Two-stage gear train engine accessory driving system

Abstract

The utility model discloses a two-stage gear train engine accessory driving system which comprises a first-stage transmission unit and a second-stage transmission unit, wherein the first-stage transmission unit is composed of a crankshaft belt wheel, an automatic tensioner, a power steering pump wheel, an air pump wheel, a generator, a fan wheel and a poly V-belt, and the second-stage transmission unit is composed of a crankshaft belt wheel and an air conditioner pump wheel. The power steering pump wheel and the air conditioner pump wheel are installed on the left side and the right side of the crankshaft belt wheel respectively, the air pump wheel is arranged above the power steering pump wheel, the generator is arranged above the air conditioner pump wheel, the fan wheel is arranged above the crankshaft belt wheel, and the poly V-belt extends upwards from the crankshaft belt wheel, winds around a driving wheel of the automatic tensioner and then winds around the power steering pump wheel downwards. The air conditioner pump wheel is wound around the air pump wheel, extends upwards after winding around the water pump wheel, continues to extend to a belt wheel of the generator after winding around the air pump wheel, then rotates and extends to surround the fan wheel and finally rewinds to a crankshaft belt wheel, and the air conditioner pump wheel is in transmission connection with the crankshaft belt wheel through an elastic belt so that the air conditioner pump can be independently driven by the crankshaft belt wheel to rotate.

Description

Technical Field

[0001] The utility model relates to the technical field of engines, in particular to a two-stage gear train engine accessory drive system. Background Art

[0002] Traditional engine accessory drive systems primarily utilize a single-stage belt drive structure, which presents significant technical limitations. As engine compartment space becomes increasingly compact and accessory loads continue to increase, existing drive solutions face the following technical bottlenecks:

[0003] 1. Low space utilization: Single-stage gear trains require an idler pulley to maintain the wrap angle, resulting in excessive radial dimensions. For example, in fan drives, traditional structures require a fixed speed ratio of 1:1.4 and rely on an idler pulley to adjust the wrap angle, increasing space requirements by 15%-20%.

[0004] 2. Poor dynamic response: In long-span single-stage transmissions, belt vibration is significant. Experimental data shows that when the transmission span is greater than 800mm, the belt vibration amplitude will increase by 40%, accelerating belt fatigue fracture.

[0005] 3. Insufficient compatibility: Large-load accessories such as air-conditioning pumps are fixedly integrated and cannot be installed as needed. When the air-conditioning pump is removed, the entire gear train needs to be replaced, and the modification cost increases by 30%.

[0006] 4. Significant energy efficiency loss: Multiple idler pulleys increase friction losses. Tests show that each additional idler pulley reduces transmission efficiency by 2%-3%, leaving the accessory system efficiency at only 85%-88%.

[0007] Therefore, it is urgent to improve the existing engine accessory drive system. Utility Model Content

[0008] In order to solve the problems mentioned in the above background technology, the present invention provides a two-stage gear train engine accessory drive system.

[0009] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0010] The two-stage gear train engine accessory drive system includes a primary transmission unit consisting of a crankshaft pulley, an automatic tensioner, a power steering pump pulley, an air pump pulley, a generator, a fan pulley and a multi-V belt, and a secondary transmission unit consisting of a crankshaft pulley and an air conditioning pump pulley. The power steering pump pulley and the air conditioning pump pulley are respectively installed on the left and right sides of the crankshaft pulley, the air pump pulley is arranged above the power steering pump pulley, the generator is arranged above the air conditioning pump pulley, and the fan pulley is arranged above the crankshaft pulley. The multi-V belt extends upward from the crankshaft pulley and passes around the driving pulley of the automatic tensioner, then downwardly wraps around the power steering pump pulley, then extends upward after passing around the water pump pulley, and after being wrapped around the air pump pulley, continues to extend to the pulley of the generator, then rotates 180 degrees, extends around the fan pulley, and finally rewinds to the crankshaft pulley;

[0011] In addition to the primary pulley for the multi-V belt to wrap around, the crankshaft pulley also has a secondary pulley for the elastic belt to wrap around. The air-conditioning pump pulley is connected to the crankshaft pulley through the elastic belt so that the air-conditioning pump can be independently driven to rotate by the crankshaft pulley.

