Ventilation structure for a gearbox

Abstract

The utility model provides a kind of ventilation structure for gearbox, including first shell and second shell, the first shell with the second shell closure forms the internal cavity of gearbox, ventilation passage is formed between the joint surface of the first shell and the second shell, the ventilation passage includes air inlet end and air outlet end, the air inlet end with the internal cavity communication, the air outlet end is used to install ventilation component;Wherein, the path of the ventilation passage is configured as non-linear path with multiple changes of direction, for extending the flow distance of oil-gas mixture and realizing oil-gas separation by collision.This application is by setting ventilation passage at the joint surface of first shell and second shell, the path of this ventilation passage is configured as non-linear path with multiple changes of direction, to extend the flow distance of oil-gas mixture and realize oil-gas separation by collision, greatly reduce the filtration burden of ventilation component installed in air outlet end, greatly reduce the overall cost of ventilation system.

Description

Technical Field

[0001] This utility model relates to the field of new energy vehicle technology, and in particular to a ventilation structure for a gearbox. Background Technology

[0002] In the field of new energy vehicles, in order to ensure the normal operation of the vehicle's transmission and extend its service life, a ventilation structure is usually required to balance the pressure between the inside and outside environment of the transmission. This prevents the seals from being damaged and causing lubricating oil leakage when the pressure rises due to internal temperature changes. At the same time, it can also effectively prevent external dust, moisture and other pollutants from entering when the internal pressure drops, ensuring the cleanliness of the environment inside the transmission.

[0003] For hybrid vehicle transmissions, the internal operating conditions are more stringent than those of traditional gasoline or pure electric transmissions, placing higher demands on the performance of the venting structure. Therefore, hybrid vehicle transmissions typically use vent plugs with high breathability and waterproofing, such as labyrinth or diaphragm vent plugs, to replace traditional vent pipes and achieve pressure equalization. However, these high-performance vent plugs are not only expensive to manufacture, but also pose a risk of blockage when exposed to prolonged direct exposure to the oil mist generated by vigorous agitation. Tiny particles in the oil and gas can easily accumulate in the complex channels or on the diaphragm surface of the vent plug, severely impacting the reliability of the venting function. Utility Model Content

[0004] Based on this, the purpose of this utility model is to provide a ventilation structure for a transmission, which aims to solve the technical problem that existing hybrid vehicle transmissions typically use vent plugs with high breathability and waterproof performance. Such vent plugs are not only expensive to manufacture, but also pose a risk of being blocked by long-term oil mist impact, seriously affecting the ventilation function.

[0005] The purpose of this utility model is to provide a ventilation structure for a gearbox, including a first housing and a second housing. The first housing and the second housing are closed to form an internal cavity of the gearbox. A ventilation channel is formed between the mating surfaces of the first housing and the second housing. The ventilation channel includes an air inlet end and an air outlet end. The air inlet end communicates with the internal cavity, and the air outlet end is used to install a ventilation component. The ventilation channel is constructed as a non-linear path with multiple direction changes to extend the flow path of the oil-gas mixture and achieve oil-gas separation through collision.

[0006] In addition, the ventilation structure for the gearbox described above according to this utility model may also have the following additional technical features: Furthermore, the ventilation channel is arranged at an angle in the top region of the internal cavity, and the air inlet is provided at the lowest part of the ventilation channel.

[0007] Furthermore, the ventilation channel also includes a buffer separation section and a multi-stage reversing section disposed between the air inlet end and the air outlet end. The buffer separation section includes multiple series-connected receiving chambers. The inner diameter of the channel opening of each receiving chamber is 2mm-3mm, and the communication openings between two adjacent receiving chambers are staggered along the circumference of the chambers. Each of the accommodating chambers is formed by a second groove disposed on the second housing and a corresponding first groove disposed on the first housing.

[0008] Furthermore, the second housing is provided with a plurality of separation ribs arranged in an alternating manner, and the plurality of separation ribs divide the cavity of the second housing to form a plurality of interconnected second grooves; The first housing is provided with a plurality of closing ribs that correspond one-to-one with the positions of the plurality of separating ribs. The plurality of closing ribs divide the cavity of the first housing into a plurality of connected first grooves. When the second housing is closed with the first housing, the plurality of second grooves and the corresponding plurality of first grooves surround and form the plurality of serially connected receiving chambers.

