Planetary reduction gear and electric vehicle

Abstract

The application discloses a planetary reducer, which comprises a power input device, a planetary gear mechanism, a one-way locking mechanism and a single motor frame. The planetary gear mechanism comprises an outer gear ring, a plurality of planetary gears, a planet carrier and a sun gear. The outer gear ring is in transmission connection with the power input device. The planet carrier is coaxially and fixedly connected with an output shaft. The sun gear is rotatably arranged on the inner side of the planet carrier and is in meshing connection with each planetary gear. The one-way locking mechanism is in transmission cooperation with the sun gear and is used for limiting the one-way rotation of the sun gear. The axial end surface of the sun gear and the axial end surface of the corresponding position of the planet carrier are matched to form an annular oil gap. The annular oil gap is filled with transmission oil. The single motor frame can omit the double-motor cooperative control system and two sets of driving hardware, and greatly reduces the electric control difficulty and the system manufacturing cost.

Description

Technical Field

[0001] This invention relates to the field of speed reducer technology, and more particularly to a planetary speed reducer and an electric vehicle. Background Technology

[0002] Planetary gear reducers are widely used in power transmission systems of electric vehicles, industrial automation equipment, and other fields due to their large transmission ratio, compact structure, and high load-bearing capacity. However, most conventional planetary gear reducers have a fixed speed ratio, which makes it difficult to simultaneously meet the high torque requirements of heavy-load uphill driving and the high efficiency requirements of flat road driving: if the speed ratio is too large, the speed will be too high and the transmission loss will be large when driving on flat roads; if the speed ratio is too small, the torque will be insufficient when driving uphill under heavy load.

[0003] To address the aforementioned issues, existing technologies have developed two-speed planetary gearboxes, most of which achieve speed ratio switching through actuators such as electromagnetic clutches, shift forks, and spring return mechanisms. This approach suffers from the following drawbacks: First, it involves numerous electronic and mechanical actuators, resulting in a complex structure, high manufacturing costs, and the electronic control components are prone to failure under vibration and extreme temperatures, leading to insufficient reliability. Second, the shifting process involves shocks, resulting in poor transmission smoothness. Third, it requires supporting control circuits and sensors, resulting in a large overall size that is difficult to fit into the compact installation space of small vehicles such as electric tricycles. Furthermore, existing technologies also employ planetary gearboxes controlled by dual motors, where two motors drive different planetary components to achieve speed ratio switching and torque coupling. While this approach can achieve multi-speed shifting and wide-condition torque adjustment, it requires two independent motor drive and control systems, resulting in a complex overall structure, large axial and radial volume, and high manufacturing costs. Simultaneously, the speed synchronization and torque distribution of the dual motors require complex electronic control algorithms, making control difficult and placing high demands on the reliability of the controller hardware and software, hindering its large-scale application in small electric vehicles. Other purely mechanical automatic transmission solutions employ structures such as centrifugal blocks, ratchet wheels, and pawls, which still suffer from problems such as numerous parts, rapid wear, and low shift threshold accuracy. Furthermore, they cannot simultaneously address the issue of eliminating drag resistance during downhill coasting. Therefore, there is an urgent need for a single-motor planetary reducer solution that is structurally simple, requires no complex electrical control, is highly reliable, and can automatically switch speed ratios. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies, such as high control difficulty and complex overall structure.

[0005] In a first aspect, the present invention provides a planetary reducer, comprising: a power input device; a planetary gear mechanism including an external gear ring, a plurality of planet gears, a planet carrier, and a sun gear; the external gear ring is drivenly connected to the power input device, an output shaft is coaxially fixedly connected to the planet carrier, and the sun gear is rotatably coaxially disposed inside the planet carrier and meshes with each planet gear; a one-way locking mechanism, the one-way locking mechanism being drivenly engaged with the sun gear to restrict only the one-way rotation of the sun gear; an annular oil gap is formed between the axial end face of the sun gear and the corresponding axial end face of the planet carrier, and the annular oil gap is filled with transmission oil.