[0012] Preferably, the automatic tensioner includes a driving wheel, a fixed magazine box and a snap-fit ​​magazine box. The fixed magazine box is fixedly installed on the engine accessory magazine. The snap-fit ​​magazine box is coaxially installed with the fixed magazine box and can rotate axially freely. The driving wheel can be axially rotatably installed on the snap-fit ​​magazine box to guide and withstand the pulling force of the winding wheel of the multi-V belt.

[0013] Preferably, the bottom plate of the fixed magazine box has an arc groove, and a push plate with a track inserted into the arc groove is provided in the fixed magazine box. The push plate can move along the arc groove in the fixed magazine box. A docking tube with a track inserted into the arc groove is also provided in the fixed magazine box, and a return spring is installed between the docking tube and the push plate.

[0014] Preferably, a central adjustment rod is provided at the central axis of the fixed magazine box, a locking magazine is installed on the top plate of the snapping magazine box, the top end of the central adjustment rod is provided with an anti-slip block with a larger diameter, and the locking magazine has a chamber that allows the anti-slip block to be set therein and rotate freely, and the diameter of the channel leading downward from the chamber is smaller than the anti-slip block, so that the snapping magazine box can be stably installed with the fixed magazine box, and the snapping magazine box after installation can be linked to the movement of the docking tube due to the change in the position of the driving wheel.

[0015] Preferably, a hydraulic channel is provided in the bottom plate, the hydraulic channel is connected with the arc groove, a hydraulic plug rod inserted into the hydraulic channel is provided on the side of the push plate opposite to the return spring, a hydraulic connecting cavity for passing the anti-slip block upward is provided in the central adjusting rod, a hydraulic adjusting assembly is provided in the hydraulic connecting cavity, and the chamber in the engaging bin passes to the outside in the opposite direction of docking with the fixed bin box.

[0016] Preferably, the hydraulic adjustment assembly includes a coarse adjustment head, an extension rod and a hydraulic plug plate. The outer peripheral wall of the coarse adjustment head is provided with a coarse adjustment thread with a large gap to cooperate with the coarse adjustment thread provided on the inner wall of the hydraulic connecting cavity. The upper end of the extension rod has an anti-slip block provided in the coarse adjustment head. The hydraulic plug plate is installed at one end of the extension rod facing the bottom of the center adjustment rod. The extension rod has a hydraulic inner cavity inside, which flows to the bottom of the center adjustment rod so that the hydraulic transition plug provided on the side of the hydraulic plug plate facing the extension rod can be inserted into it.

[0017] Preferably, the end of the hydraulic cavity away from the bottom plate is connected to the fine adjustment channel set in the coarse adjustment head, the fine adjustment channel has fine threads and a fine adjustment plug set inside it, the fine adjustment plug cooperates with the fine adjustment channel thread, and the fine adjustment plug is inserted into the hydraulic cavity.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The drive system layout design provided by the present invention has an accessory wrap angle that far exceeds the minimum design requirements, greatly reducing the space occupied by the drive system. The automatic tensioner acts directly on the loose edge of the multi-V belt, reducing the number of adjustment components and the setup cost. The crankshaft directly drives the crankshaft pulley, eliminating the intermediate transmission shaft, reducing weight, and reducing the overall layout space. The multi-V belt transmission span is significantly reduced, and the dynamic response capability is improved. The elastic belt naturally shrinks to form a secondary gear train, and the deformation compensation of the elastic belt replaces the traditional idler pulley to achieve a zero idler design that effectively reduces energy efficiency losses. The air-conditioning pump wheel is connected to the crankshaft pulley through an elastic belt transmission, so that the air-conditioning pump can be independently driven to rotate by the crankshaft pulley. When the air-conditioning pump is removed, it can be disassembled separately without affecting the transmission of other components, thereby improving compatibility. The automatic tensioner can be adjusted coarsely and finely, enabling the system to reach the optimal operating state. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic structural diagram of the two-stage gear train engine accessory drive system of the present invention from one viewing angle;

[0022] Figure 2 This is a structural schematic diagram of the two-stage gear train engine accessory drive system of the present invention from another viewing angle;

[0023] Figure 3 This is a structural schematic diagram of the automatic tensioner described in the utility model;

[0024] Figure 4 This is a schematic diagram of the disassembled structure of the automatic tensioner of the present utility model;

[0025] Figure 5 This is a schematic diagram of the internal structure of the fixed storage box of the present invention;

[0026] Figure 6 This is a structural schematic diagram of the central adjustment rod and hydraulic adjustment assembly described in the present utility model.

