Speed change, clutch and vortex expander integrated structure

Abstract

The invention discloses a speed change, clutch and vortex expansion machine integrated structure which comprises a speed change structure, a clutch structure and a vortex expansion machine structure. The vortex expansion machine structure is located at the bottom of the integrated structure, and the vortex expansion machine structure is used for connecting a working medium, doing work through the connected working medium and outputting power; the clutch structure is located in the middle of the integrated structure and is in transmission fit with the vortex expansion machine structure. And the speed change structure is located at the top of the integrated structure and used for outputting low-rotating-speed high torque or high-rotating-speed low torque, and the speed change structure controls power output of the vortex expansion machine structure through the clutch structure. According to the characteristics of the expansion process in the organic Rankine cycle, a corresponding small vortex expansion structure is designed, and a compact electromagnetic clutch and two-gear speed change structure is further designed. According to the integrated structure, the expansion machine, the clutch and the speed change structure are simplified and integrated, and miniaturization of equipment and economical efficiency improvement of the equipment are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of energy and power technology, and in particular to an integrated structure of a variable speed, clutch and scroll expander. Background Art

[0002] Organic Rankine cycle (ORC) is a technology that effectively expands the application of low-temperature energy. Its principle is to use a low-boiling point organic working fluid to absorb low-temperature heat energy in the evaporator to produce organic working fluid steam with a certain temperature and pressure, which is used to drive the expander to rotate and do work. The exhaust gas of the expander after work is completed enters the condenser for condensation, and is then transported back to the evaporator by the working fluid pump to complete the cycle. This cycle can realize the conversion of thermal energy into mechanical energy. For example, by connecting the expander to a generator, it can further realize the conversion of mechanical energy into electrical energy. In recent years, with the increasing prominence of energy shortages, global warming and other problems, ORC-related technologies have received more and more attention. Compared with other low-temperature heat source utilization technologies, the ORC system can better match heat sources of different temperatures by replacing the working fluid, achieve relatively small applications, and realize distributed energy supply.

[0003] In the application scenarios of small-scale organic Rankine cycle power generation systems, isolated grid operation accounts for a large proportion. For example, the scenario of using waste heat from a ship to generate electricity for use by other equipment on the ship. However, the current small-scale ORC power generation device does not consider the load change problem during ORC isolated grid operation, resulting in the inability to maximize the power generation efficiency. Adding a variable speed structure is a common technical means to deal with the problem of load changes, but the current small-scale ORC power generation system does not have a similar structure and usage method.

[0004] There are three difficulties in adding a speed change structure to a small ORC power generation system. First, the volume of a small ORC power generation unit must be controlled within a certain range, which requires the integrated transmission structure to be compact. Second, small ORC power generation units are often expensive, and adding a transmission structure will further reduce the economic efficiency of the ORC power generation unit, so the new transmission structure is required to be simple. Finally, a clutch must be added to achieve coupling between the transmission structure and the expander to ensure system stability during speed change.

[0005] At present, the common clutch transmission structure is mostly designed for fuel vehicles or electric vehicles, which is difficult to match the scroll expander, cannot meet the needs of miniaturization, and is often high in manufacturing cost, making it difficult to directly apply it to small ORC power generation devices. Furthermore, since there is no speed change device for small ORC power generation devices, there is no corresponding speed change control method. Summary of the invention

[0006] The purpose of the present invention is to provide an integrated structure of a variable speed, clutch and scroll expander applied to a small organic Rankine cycle, so as to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides a variable speed, clutch, scroll expander integrated structure, including:

[0008] A vortex expander structure is located at the bottom of the integrated structure, and the vortex expander structure is used to connect a working medium, use the connected working medium to do work and output power;

[0009] A clutch structure, located in the middle of the integrated structure, the clutch structure and the scroll expander structure are in transmission cooperation;

[0010] The speed change structure is located at the top of the integrated structure. The speed change structure is used to output low speed and high torque or high speed and low torque. The speed change structure controls the power output of the scroll expander structure through the clutch structure.

