figure 2 and Figure 3 shown, the first end of the spline shaft 72 near the plug 71 is recessed and processed with an inverted conical tapered hole. Let the large-end aperture of the tapered hole be B and the small-end aperture be A4, then:

[0044] F + 2 < B ≤ F + 6.

[0045] A4 ≥ 10 mm.

[0046] In actual design, B and A4 are also determined by referring to the above method through computational simulation or are measured and calibrated through a lubricating oil volume test.

[0047] Optionally, as Figure 1 and Figure 3 shown, the end faces at both ends of the spline shaft 72 are respectively provided with recessed oil passage grooves 720 for the lubricating oil to pass through. Let the groove depth of the oil passage groove 720 be A5, then:

[0048] A5 ≥ 2 mm.

[0049] In actual design, the spline shaft 72 is a floating shaft. To prevent the spline shaft 72 from being too tightly fitted with the first gear 20 or the plug cover 80 during operation, which may cause the lubricating oil to be unable to pass through, oil grooves 720 are respectively designed on the end faces at both ends of the spline shaft 72. The depth of the oil grooves 720 is also determined by calculation and simulation with reference to the above method, or determined by actual measurement and calibration through a lubricating oil quantity test.

[0050] Optionally, as Figure 2 shown, the internal lubrication structure of the engine transmission system further includes a first seal 111, a second seal 112 and a third seal 113. The first seal 111 and the second seal 112 are respectively installed on the outer circumference of the plug 71 and are located on both sides of the circumferential annular cavity 912 to prevent the lubricating oil in the circumferential annular cavity 912 from leaking through the gap between the plug 71 and the shaft hole of the first gear 20. An outwardly protruding and annular flange is also provided on the outer circumference of the second end of the spline shaft 72, and the third seal 113 is installed on the outer circumference of the flange to cooperate with the plug cover 80 to prevent the lubricating oil in the second annular gap from leaking through the gap between the spline shaft 72 and the shaft hole of the second gear 30.

[0051] Optionally, as Figure 2 shown, the casing assembly 10 includes a first casing 11, a connecting pipe 12 and a second casing 13 that are arranged and connected in sequence along the axial direction. The nozzle 60 and the first gear 20 are installed in the first casing 11 at intervals along the axial direction, and the second gear 30 is installed in the second casing 13. The first end of the spline shaft 72 is located inside the first gear 20, and its opposite second end passes through the connecting pipe 12 and extends into the second gear 30. The structure of the casing assembly 10 is simple and easy to process, and the overall layout is compact and reasonable, which can effectively save the installation space inside the engine.

[0052] The installation process of the internal lubrication structure of the engine transmission system of the present invention is as follows: First, the plug cover 80 is installed into the bevel gear to form an interference fit, and then the fourth bearing 52 is installed onto the bevel gear to form a gear assembly; then the first bearing 41 is installed into the casing cover of the first casing 11, the second bearing 42 is installed into the first casing 11, and the third bearing 51 is installed into the second casing 13; then the cylindrical gear is installed into the first casing 11, the bevel gear is installed into the second casing 13, and then the casing cover of the first casing 11 is installed with the first casing 11 through a stud; finally, the spline shaft 72, the plug 71 and the nozzle 60 are installed into the shaft holes of the cylindrical gear and the bevel gear in sequence from left to right, and the assembly process is as Figure 1 shown.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An internal lubrication structure in an engine transmission system, characterized in that, it includes: A casing assembly (10), in which a first gear (20) and a second gear (30) are coaxially and spaced apart. The first gear (20) is rotationally supported by a first bearing set, and the second gear (30) is rotationally supported by a second bearing set; A nozzle (60), an oil guiding shaft group, and a plug (80) are coaxially and sequentially spaced in the casing assembly (10). The oil guiding shaft group is axially installed in the shaft holes of the first gear (20) and the second gear (30), and is respectively spline-connected to the shaft holes of the first gear (20) and the second gear (30). The nozzle (60) and the plug (80) are respectively arranged at both ends of the oil guiding shaft group; A lubricating oil path is provided in the oil guiding shaft group, the first gear (20), and the second gear (30) for enabling the lubricating oil sprayed by the nozzle (60) to enter the lubricating oil path and lubricate the first bearing set, the second bearing set, and two spline joints respectively under the action of the centripetal force generated by rotation; The oil guiding shaft group includes a plug (71) and a spline shaft (72) that are coaxially and spaced apart; the plug (71) is inserted into the shaft hole of the first gear (20) from the first end of the first gear (20) and plugs the first end of the shaft hole of the first gear (20); both ends of the spline shaft (72) are located in the shaft holes of the first gear (20) and the second gear (30), and are connected to the first gear (20) through a first spline structure and to the second gear (30) through a second spline structure; The first bearing set includes a first bearing (41) and a second bearing (42) installed at both ends of the first gear (20); the second bearing set includes a third bearing (51) and a fourth bearing (52) installed at both ends of the second gear (30).