[0027] In the figure: 1. Crankshaft pulley; 2. Automatic tensioner; 201. Arc groove; 202. Hydraulic channel; 203. Hydraulic connecting chamber; 204. Hydraulic inner chamber; 205. Fine adjustment channel; 21. Driving wheel; 22. Fixed magazine; 221. Bottom plate; 222. Push plate; 223. Docking sleeve; 224. Return spring; 225. Center adjustment rod; 226. Anti-slip block; 227. Hydraulic plug rod; 23. Snap-fit ​​magazine; 231. Insert rod; 232. Snap-fit ​​magazine; 24. Hydraulic adjustment assembly; 241. Coarse adjustment head; 242. Extension rod; 243. Hydraulic plug plate; 244. Hydraulic transition plug; 245. Fine adjustment plug; 3. Power steering pump wheel; 4. Air pump wheel; 5. Generator; 6. Fan wheel; 7. Air conditioning pump wheel; 8. Multi-V belt; 9. Elastic belt DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1

[0030] Reference Figure 1-6 The two-stage gear train engine accessory drive system includes a crankshaft pulley 1, an automatic tensioner 2, a power steering pump pulley 3, an air pump pulley 4, a generator 5, a fan pulley 6 and an air conditioning pump pulley 7. The primary transmission unit composed of the crankshaft pulley 1, the automatic tensioner 2, the power steering pump pulley 3, the air pump pulley 4, the generator 5, the fan pulley 6 and the multi-V belt 8 is driven by the multi-V belt 8, and the secondary transmission unit composed of the crankshaft pulley 1 and the air conditioning pump pulley 7 is driven by an elastic belt 9.

[0031] Specifically, the power steering pump wheel 3 and the air conditioning pump wheel 7 are respectively installed on the left and right sides of the crankshaft pulley 1, the air pump wheel 4 is arranged above the power steering pump wheel 3, the generator 5 is arranged above the air conditioning pump wheel 7, and the fan wheel 6 is arranged above the crankshaft pulley 1. The multi-V belt 8 is a closed wheel belt with a specification of 8PK2218. The multi-V belt 8 extends upward from the crankshaft pulley 1 and passes around the driving wheel 21 of the automatic tensioner 2, and then wraps around the power steering pump wheel 3 downward, extends upward after passing around the water pump wheel, and continues to extend to the pulley of the generator 5 after wrapping around the air pump wheel 4, then rotates one hundred and eighty degrees and extends around the fan wheel 6, and finally rolls back to the crankshaft pulley 1. In this way, after the crankshaft of the engine is driven to rotate, the multi-V belt 8 can be used to drive the power steering pump wheel 3, water pump, air pump wheel 4, generator 5 and fan wheel 6 around which the multi-V belt 8 passes to rotate.

[0032] The specific speed ratio and wrap angle parameters are as follows:

[0033] name Effective diameter (mm) Wrap angle (°) speed ratio crankshaft 137 214 1.0 fan wheel 132 170 1.07 dynamo 55.5 184 2.42 Air pump wheel 177 177 0.78 water pump 88 98 1.62 Power steering pump 107 210 1.27 Drive wheel 75 157 1.9

[0034] Under the drive system layout design provided by the present invention, the wrap angles of each accessory far exceed the minimum design requirements, thereby greatly reducing the space occupied by the drive system.