[0011] Preferably, the scroll expander structure includes an expander casing, and a fixed scroll plate, a movable scroll plate, a movable plate bearing, a bracket body, a bracket body bearing and a crankshaft are arranged on the inner side of the expander casing; the top of the crankshaft is mounted on the expander casing through the bracket body, the crankshaft is rotatably connected to the bracket body through the bracket body bearing, and the clutch structure is transmission-coordinated with the crankshaft; the movable scroll plate is mounted on the bottom of the crankshaft through the movable plate bearing, the fixed scroll plate is fixedly mounted on the bottom of the expander casing, the fixed scroll plate and the movable scroll plate are a pair of scroll body structures with a phase angle difference of 180°; a working fluid inlet is arranged at the bottom of the expander casing, a working fluid outlet is arranged on the side wall of the expander casing, and the movable scroll plate is arranged between the working fluid inlet and the working fluid outlet.

[0012] Preferably, a circular groove is provided at the top center of the movable scroll plate, and the movable plate bearing is embedded in the circular groove.

[0013] Preferably, a plurality of spherical anti-self-rotation mechanisms are installed on the top of the movable scroll, and the movable scroll is limitedly matched with the bracket body through the spherical anti-self-rotation mechanisms.

[0014] Preferably, the clutch structure comprises a clutch housing, the bracket body is installed between the clutch housing and the expander housing by bolts; a driving shaft, a driving tube bearing, a magnetic coil, a driving plate, a driven plate, a spring, a driven bearing, a connecting sleeve and a driven shaft are arranged inside the clutch housing; the bottom end of the driving shaft is connected to the crankshaft, and the driving shaft is rotatably connected to the clutch housing through the driving tube bearing; an annular groove is provided at the top of the clutch housing, the magnetic coil is embedded in the annular groove, the driving plate is fixedly connected to the top of the driving shaft, and the magnetic coil is located below the driving plate; the connecting sleeve is slidably sleeved on the driven shaft, the connecting sleeve is rotatably connected to the clutch housing through the driven bearing, the driven plate is fixedly connected to the bottom end of the driven shaft, and the two ends of the spring are respectively fixedly connected to the driven plate and the connecting sleeve; the driven plate is located above the driving plate, and the driven plate is arranged opposite to the driving plate, and a gap is arranged between the driven plate and the driving plate; the speed change structure is in transmission cooperation with the driven shaft.

[0015] Preferably, the driven plate and the active plate are both friction plates.

[0016] Preferably, an insulating protective layer is provided in the annular groove, and the insulating protective layer is used to maintain the position stability of the magnetic coil.

[0017] Preferably, the speed change structure comprises a speed change housing, which is mounted on the top of the clutch housing by bolts; a low-speed gear set, a high-speed gear set, an output shaft and a shift fork are arranged inside the speed change housing; the output shaft is rotatably connected to the speed change housing, and the top end of the driven shaft extends into the inner side of the speed change housing and is rotatably connected to the speed change housing; the pinion of the low-speed gear set and the large gear of the high-speed gear set are both fixedly sleeved on the driven shaft, and the large gear of the low-speed gear set and the pinion of the high-speed gear set are both sleeved on the output shaft; the shift fork is sleeved on the output shaft, and the shift fork is located between the large gear of the low-speed gear set and the pinion of the high-speed gear set, an opening is opened on the speed change housing, and the end of the shift fork extends out of the speed change housing through the opening; the large gear of the low-speed gear set and the pinion of the high-speed gear set are both adjusted to a transmission connection state with the output shaft by the shift fork.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] 1. The variable speed, clutch, and scroll expander integrated structure provided by the present invention realizes the variable speed and variable torque output of the scroll expander shaft work, which is more suitable for the utilization of organic Rankine waste heat in scenarios with large load changes; it can improve the waste heat efficiency of the organic Rankine cycle system when the load changes, and enhance the economy.

[0020] 2. The present invention is an integrated vertical design, which can realize miniaturization and micro-application, and is suitable for organic Rankine waste heat utilization scenarios with restrictions on space size and weight; and because the present invention is a vertical arrangement structure from top to bottom, it is convenient for the overall organic Rankine waste heat utilization system to reduce the floor space.