[0006] Optionally, the power input device includes a motor, a motor wheel, and a transition gear. The motor wheel is coaxially fixed to the output end of the motor, the motor wheel meshes with the transition gear, and the transition gear meshes with the external teeth of the external gear ring.

[0007] Optionally, the one-way locking mechanism includes a one-way bearing and a fixed shaft; a limiting groove is provided on the inner wall of the housing, the outer ring of the one-way bearing is circumferentially fixed in the limiting groove, one end of the fixed shaft is coaxially fixed to the inner ring of the one-way bearing, and the other end is coaxially fixed to the sun gear.

[0008] Optionally, the one-way bearing is a one-way needle roller bearing or a one-way wedge bearing; the fixed shaft and the sun gear are separate structures, and the fixed shaft and the sun gear are coaxially fixedly assembled by interference fit.

[0009] Optionally, one side of the axial end face of the sun gear is provided with an annular groove, and the other side of the axial end face is a plane; the corresponding mating end face of the planet carrier is provided with an annular boss adapted to the annular groove; an axial gap is left between the two axial end faces of the sun gear and the mating end faces of the planet carrier and filled with transmission oil to form the annular oil gap; the annular boss extends into the annular groove, and a mating gap is left between the annular boss and the inner wall of the annular groove, and the mating gap is connected to the axial gap on that side.

[0010] Optionally, the planetary carrier includes a first planetary end cap, a second planetary end cap, and an inner support; the outer gear ring is fixedly disposed on the periphery of the first planetary end cap and the second planetary end cap; the planetary gears are rotatably mounted on the inner support, and the inner support is coaxially fixedly connected to the output shaft; the annular boss is disposed on the inner end face of the first planetary end cap, the side of the sun gear with the annular groove is arranged facing the first planetary end cap, and the flat side of the sun gear is arranged facing the end face of the inner support.

[0011] Optionally, the axial end face clearance between the sun gear and the planet carrier is 0.1~0.5mm.

[0012] Optionally, a support bearing is installed between the output shaft and the housing; the planetary gears are rotatably mounted on the planet carrier via planetary pins, and each planetary gear is distributed at equal intervals along the circumferential direction.

[0013] Optionally, the housing includes a first housing end cover and a second housing end cover. The first housing end cover and the second housing end cover are joined together to form a sealed transmission receiving cavity. The planetary gear mechanism and the one-way locking mechanism are housed in the transmission receiving cavity, and the output shaft extends out of the first housing end cover.

[0014] In a second aspect, the present invention provides an electric vehicle including the planetary reducer described in the first aspect.

[0015] The beneficial effects of this invention are as follows: the single-motor architecture eliminates the need for a dual-motor collaborative control system and two sets of drive hardware, significantly reducing the difficulty of electrical control and the system manufacturing cost; the one-way locking mechanism can achieve one-way locking and forward following of the sun gear solely through mechanical characteristics, without the need for electrical control signal triggering, resulting in fast locking response and high reliability; the annular oil gap, combined with the fluid drag effect of the transmission oil, can automatically drive the sun gear to switch states according to load changes, eliminating the need for additional shifting actuators such as electromagnetic clutches and shift forks, resulting in a minimal overall structure with fewer parts and fewer potential failure points; the planetary reducer can automatically switch between a 1:1.8 reduction and torque-increasing mode and a 1:1 direct drive mode, which can meet the high torque requirements of heavy-load conditions while reducing gear meshing losses in light-load conditions, balancing power and transmission efficiency. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 These are assembly diagrams of the planetary gear reducer in some embodiments; Figure 2 These are cross-sectional views of the planetary gear reducer in some embodiments; Figure 3 These are exploded views of the planetary gear reducer in some embodiments; Figure 4 These are cross-sectional views of the planetary gear structure in some embodiments; Figure 5 yes Figure 4 Enlarged view of section A in the middle; Figure 6 These are exploded views of the planetary gear structure in some embodiments.