[0009] Furthermore, the multi-stage commutation section includes at least two stages of commutation channel structure formed by connecting the center lines at a preset angle.

[0010] Furthermore, the multi-stage reversing section includes a first hole segment and a second hole segment disposed on the second housing. The second hole segment communicates with the buffer separation section through the first hole segment. The centerline of the first hole segment forms a first angle with the cavity wall plane direction of the buffer separation section, so that the first hole segment communicates with the buffer separation section to form a first-stage reversing channel. The centerline of the second hole segment forms a second angle with the centerline of the first hole segment, so that the second hole segment and the first hole segment are connected to form a secondary reversing channel.

[0011] Furthermore, both the first included angle and the second included angle are 30°-60°.

[0012] Furthermore, the multi-stage reversing section also includes a third hole section disposed on the first housing, the end of the third hole section being connected to the end of the second hole section through the inner hole of the hollow connector, and the center line of the third hole section coinciding with the center line of the second hole section.

[0013] Furthermore, the air outlet is disposed on the first housing, and the air outlet is a mounting hole. The center line of the mounting hole is perpendicular to the center line of the third hole segment, and the ventilation component is installed in the mounting hole.

[0014] Furthermore, the lowest part of the ventilation channel is provided with a return port that communicates with the internal cavity, and the return port is set independently from the air inlet.

[0015] Compared with the prior art, the beneficial effect of the ventilation structure for the gearbox of this utility model is that: by setting a ventilation channel at the joint surface of the first housing and the second housing, the path of the ventilation channel is constructed as a non-linear path with multiple changes of direction, thereby extending the flow path of the oil-gas mixture and achieving oil-gas separation through collision. In other words, this application integrates the ventilation structure design on the two components of the gearbox, namely the first housing and the second housing, so that the two are naturally closed after assembly to form a built-in, multi-stage reversing ventilation channel. The oil-gas mixture is first efficiently separated through the ventilation channel, which greatly reduces the filtration burden of the ventilation component installed at the outlet end. Therefore, it is not necessary to select expensive labyrinth or membrane high-performance ventilation plugs, and stable ventilation and protection functions can be achieved, which greatly reduces the overall cost of the ventilation system.

[0016] Specifically, the venting channel is equipped with a buffer separation section and a multi-stage reversing section between its inlet and outlet ends. The buffer separation section includes multiple series-connected receiving chambers, each with a narrow opening and staggered distribution along the circumference of the chamber. This allows the oil-gas mixture to change its direction of movement multiple times and collide with the chamber walls within the buffer separation section, thereby achieving the purpose of preliminary condensation and separation of the oil-gas mixture. Subsequently, the gas that has undergone preliminary separation undergoes at least two changes of flow direction within the multi-stage reversing section, further extending its path and promoting condensation, achieving secondary separation of the oil. This significantly reduces the oil-gas impact at the venting assembly, thereby lowering the risk of the venting assembly becoming clogged. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram of the ventilation structure for the gearbox of this utility model; Figure 2 This is a partial structural diagram of the first housing in the ventilation structure for the gearbox of this utility model; Figure 3 This is a partial structural diagram of the second housing in the ventilation structure for the gearbox of this utility model.

[0018] The above-mentioned figures include the following reference numerals: 10-first housing; 20-second housing; 30-ventilation assembly; 40-hollow connector; 50-ventilation channel; 501-inlet end; 502-separation rib; 503-sealing rib; 504-first hole section; 505-second hole section; 506-third hole section; 507-outlet end; 508-return port.

[0019] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this utility model. Detailed Implementation

[0020] To facilitate understanding of this utility model, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of this utility model are shown in the drawings. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this utility model will be more thorough and complete.