[0021] 3. The clutch structure and the speed change structure in the present invention have been simplified and have a simple structure; the production cost of the entire equipment (i.e., the scroll expander, the speed change, and the clutch) can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative work.

[0023] Figure 1 It is a structural schematic diagram of the integrated structure of the variable speed, clutch and scroll expander of the present invention;

[0024] In the figure: 1.1, expander housing; 1.2, fixed scroll; 1.3, movable scroll; 1.4, spherical anti-self-rotation mechanism; 1.5, movable disk bearing; 1.6, bracket body; 1.7, bracket body bearing; 1.8, crankshaft; 1.9, working fluid inlet; 1.10, working fluid outlet; 2.1, driving shaft; 2.2, clutch housing; 2.3, driving tube bearing; 2.4, magnetic coil; 2.5, insulating protective layer; 2.6, driving plate; 2.7, driven plate; 2.8, spring; 2.9, driven bearing; 2.10, connecting sleeve; 2.11, driven shaft; 3.1, low-speed gear set; 3.2, high-speed gear set; 3.3, output shaft; 3.4, shift fork; 3.5, speed change housing. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0026] like Figure 1 As shown, the present invention provides a variable speed, clutch, scroll expander integrated structure, including:

[0027] The scroll expander structure is located at the bottom of the integrated structure. The scroll expander structure is used to connect the working fluid, use the connected working fluid to do work and output power;

[0028] The clutch structure is located in the middle of the integrated structure, and the clutch structure is coordinated with the scroll expander structure;

[0029] The speed-changing structure is located at the top of the integrated structure. The speed-changing structure is used to output low-speed high torque or high-speed low torque. The speed-changing structure controls the power output of the scroll expander structure through the clutch structure.

[0030] When the present invention is working, a working fluid containing a certain temperature and pressure enters the scroll expander structure to expand and do work, so that the scroll expander structure outputs shaft 3.3 work outwardly, and the output shaft 3.3 work is connected to the clutch structure, and the clutch structure is used to control the connection with the speed change structure, so that the power is transmitted from the scroll expander structure to the clutch structure, and then transmitted to the speed change structure output, and the speed change structure output is selected as low speed high torque or high speed low torque according to needs. The present invention realizes the variable speed and variable torque output of the scroll expander shaft work, which is more suitable for the organic Rankine waste heat utilization scenario with large load changes; it can improve the waste heat efficiency of the organic Rankine cycle system when the load changes, and enhance the economy.

[0031] Further optimization scheme, the scroll expander structure includes an expander housing 1.1, and the inner side of the expander housing 1.1 is provided with a fixed scroll plate 1.2, a movable scroll plate 1.3, a movable plate bearing 1.5, a bracket body 1.6, a bracket body bearing 1.7 and a crankshaft 1.8; the top of the crankshaft 1.8 is installed on the expander housing 1.1 through the bracket body 1.6, the crankshaft 1.8 is rotatably connected with the bracket body 1.6 through the bracket body bearing 1.7, and the clutch structure is in transmission cooperation with the crankshaft 1.8; the movable scroll The rotating disk 1.3 is installed at the bottom of the crankshaft 1.8 through the movable disk bearing 1.5, and the fixed scroll disk 1.2 is fixedly installed at the bottom of the expander casing 1.1. The fixed scroll disk 1.2 and the movable scroll disk 1.3 are a pair of vortex body structures with a phase angle difference of 180°; a working fluid inlet 1.9 is provided at the bottom of the expander casing 1.1, and a working fluid outlet 1.10 is provided on the side wall of the expander casing 1.1, and the movable scroll disk 1.3 is provided between the working fluid inlet 1.9 and the working fluid outlet 1.10.

[0032] According to a further optimization scheme, a circular groove is provided at the top center of the movable scroll plate 1.3, and the movable plate bearing 1.5 is embedded in the circular groove.

[0033] According to a further optimization scheme, a plurality of spherical anti-self-rotation mechanisms 1.4 are installed on the top of the movable scroll 1.3, and the movable scroll 1.3 is limitedly matched with the bracket body 1.6 through the spherical anti-self-rotation mechanisms 1.4.