[0035] In addition to the primary pulley for the multi-V belt 8 to wrap around, the crankshaft pulley 1 also has a secondary pulley for the elastic belt 9 to wrap around. The air-conditioning pump pulley 7 is connected to the crankshaft pulley 1 through the elastic belt 9, so that the air-conditioning pump can be independently driven to rotate by the crankshaft pulley 1. When the air-conditioning pump is removed, it can be removed separately without affecting the transmission of other components. The elastic belt 9 is a closed wheel belt with a specification of 4PK821. The elastic belt 9 has a rope layer based on PET material to achieve 5% elastic deformation capacity. The deformation compensation of the elastic belt 9 (radial deformation of 3-5mm) replaces the traditional idler pulley, realizing a zero idler pulley design and effectively reducing energy efficiency loss.

[0036] Example 2

[0037] Reference Figure 1-6 The difference between this embodiment and embodiment 1 is that the automatic tensioner 2 includes a driving wheel 21, a fixed magazine box 22 and a snap-fit ​​magazine box 23. The fixed magazine box 22 is fixedly installed on the engine accessory magazine. The snap-fit ​​magazine box 23 is coaxially installed with the fixed magazine box 22 and can rotate axially freely. The driving wheel 21 can be axially rotatably installed on the snap-fit ​​magazine box 23 to guide and withstand the pulling force of the winding rotation of the multi-V belt 8. The driving wheel 21 can push the multi-V belt 8 in the opposite direction along with the snap-fit ​​magazine box 23 when the multi-V belt 8 tends to be straightened, so that the multi-V belt 8 can always be taut under high-speed rotation and effectively linked with various devices of the primary transmission unit.

[0038] The bottom plate 221 of the fixed magazine box 22 has an arc groove 201, and a pushing plate 222 with a track inserted into the arc groove 201 is provided in the fixed magazine box 22. The pushing plate 222 can move in the fixed magazine box 22 along the arc groove 201, and a docking tube 223 with a track inserted into the arc groove 201 is provided in the fixed magazine box 22. A return spring 224 is installed between the docking tube 223 and the pushing plate 222. The closer the docking tube 223 and the pushing plate 222 are to each other, the greater the elastic force generated by the compression of the return spring 224. The top plate of the snap-fit ​​magazine box 23 is fixedly installed with an insertion rod 231, and the insertion rod 231 can be inserted into the docking tube 223 so that the snap-fit ​​magazine box 23 can rotate axially along the arc groove 201 with the docking tube 223, thereby adjusting the position of the driving wheel 21.

[0039] A central adjustment rod 225 is provided at the central axis of the fixed magazine box 22, and a locking magazine 232 is installed on the top plate of the snap-fit ​​magazine box 23. The top of the central adjustment rod 225 is provided with an anti-slip block 226 with a larger diameter. The locking magazine 232 has a chamber that allows the anti-slip block 226 to be set therein and rotate freely, and the diameter of the downward passage of the chamber is smaller than the anti-slip block 226, so that the snap-fit ​​magazine box 23 can be stably installed with the fixed magazine box 22, and the snap-fit ​​magazine box 23 after installation can be linked to the movement of the docking tube 223 due to the change in the position of the driving wheel 21. When the pushing plate 222 remains in a fixed position, the movement of the docking tube 223 will cause the return spring 224 to be stretched or compressed, thereby generating a restoring elastic force.

[0040] A hydraulic channel 202 is provided in the base plate 221, and the hydraulic channel 202 is communicated with the arc groove 201. A hydraulic plug rod 227 is provided on the side of the pushing plate 222 opposite to the return spring 224, and the hydraulic fluid in the hydraulic channel 202 can push or attract the hydraulic plug rod 227 to move, thereby linking the pushing plate 222 to cause the engaging magazine 23 to rotate axially. The center adjusting rod 225 has a hydraulic connecting chamber 203 through which the anti-slip block 226 is passed upward. A hydraulic adjusting assembly 24 is provided in the hydraulic connecting chamber 203, and the chamber in the engaging magazine 232 is passed to the outside in the opposite direction of docking with the fixed magazine 22. In this way, the hydraulic adjusting assembly 24 provided on the center adjusting rod 225 and the anti-slip block 226 can be exposed to the outside of the automatic tensioner 2 for adjustment by the user.