[0021] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] Please see Figures 1 to 3 The diagram shows a ventilation structure for a gearbox according to the present invention, including a first housing 10 and a second housing 20. The first housing 10 and the second housing 20 are closed to form an internal cavity of the gearbox, which is used to install transmission components such as gears and bearings, and to store lubricating oil. A continuous ventilation channel 50 is formed between the mating surfaces of the first housing 10 and the second housing 20 to realize the exchange of gas inside the gearbox with external gas and the separation of oil and gas. In this embodiment, the first housing 10 is the gearbox housing, and the second housing 20 is the front housing. The ventilation channel 50 is inclined at an angle of 5°-10° in the top region of the internal cavity, with the inclination direction pointing from the air inlet 501 to the air outlet 507. The air inlet 501 is located on the second housing 20, at the uppermost end of the internal cavity, and at the lowest part of the entire ventilation channel 50. This inclined design makes full use of gravity to assist the separated oil droplets to flow back towards the air inlet 501. Meanwhile, the path of the ventilation channel 50 is constructed as a non-linear path with multiple changes in direction. The core purpose of this design is to extend the flow path of the oil-gas mixture in the channel, providing sufficient time for oil-gas separation; and to force the oil-gas mixture to collide with the channel wall at the change of direction, thereby achieving efficient oil-gas separation by utilizing the inertial difference between oil droplets and gas, and avoiding the direct discharge of oil mist with the gas.

[0024] Furthermore, a return port 508 communicating with the internal cavity is provided at the lowest part of the ventilation passage 50. The return port 508 and the intake end 501 adopt an independent channel design so that after the gearbox cools down, due to the pressure difference, the oil that condenses and adheres to the side wall of the ventilation circuit is drawn back into the internal cavity of the gearbox through the return port 508 or the intake end 501, which avoids the oil from accumulating in the ventilation passage 50 and reduces oil loss.

[0025] Specifically, the ventilation channel 50 includes an inlet end 501 and an outlet end 507. The inlet end 501 is directly connected to the internal cavity of the gearbox to facilitate the entry of the oil-air mixture into the ventilation channel 50. The outlet end 507 is used to install the ventilation component 30. In this embodiment, the outlet end 507 is disposed on the first housing 10 and is a mounting hole. The center line of the mounting hole is perpendicular to the center line of the third hole segment 506, and the ventilation component 30 is installed in the mounting hole. The ventilation component 30 can be a waterproof vent plug, a one-way vent valve, or other structures. More specifically, in this embodiment, the mounting hole of the outlet end 507 adopts a vertical design, and its center line is perpendicular to the center line of the third hole segment 506. This vertical layout not only facilitates the installation and removal of the ventilation component 30 but also reduces the probability of external dust, rainwater, and other impurities entering the channel under gravity.

[0026] In this embodiment, the ventilation channel 50 further includes a buffer separation section and a multi-stage reversing section disposed between the air inlet end 501 and the air outlet end 507. The buffer separation section includes multiple series-connected receiving chambers, each with a volume of 5mL-10mL. The specific volume can be adjusted according to the displacement of the gearbox. Each chamber is formed by a second groove disposed on the second housing 20 and a corresponding first groove disposed on the first housing 10. When the second housing 20 and the first housing 10 are closed, the second groove and the first groove are completely aligned to form a sealed chamber structure, ensuring that the oil-gas mixture can only flow along the series direction of the chambers and cannot leak.

[0027] More specifically, the interconnecting channels of each containment chamber employ a small-diameter and staggered arrangement. In this embodiment, the inner diameter of the channel opening is only 2mm-3mm, and the connecting openings between adjacent containment chambers are not directly opposite each other, but are staggered along the circumference of the chamber. For example, if the channel opening of the preceding containment chamber is located on the left side wall of that chamber, then the channel opening of the following containment chamber is located on the corresponding right side wall. The purpose of this design is twofold: firstly, the small-diameter channel openings further slow down the flow velocity of the oil-gas mixture, allowing it more sufficient residence time in each containment chamber and ensuring that oil droplets have enough opportunity to adhere to the chamber wall; secondly, the staggered arrangement of the channel openings forces the oil-gas mixture to change direction by more than 90° when entering the next containment chamber. During this process, oil droplets will collide secondary with the edge of the channel opening and the chamber wall of the subsequent chamber due to inertia, significantly improving the initial separation effect.