2. The internal lubrication structure in an engine transmission system according to claim 1, characterized in that, the lubricating oil path includes a connected first lubricating oil circuit (91), a second lubricating oil circuit (92), and a third lubricating oil circuit (93); The first lubricating oil circuit (91) includes a first central hole (911) axially penetrating the plug (71), a circumferential annular cavity (912) formed by concaving the outer peripheral surface of the plug (71), a first oil passing hole (913) opened on the plug (71) and connecting the first central hole (911) and the circumferential annular cavity (912), and a second oil passing hole (914) opened on the first gear (20) and connecting the circumferential annular cavity (912) and the first bearing (41); The second lubricating oil circuit (92) includes a first axial clearance (921) between the plug (71) and the spline shaft (72), a first circumferential clearance (922) between the spline shaft (72) and the shaft hole of the first gear (20), and a third oil passage hole (923) formed in the first gear (20) and communicating the first circumferential clearance (922) and the second bearing (42); The third lubricating oil circuit (93) includes a second central hole (931) axially penetrating the spline shaft (72), a second axial clearance (932) between the second end of the spline shaft (72) and the plug cover (80), a second circumferential clearance (933) between the spline shaft (72) and the shaft hole of the second gear (30), and a fourth oil passage hole (934) and a fifth oil passage hole (935) formed in the second gear (30) and respectively communicating the second circumferential clearance (933) with the third bearing (51) and the fourth bearing (52).

3. The internal lubrication structure of the engine transmission system according to claim 2, characterized in that, assuming that the injection aperture of the nozzle (60) is E, the distance from the oil inlet end of the plug (71) to the first oil passage hole (913) is A1, the axial length of the plug (71) is A2, the axial length of the spline shaft (72) is A3, the aperture of the second oil passage hole (914) is C, the aperture of the third oil passage hole (923) is D, the aperture of the fourth oil passage hole (934) is G, and the aperture of the fifth oil passage hole (935) is J; then: E = 1 - 1.2 mm; A1 = (25 - 35)E; A2 = (55 - 65)E; A2 + A3 ≤ 200 mm; C = D = G = J = E - 0.

2.

4. The internal lubrication structure of the engine transmission system according to claim 2, characterized in that, assuming that the aperture of the first central hole (911) is F, then: F = 8 - 11 mm.

5. The internal lubrication structure of the engine transmission system according to claim 4, characterized in that, a tapered hole in an inverted cone shape is recessed and processed at the first end of the spline shaft (72) close to the plug (71). Assuming that the large-end aperture of the tapered hole is B and the small-end aperture is A4, then: F + 2 < B ≤ F + 6; A4 ≥ 10 mm.

6. The internal lubrication structure of the engine transmission system according to claim 2, characterized in that, oil passage grooves (720) for allowing lubricating oil to pass through are respectively and recessedly provided on the end faces at both ends of the spline shaft (72). Assuming that the groove depth of the oil passage grooves (720) is A5, then: A5 ≥ 2 mm.

7. The internal lubrication structure of the engine transmission system according to claim 2, characterized in that, the internal lubrication structure of the engine transmission system further includes a first seal (111), a second seal (112) and a third seal (113); The first seal (111) and the second seal (112) are respectively installed on the outer circumference of the plug (71) and are located on both sides of the circumferential annular cavity (912) to prevent the lubricating oil in the circumferential annular cavity (912) from leaking through the gap between the plug (71) and the shaft hole of the first gear (20). An outwardly protruding and annular flange is further provided on the outer circumference of the second end of the spline shaft (72). The third seal (113) is installed on the outer circumference of the flange to cooperate with the plug cover (80) to prevent the lubricating oil in the second circumferential gap (933) from leaking through the gap between the spline shaft (72) and the shaft hole of the second gear (30).

8. The internal lubrication structure in the engine transmission system according to claim 2, characterized in that the casing assembly (10) includes a first casing (11), a connecting pipe (12) and a second casing (13) which are arranged in sequence and connected along the axial direction; the nozzle (60) and the first gear (20) are installed in the first casing (11) at intervals along the axial direction, and the second gear (30) is installed in the second casing (13); the first end of the spline shaft (72) is located inside the first gear (20), and its opposite second end passes through the connecting pipe (12) and extends into the second gear (30).

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