[0041] The hydraulic adjustment assembly 24 includes a coarse adjustment head 241, an extension rod 242 and a hydraulic plug plate 243. The outer peripheral wall of the coarse adjustment head 241 is provided with a coarse adjustment thread with a large gap to cooperate with the coarse adjustment thread provided on the inner wall of the hydraulic connecting cavity 203. The upper end of the extension rod 242 is provided with an anti-slip block provided in the coarse adjustment head 241. The hydraulic plug plate 243 is installed at one end of the extension rod 242 facing the bottom of the center adjustment rod 225. The extension rod 242 has a hydraulic inner cavity 204 inside, and the hydraulic inner cavity 204 is passed to the bottom of the center adjustment rod 225 so that the hydraulic transition plug 244 provided on the side of the hydraulic plug plate 243 facing the extension rod 242 can be inserted therein.

[0042] The extension rod 242 installed in cooperation with the coarse adjustment head 241 through the anti-slip block 226 can move synchronously with the coarse adjustment head 241 along the hydraulic connecting chamber 203, but will not rotate axially with the coarse adjustment head 241. The coarse adjustment head 241 has a hexagonal head at the end away from the base plate 221, so that the user can twist the coarse adjustment head 241 to drive the entire hydraulic adjustment assembly 24 to move along the hydraulic connecting chamber 203, and then squeeze the hydraulic fluid from the hydraulic connecting chamber 203 into the hydraulic channel 202, or suck the hydraulic fluid out of the hydraulic channel 202, thereby linking the buckling box 23 to rotate axially. Since the coarse adjustment head 241 and the inner wall of the hydraulic connecting chamber 203 rely on the coarse adjustment thread, the user can twist the coarse adjustment head 241 to make the buckling box 23 rotate axially to a large extent, so that the driving wheel 21 can be quickly rotated to the appropriate position to tighten the multi-V belt 8.

[0043] The end of the hydraulic inner cavity 204 away from the bottom plate 221 is connected to the fine adjustment channel 205 set in the coarse adjustment head 241. The fine adjustment channel 205 has fine threads and a fine adjustment plug 245 set inside it. The fine adjustment plug 245 is threadedly matched with the fine adjustment channel 205, and the fine adjustment plug 245 is inserted into the hydraulic inner cavity 204. After the driving wheel 21 reaches the appropriate position, the user can push the hydraulic fluid toward or away from the hydraulic plug plate 243 by twisting the fine adjustment plug 245, thereby finely changing the position of the hydraulic plug plate 243, and linking the engaging magazine 23 to perform fine deflection, and precisely adjust the position of the driving wheel 21 to enable the system to reach the optimal operating state.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0045] In this utility model, unless otherwise expressly specified or limited, terms such as "disposed," "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; they may refer to mechanical connection, direct connection, or indirect connection through an intermediate medium; they may refer to internal communication between two elements or interaction between two elements. Those skilled in the art will be able to understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0046] The control method of the present invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by technicians in this field. The provision of power is also common knowledge in this field. In addition, the present invention is mainly used to protect mechanical devices, so the control method and circuit connection are no longer explained in detail in the present invention.

[0047] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A two-stage gear train engine accessory drive system, comprising a primary transmission unit consisting of a crankshaft pulley (1), an automatic tensioner (2), a power steering pump wheel (3), an air pump wheel (4), a generator (5), a fan wheel (6) and a poly-V belt, and a secondary transmission unit consisting of a crankshaft pulley (1) and an air conditioning pump wheel (7), characterized in that: The power steering pump wheel (3) and the air conditioning pump wheel (7) are respectively installed on the left and right sides of the crankshaft pulley (1); the air pump wheel (4) is arranged above the power steering pump wheel (3); the generator (5) is arranged above the air conditioning pump wheel (7); the fan wheel (6) is arranged above the crankshaft pulley (1); the multi-V belt (8) extends upward from the crankshaft pulley (1) and passes around the driving wheel (21) of the automatic tensioner (2) and then winds downwardly around the power steering pump wheel (3); extends upward after passing around the water pump wheel and continues to extend to the pulley of the generator (5) after winding around the air pump wheel (4); then rotates 180 degrees, extends around the fan wheel (6), and finally winds back to the crankshaft pulley (1); The automatic tensioner (2) comprises a driving wheel (21), a fixed compartment box (22) and a snap-fit ​​compartment box (23), wherein the fixed compartment box (22) is fixedly mounted on the engine accessory compartment, and the snap-fit ​​compartment box (23) is coaxially mounted with the fixed compartment box (22) and can freely rotate axially. The driving wheel (21) can be axially rotatably mounted on the snap-fit ​​compartment box (23) and is used to guide and withstand the pulling force of the winding wheel of the multi-V belt (8); The crankshaft pulley (1) has, in addition to a primary pulley around which the multi-V belt (8) is wound, a secondary pulley around which the elastic belt (9) is wound, and the air-conditioning pump wheel (7) is connected to the crankshaft pulley (1) through the elastic belt (9) so that the air-conditioning pump can be independently driven to rotate by the crankshaft pulley (1).