[0028] Furthermore, to achieve the series connection and separation of the accommodating chambers, as well as the precise forming of the small-diameter staggered channel openings, the mating surface of the second housing 20 is provided with a plurality of staggered separating ribs 502. The height of the separating ribs 502 is flush with the mating surface of the second housing 20, and the plurality of separating ribs 502 are staggered vertically to divide the cavity of the second housing 20 into a plurality of interconnected second grooves. Correspondingly, the mating surface of the first housing 10 is provided with a plurality of closing ribs 503 corresponding one-to-one with the positions of the plurality of separating ribs 502. The height of the closing ribs 503 is flush with the mating surface of the first housing 10, and the plurality of closing ribs 503 divide the cavity of the first housing 10 into a plurality of interconnected first grooves. When the second shell 20 is closed with the first shell 10, the separating rib 502 and the closing rib 503 fit together, so that the multiple second grooves and the corresponding multiple first grooves are precisely enclosed to form multiple series of receiving chambers. This structural design not only ensures the sealing of the chambers, but also enhances the structural strength of the joint surface of the two shells through the supporting effect of the separating rib 502 and the closing rib 503.

[0029] Furthermore, the multi-stage reversing section includes at least two stages of reversing channel structures formed by the centerlines connecting at a preset angle. The inner diameter of the channel is 8mm-12mm, which can be designed according to the displacement of the transmission. In this embodiment, the multi-stage reversing section includes a first section 504 and a second section 505 disposed on the second housing 20. One end of the second section 505 is connected to the last receiving chamber of the buffer separation section through the first section 504, and the other end extends to the edge of the second housing 20. The centerline of the first section 504 forms a first angle with the plane of the cavity wall of the buffer separation section. The purpose of this angle is to cause a sudden change in the flow direction of the oil-gas mixture when it enters the first section 504 from the buffer separation section, thereby achieving oil droplet separation by inertia. The centerline of the second section 505 forms a second angle with the centerline of the first section 504, further forcing the oil-gas mixture to change its flow direction, and separating the oil droplets again by inertia.

[0030] Furthermore, both the first included angle and the second included angle are between 30° and 60°. As a specific example, in this embodiment, both the first included angle and the second included angle are 45°.

[0031] Furthermore, to achieve communication between the multi-stage reversing section and the air outlet 507, the multi-stage reversing section also includes a third hole section 506 disposed inside the first housing 10. The inner diameter of the third hole section 506 is the same as the inner diameter of the second hole section 505. One end of the third hole section 506 extends to the air outlet 507 of the first housing 10, and the other end is connected to the end of the second hole section 505 through the inner hole of the hollow connector 40. In this embodiment, the hollow connector 40 is a hollow pin, and its two ends are respectively press-fitted with the end of the second hole section 505 and the end of the third hole section 506. In practical applications, oil-resistant sealant can be applied to the fit gap between the hollow pin and the two housings to ensure that there is no leakage of oil-gas mixture at the joint surface between the second housing 20 and the first housing 10, and completely eliminate the problem of oil mist overflow caused by the failure of the connector seal. Furthermore, the centerline of the third hole section 506 is completely aligned with the centerline of the second hole section 505, and the centerline of the hollow pin is also coaxial with both. This coaxial design can prevent the oil-gas mixture from flowing turbulently when passing through the hollow pin, ensuring that the gas flows smoothly to the mounting hole of the outlet end 507.

[0032] In practical applications, the working principle of the transmission ventilation structure of this application can be as follows: When the transmission is in operation, the gears, bearings, and other components located in its internal cavity will generate severe friction during high-speed operation. This not only raises the internal temperature of the transmission but also causes the lubricating oil (usually gear oil) to atomize under high temperature and stirring, forming an oil-gas mixture. As the oil-gas mixture continues to be generated, the air pressure in the internal cavity gradually increases. At this time, the oil-gas mixture in the internal cavity will flow towards the air inlet 501 located at the lowest part of the ventilation channel 50 under the action of the air pressure difference, and then enter the interior of the ventilation channel 50.