[0034] Further optimization scheme, the clutch structure includes a clutch housing 2.2, and the bracket body 1.6 is installed between the clutch housing 2.2 and the expander housing 1.1 by bolts; the clutch housing 2.2 is provided with a driving shaft 2.1, a driving tube bearing 2.3, a magnetic coil 2.4, a driving plate 2.6, a driven plate 2.7, a spring 2.8, a driven bearing 2.9, a connecting sleeve 2.10 and a driven shaft 2.11; the bottom end of the driving shaft 2.1 is connected to the crankshaft 1.8, and the driving shaft 2.1 is rotatably connected to the clutch housing 2.2 through the driving tube bearing 2.3; an annular groove is opened on the top of the clutch housing 2.2, and the magnetic coil 2.4 is embedded in the annular groove Inside, the active plate 2.6 is fixedly connected to the top of the active shaft 2.1, and the magnetic coil 2.4 is located below the active plate 2.6; the connecting sleeve 2.10 is slidably sleeved on the driven shaft 2.11, and the connecting sleeve 2.10 is rotatably connected to the clutch housing 2.2 through the driven bearing 2.9, and the driven plate 2.7 is fixedly connected to the bottom end of the driven shaft 2.11, and the two ends of the spring 2.8 are respectively fixedly connected to the driven plate 2.7 and the connecting sleeve 2.10; the driven plate 2.7 is located above the active plate 2.6, and the driven plate 2.7 and the active plate 2.6 are arranged opposite to each other, and a gap is arranged between the driven plate 2.7 and the active plate 2.6; the speed change structure is in transmission cooperation with the driven shaft 2.11.

[0035] According to a further optimization scheme, both the driven plate 2.7 and the active plate 2.6 are friction plates.

[0036] According to a further optimization scheme, an insulating protective layer 2.5 is provided in the annular groove, and the insulating protective layer 2.5 is used to maintain the position stability of the magnetic coil 2.4.

[0037] Further optimization scheme, the speed change structure includes a speed change housing 3.5, which is installed on the top of the clutch housing 2.2 by bolts; the interior of the speed change housing 3.5 is provided with a low speed gear set 3.1, a high speed gear set 3.2, an output shaft 3.3 and a shift fork 3.4; the output shaft 3.3 is rotatably connected to the speed change housing 3.5, the top end of the driven shaft 2.11 extends into the inner side of the speed change housing 3.5, and is rotatably connected to the speed change housing 3.5; the small gear of the low speed gear set 3.1 and the large gear of the high speed gear set 3.2 are both fixedly sleeved on the driven shaft 2.1 1, the large gear of the low speed gear set 3.1 and the small gear of the high speed gear set 3.2 are both sleeved on the output shaft 3.3; the shift fork 3.4 is sleeved on the output shaft 3.3, and the shift fork 3.4 is located between the large gear of the low speed gear set 3.1 and the small gear of the high speed gear set 3.2, and an opening is opened on the speed change housing 3.5, and the end of the shift fork 3.4 extends out of the speed change housing 3.5 through the opening; the large gear of the low speed gear set 3.1 and the small gear of the high speed gear set 3.2 are both adjusted to a transmission connection state with the output shaft 3.3 through the shift fork 3.4.

[0038] The present invention provides an integrated structure of variable speed, clutch and scroll expander. When the scroll expander structure is working, a working fluid containing a certain temperature and pressure enters from the working fluid inlet 1.9 of the expander, expands and performs work in the fixed scroll 1.2 and the movable scroll 1.3, and becomes exhausted gas and flows out from the working fluid outlet 1.10. The expansion work will drive the movable scroll 1.3 to perform circular motion. The center of the top of the movable scroll 1.3 has a circular groove, in which a movable disk bearing 1.5 is embedded, and the expander crankshaft 1.8 can be installed. When the movable scroll 1.3 performs circular motion, it will drive the crankshaft 1.8 of the expander to rotate and output shaft 3.3 work outward. Three spherical anti-self-rotation mechanisms 1.4 are installed around the top of the movable scroll 1.3, which can ensure that the movable scroll 1.3 performs planar circular motion instead of rotating around the crankshaft 1.8 of the expander. The support body 1.6 and the support body bearing 1.7 provide support for the expander crankshaft 1.8 and ensure its rotation.