2. The two-stage gear train engine accessory drive system according to claim 1, characterized in that: The bottom plate (221) of the fixed magazine (22) has an arc groove (201), and a push plate (222) whose track is engaged with the arc groove (201) is provided in the fixed magazine (22). The push plate (222) can move along the arc groove (201) in the fixed magazine (22). A docking tube (223) whose track is engaged with the arc groove (201) is also provided in the fixed magazine (22), and a return spring (224) is installed between the docking tube (223) and the push plate (222).

3. The two-stage gear train engine accessory drive system according to claim 2, characterized in that: A central adjustment rod (225) is provided at the central axis of the fixed magazine box (22), a snap-fit ​​magazine (232) is installed on the top plate of the snap-fit ​​magazine box (23), a top end of the central adjustment rod (225) is provided with an anti-slip block (226) with a larger diameter, and a chamber is provided in the snap-fit ​​magazine (232) for allowing the anti-slip block (226) to be arranged therein and to rotate freely, and a diameter of a downward passage of the chamber is smaller than that of the anti-slip block (226), so that the snap-fit ​​magazine box (23) can be stably installed with the fixed magazine box (22), and the snap-fit ​​magazine box (23) after installation can be linked to move the docking tube (223) due to the change in the position of the driving wheel (21).

4. The two-stage gear train engine accessory drive system according to claim 3, characterized in that: A hydraulic channel (202) is provided in the bottom plate (221), the hydraulic channel (202) being connected to the circular arc groove (201), a hydraulic plug rod (227) inserted into the hydraulic channel (202) is provided on the side of the pushing plate (222) opposite to the return spring (224), the central adjustment rod (225) having a hydraulic communication cavity (203) extending upward through the anti-slip block (226), a hydraulic adjustment assembly (24) being provided in the hydraulic communication cavity (203), and the chamber in the engaging chamber (232) is connected to the outside in the opposite direction of docking with the fixed chamber box (22).

5. The two-stage gear train engine accessory drive system according to claim 4, characterized in that: The hydraulic adjustment assembly (24) includes a coarse adjustment head (241), an extension rod (242) and a hydraulic plug plate (243). The outer peripheral wall of the coarse adjustment head (241) is provided with a coarse adjustment thread to cooperate with the coarse adjustment thread provided on the inner wall of the hydraulic communication chamber (203). The upper end of the extension rod (242) is provided with an anti-slip block (226) provided in the coarse adjustment head (241). The hydraulic plug plate (243) is installed on one end of the extension rod (242) facing the bottom of the central adjustment rod (225). The extension rod (242) has a hydraulic inner cavity (204) inside. The hydraulic inner cavity (204) is connected to the bottom of the central adjustment rod (225) so that a hydraulic transition plug (244) provided on the side of the hydraulic plug plate (243) facing the extension rod (242) can be inserted into the hydraulic transition plug (244).

6. The two-stage gear train engine accessory drive system according to claim 5, characterized in that: One end of the hydraulic inner cavity (204) away from the bottom plate (221) is connected to a fine adjustment channel (205) provided in the coarse adjustment head (241), the fine adjustment channel (205) has fine threads and a fine adjustment plug (245) provided therein, the fine adjustment plug (245) is threadedly engaged with the fine adjustment channel (205), and the fine adjustment plug (245) is inserted into the hydraulic inner cavity (204).

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