[0033] Next, the oil-gas mixture enters a buffer separation section consisting of multiple series-connected chambers. Since each chamber is connected by small-diameter and staggered channels, the flow velocity of the oil-gas mixture undergoes two decelerations: initial deceleration within the chamber and further deceleration upon passing through the small-diameter channels, thus achieving sufficient buffering and deceleration. Simultaneously, as the oil-gas mixture passes through the staggered channels, its flow direction is forcibly changed, for example, from flowing along the bottom of the chamber to flowing along its sidewall. During this process, some larger oil droplets (≥5μm in diameter) cannot follow the gas's direction due to inertia and collide with the channel edges and chamber walls, losing kinetic energy and adhering to the chamber walls. Upon entering the next chamber, the sudden expansion of the chamber space reduces the flow velocity again, and the remaining large-diameter oil droplets continue to collide and separate with the chamber walls, completing the first efficient oil-gas separation. Meanwhile, since the ventilation channel 50 is inclined and located at the top of the internal cavity of the gearbox, the oil droplets attached to the cavity wall will gradually converge into an oil flow under the action of gravity. Finally, the oil flows back into the internal cavity of the gearbox through the return port 508 or the intake end 501 located at the lowest part of the ventilation channel 50, thereby realizing the recycling and reuse of lubricating oil and reducing the loss of lubricating oil. After initial separation in the buffer separation section (at this point, oil droplet diameter is mostly ≤5μm, and the content has been significantly reduced), the oil-gas mixture continues to flow into the multi-stage reversing section. It first enters the first orifice section 504. Because the centerline of the first orifice section 504 forms a 45° angle with the cavity wall plane of the buffer separation section, the flow direction of the oil-gas mixture suddenly changes by 45°. During this reversal, some unseparated oil droplets (3-5μm in diameter) cannot follow the gas reversal in time due to inertia and collide with the orifice wall of the first orifice section 504, adhering to the orifice wall, thus achieving a second oil-gas separation. Subsequently, the oil-gas mixture enters the second orifice section 505, which is connected to the first orifice section 504. Because the centerline of the second orifice section 505 also forms a 45° angle with the centerline of the first orifice section 504, the flow direction of the oil-gas mixture changes by 45° again. Oil droplets with a diameter of 1-3μm collide with the orifice wall of the second orifice section 505 due to inertia, completing a third oil-gas separation. After two turning collisions, most of the oil droplets in the oil-gas mixture are separated (the remaining oil droplets are mostly ≤1μm in diameter). These separated oil droplets will flow back to the buffer separation section along the hole wall (the hole wall can be treated with oleophilic treatment to facilitate the aggregation of oil droplets), and then flow back to the internal cavity through the return port 508. Finally, the gas (mainly air and a small amount of fine oil mist) after being separated by multiple reversing stages enters the third section 506 of the first housing 10 through the inner hole of the hollow pin (the coaxial design and sealing structure of the hollow pin, the second section 505, and the third section 506 ensures that the gas flows smoothly without leakage and without significant pressure loss), and then flows to the mounting hole of the outlet end 507. The venting component 30 (such as a waterproof vent plug) installed in the mounting hole further filters the fine oil mist (particle size ≤1μm) in the gas and discharges clean gas to the outside of the gearbox; at the same time, the venting component 30 has a one-way sealing function, which can prevent external dust, rainwater, impurities, etc. from entering the inside of the gearbox, thereby achieving dynamic balance of air pressure inside the gearbox and ensuring the normal operation of the gearbox.

[0034] In summary, the beneficial effects of the ventilation structure for the gearbox of this utility model are as follows: by setting a ventilation channel at the joint surface of the first housing and the second housing, the path of the ventilation channel is constructed as a non-linear path with multiple changes of direction, thereby extending the flow path of the oil-gas mixture and achieving oil-gas separation through collision. In other words, this application integrates the ventilation structure design on the two components of the gearbox, namely the first housing and the second housing, so that after the two are assembled, they naturally close to form a built-in, multi-stage reversing ventilation channel. The oil-gas mixture is first efficiently separated through the ventilation channel, which greatly reduces the filtration burden of the ventilation component installed at the outlet end. Therefore, it is not necessary to select expensive labyrinth or diaphragm high-performance ventilation plugs, and stable ventilation and protection functions can be achieved, which greatly reduces the overall cost of the ventilation system. Specifically, the venting channel is equipped with a buffer separation section and a multi-stage reversing section between its inlet and outlet ends. The buffer separation section includes multiple series-connected receiving chambers, each with a narrow opening and staggered distribution along the circumference of the chamber. This allows the oil-gas mixture to change its direction of movement multiple times and collide with the chamber walls within the buffer separation section, thereby achieving the purpose of preliminary condensation and separation of the oil-gas mixture. Subsequently, the gas that has undergone preliminary separation undergoes at least two changes of flow direction within the multi-stage reversing section, further extending its path and promoting condensation, achieving secondary separation of the oil. This significantly reduces the oil-gas impact at the venting assembly, thereby lowering the risk of the venting assembly becoming clogged.