[0039] The clutch structure is a normally open structure, and its clutch working principle is as follows: the magnetic coil 2.4 and the insulating protective layer 2.5 are installed on the edge of the clutch housing 2.2. The active plate 2.6 and the driven plate 2.7 are a pair of friction plates with a certain space reserved. The active plate 2.6 is installed on the top of the active shaft 2.1 and will rotate with the active shaft 2.1. The driven plate 2.7 is installed on the driven shaft 2.11, with a certain up and down sliding space, and is fixed to the connecting sleeve 2.10 by the spring 2.8. The connecting sleeve 2.10 is fixed on the clutch housing 2.2 by the driven bearing 2.9, and it is guaranteed to rotate freely. When the magnetic coil 2.4 is not energized, the spring 2.8 is tightened to ensure that the driven plate 2.7 and the active plate 2.6 cannot contact. When the magnetic coil 2.4 is energized, it will generate a great suction force, attracting the driven plate 2.7 to overcome the elastic force of the spring 2.8 and slide down to contact the active plate 2.6. At this time, the rotation of the active plate 2.6 will drive the driven plate 2.7 and the spring 2.8 connected thereto and the connecting sleeve 2.10 to rotate together. The insulation protection can ensure that the magnetic coil 2.4 will not deviate due to vibration during operation.

[0040] The input shaft of the speed change structure and the clutch driven shaft 2.11 are integrated. During operation, the low-speed gear set 3.1 and the high-speed gear set 3.2 can be adjusted according to the shift fork 3.4. When speed change is required, the clutch magnetic coil 2.4 is disconnected from the power supply, and the shift fork 3.4 is used to select the output of low speed and high torque or high speed and low torque. After determining the output gear set to be used, the clutch magnetic coil 2.4 is energized, so that the power is transmitted from the scroll expander structure to the clutch structure, and then transmitted to the speed change structure for output through the output shaft 3.3.

[0041] The present invention designs a corresponding small vortex expansion structure based on the characteristics of the expansion process in the organic Rankine cycle, and further designs a compact electromagnetic clutch and two-speed transmission structure. This integrated structure simplifies and integrates the expander, clutch and transmission structure, which helps to achieve miniaturization of the equipment and improve the economy of the equipment.

[0042] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A variable speed, clutch, scroll expander integrated structure, characterized in that: include: A vortex expander structure is located at the bottom of the integrated structure, and the vortex expander structure is used to connect a working medium, use the connected working medium to do work and output power; A clutch structure, located in the middle of the integrated structure, the clutch structure and the scroll expander structure are in transmission cooperation; The speed change structure is located at the top of the integrated structure. The speed change structure is used to output low speed and high torque or high speed and low torque. The speed change structure controls the power output of the scroll expander structure through the clutch structure.

2. The integrated structure of variable speed, clutch and scroll expander according to claim 1, characterized in that: The scroll expander structure comprises an expander housing (1.1), wherein a fixed scroll (1.2), a movable scroll (1.3), a movable disk bearing (1.5), a bracket body (1.6), a bracket body bearing (1.7) and a crankshaft (1.8) are arranged on the inner side of the expander housing (1.1); the top of the crankshaft (1.8) is mounted on the expander housing (1.1) through the bracket body (1.6); the crankshaft (1.8) is rotationally connected to the bracket body (1.6) through the bracket body bearing (1.7); the clutch structure is transmission-coordinated with the crankshaft (1.8); the movable scroll (1.3) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable disk bearing (1.7); the movable scroll (1.3) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable disk bearing (1.5); the movable scroll (1.6) is rotationally coupled to the movable scroll ... 1.3) is installed at the bottom of the crankshaft (1.8) through the movable disk bearing (1.5), the fixed scroll (1.2) is fixedly installed at the bottom of the expander housing (1.1), and the fixed scroll (1.2) and the movable scroll (1.3) are a pair of vortex structures with a phase angle difference of 180°; a working fluid inlet (1.9) is provided at the bottom of the expander housing (1.1), a working fluid outlet (1.10) is provided on the side wall of the expander housing (1.1), and the movable scroll (1.3) is provided between the working fluid inlet (1.9) and the working fluid outlet (1.10).