[0035] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this utility model application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model application should be determined by the appended claims.

Claims

1. A venting structure for a gearbox, comprising a first housing and a second housing, wherein the first housing and the second housing are closed to form an internal cavity of the gearbox, characterized in that, A ventilation channel is formed between the mating surfaces of the first housing and the second housing. The ventilation channel includes an air inlet and an air outlet. The air inlet communicates with the internal cavity, and the air outlet is used to install a ventilation assembly. The ventilation channel is constructed as a non-linear path with multiple direction changes to extend the flow path of the oil-gas mixture and achieve oil-gas separation through collision.

2. The ventilation structure for a gearbox according to claim 1, characterized in that, The ventilation channel is arranged at an angle in the top area of ​​the internal cavity, and the air inlet is provided at the lowest part of the ventilation channel.

3. The ventilation structure for a gearbox according to claim 1, characterized in that, The ventilation channel also includes a buffer separation section and a multi-stage reversing section disposed between the air inlet end and the air outlet end. The buffer separation section includes multiple series-connected receiving chambers. The inner diameter of the channel opening of each receiving chamber is 2mm-3mm, and the connecting openings between two adjacent receiving chambers are staggered along the circumference of the chambers. Each of the accommodating chambers is formed by a second groove disposed on the second housing and a corresponding first groove disposed on the first housing.

4. The ventilation structure for a gearbox according to claim 3, characterized in that, The second housing is provided with a plurality of separation ribs arranged in an alternating manner, and the plurality of separation ribs divide the cavity of the second housing into a plurality of interconnected second grooves; The first housing is provided with a plurality of closing ribs that correspond one-to-one with the positions of the plurality of separating ribs. The plurality of closing ribs divide the cavity of the first housing into a plurality of connected first grooves. When the second housing is closed with the first housing, the plurality of second grooves and the corresponding plurality of first grooves surround and form the plurality of serially connected receiving chambers.

5. The ventilation structure for a gearbox according to claim 3, characterized in that, The multi-stage commutation section includes at least two stages of commutation channel structure formed by the center lines being connected at a preset angle.

6. The ventilation structure for a gearbox according to claim 5, characterized in that, The multi-stage reversing section includes a first hole section and a second hole section disposed on the second housing. The second hole section communicates with the buffer separation section through the first hole section. The centerline of the first hole section forms a first angle with the cavity wall plane direction of the buffer separation section, so that the first hole section communicates with the buffer separation section to form a first-stage reversing channel. The centerline of the second hole segment forms a second angle with the centerline of the first hole segment, so that the second hole segment and the first hole segment are connected to form a secondary reversing channel.

7. The ventilation structure for a gearbox according to claim 6, characterized in that, Both the first included angle and the second included angle are 30°-60°.

8. The ventilation structure for a gearbox according to claim 6, characterized in that, The multi-stage reversing section further includes a third hole section disposed on the first housing. The end of the third hole section is connected to the end of the second hole section through the inner hole of the hollow connector. The center line of the third hole section coincides with the center line of the second hole section.

9. The ventilation structure for a gearbox according to claim 8, characterized in that, The air outlet is disposed on the first housing and is a mounting hole. The center line of the mounting hole is perpendicular to the center line of the third hole segment, and the ventilation component is installed in the mounting hole.

10. The ventilation structure for a gearbox according to claim 2, characterized in that, The lowest part of the ventilation channel is also provided with a return port that communicates with the internal cavity, and the return port is set independently from the air inlet.

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