3. The integrated structure of variable speed, clutch and scroll expander according to claim 2, characterized in that: A circular groove is provided at the top center of the movable scroll plate (1.3), and the movable plate bearing (1.5) is embedded in the circular groove.

4. The integrated structure of variable speed, clutch and scroll expander according to claim 2, characterized in that: A plurality of spherical anti-self-rotation mechanisms (1.4) are installed on the top of the movable scroll (1.3), and the movable scroll (1.3) is limitedly matched with the bracket body (1.6) through the spherical anti-self-rotation mechanisms (1.4).

5. The integrated structure of variable speed, clutch and scroll expander according to claim 2, characterized in that: The clutch structure comprises a clutch housing (2.2); the bracket body (1.6) is installed between the clutch housing (2.2) and the expander housing (1.1) by means of bolts; a driving shaft (2.1), a driving tube bearing (2.3), a magnetic coil (2.4), a driving plate (2.6), a driven plate (2.7), a spring (2.8), a driven bearing (2.9), a connecting sleeve (2.10) and a driven shaft (2.11) are arranged inside the clutch housing (2.2); the bottom end of the driving shaft (2.1) is connected to the crankshaft (1.8), and the driving shaft (2.1) is rotatably connected to the clutch housing (2.2) through the driving tube bearing (2.3); an annular groove is provided at the top of the clutch housing (2.2), the magnetic coil (2.4) is embedded in the annular groove, and the driving plate (2.6) is fixed The connecting sleeve (2.10) is slidably mounted on the driven shaft (2.11), the connecting sleeve (2.10) is rotationally connected to the clutch housing (2.2) via the driven bearing (2.9), the driven plate (2.7) is fixedly connected to the bottom end of the driven shaft (2.11), and the two ends of the spring (2.8) are respectively fixedly connected to the driven plate (2.7) and the connecting sleeve (2.10); the driven plate (2.7) is located above the driving plate (2.6), and the driven plate (2.7) and the driving plate (2.6) are arranged opposite to each other, and a gap is arranged between the driven plate (2.7) and the driving plate (2.6); the speed change structure is in transmission cooperation with the driven shaft (2.11).

6. The integrated structure of variable speed, clutch and scroll expander according to claim 5, characterized in that: The driven plate (2.7) and the active plate (2.6) are both friction plates.

7. The speed-changing, clutching, scroll expander integrated structure according to claim 5, characterized in that: An insulating protective layer (2.5) is provided in the annular groove, and the insulating protective layer (2.5) is used to maintain the position stability of the magnetic coil (2.4).

8. The speed-changing, clutching, scroll expander integrated structure according to claim 5, characterized in that: The speed change structure comprises a speed change housing (3.5), which is mounted on the top of the clutch housing (2.2) by means of bolts; a low-speed gear set (3.1), a high-speed gear set (3.2), an output shaft (3.3) and a shift fork (3.4) are arranged inside the speed change housing (3.5); the output shaft (3.3) is rotationally connected to the speed change housing (3.5); the top end of the driven shaft (2.11) extends into the inner side of the speed change housing (3.5) and is rotationally connected to the speed change housing (3.5); the pinion of the low-speed gear set (3.1) and the large gear of the high-speed gear set (3.2) are both fixedly sleeved on the driven shaft (2.11); the low-speed gear set (3.1) and the large gear of the high-speed gear set (3.2) are both fixedly sleeved on the driven shaft (2.11); The large gear of the low-speed gear set (3.1) and the small gear of the high-speed gear set (3.2) are both sleeved on the output shaft (3.3); the shift fork (3.4) is sleeved on the output shaft (3.3), and the shift fork (3.4) is located between the large gear of the low-speed gear set (3.1) and the small gear of the high-speed gear set (3.2); an opening is provided on the speed change housing (3.5), and the end of the shift fork (3.4) protrudes out of the speed change housing (3.5) through the opening; the large gear of the low-speed gear set (3.1) and the small gear of the high-speed gear set (3.2) are both adjusted to a transmission connection state with the output shaft (3.3) through the shift fork (3.4).

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