[0018] Explanation of reference numerals in the attached drawings: 1. Housing; 101. Transition gear; 102. Limiting and fixing groove; 103. First housing end cover; 104. Second housing end cover; 2. Motor; 201. Motor wheel; 3. Planetary gear mechanism; 301. External gear ring; 302. Planetary gear; 303. Planetary carrier; 304. Sun gear; 305. Annular groove; 306. Annular boss; 307. First planetary end cap; 308. Second planetary end cap; 309. Inner support; 310. Output shaft; 311. Support bearing; 4. One-way locking mechanism; 401. Annular oil gap; 402. One-way bearing; 403. Fixed shaft. Detailed Implementation

[0019] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0020] This invention provides a planetary reducer, comprising: a power input device; a planetary gear mechanism 3, including an external gear ring 301, a plurality of planet gears 302, a planet carrier 303, and a sun gear 304; the external gear ring 301 is drivenly connected to the power input device, an output shaft 310 is coaxially fixedly connected to the planet carrier 303, and the sun gear 304 is rotatably coaxially disposed inside the planet carrier 303 and meshes with each planet gear 302; a one-way locking mechanism 4, which is drivenly engaged with the sun gear 304 to restrict only the one-way rotation of the sun gear 304; an annular oil gap 401 is formed between the axial end face of the sun gear 304 and the corresponding axial end face of the planet carrier 303, and the annular oil gap 401 is filled with transmission oil.

[0021] The planetary gear mechanism 3, consisting of an external gear ring 301, several planetary gears 302, a planet carrier 303, and a sun gear 304, is the core actuator for achieving speed reduction and transmission. The external gear ring 301 serves as the power input end, receiving external power. The planetary gears 302 mesh to transmit power and achieve revolution and rotation. The planet carrier 303 serves as the power output end, converging the revolution of the planetary gears 302 and outputting torque. The sun gear 304, as a movable component, changes its position through either locking or following states. The transmission ratio of the planetary mechanism; the one-way locking mechanism 4 is in transmission cooperation with the sun gear 304. Its core function is to restrict the one-way rotation of the sun gear 304 relative to the housing 1. It is the core locking element for realizing automatic speed ratio switching; the annular oil gap 401 and the transmission oil are filled between the mating end faces of the sun gear 304 and the planetary carrier 303. When the transmission oil rotates synchronously with the planetary carrier 303, it generates fluid shear force and surface tension, forming a drag torque acting on the sun gear 304. It is the power source for driving the sun gear 304 to follow in the positive direction.

[0022] During implementation, when the device is under heavy load (such as a vehicle climbing a hill with a heavy load or starting with a full load), the load resistance is transmitted back to the planetary carrier 303 through the output shaft 310, so that the speed of the planetary carrier 303 is lower than the input speed of the power input device. The external gear ring 301 rotates forward in the direction of the input power, driving the planetary gear 302 to revolve synchronously in the forward direction through internal meshing. Simultaneously, the planetary gear 302 rotates in the forward direction. The forward rotation of the planetary gear 302 acts on the sun gear 304 through external meshing, applying a reverse driving force to the sun gear 304 in the opposite direction to the input, causing the sun gear 304 to naturally tend to rotate in the opposite direction. Forward rotation is clockwise, and reverse rotation is counterclockwise. At this time, the one-way bearing 402 is triggered and locked, restricting the reverse rotation of the sun gear 304, keeping the sun gear 304 stationary relative to the housing 1. The planetary gear mechanism 3 enters the standard reduction mode of "external gear ring 301 driving, sun gear 304 fixed, planetary carrier 303 output." In this mode, the basic reduction ratio of the mechanism is 1:1.8, meaning that for every 1.8 revolutions of the external gear ring 301, the planetary carrier 303 drives the output shaft 310 to rotate 1 revolution. The ring gear 302 achieves a speed reduction and torque amplification effect by superimposing the revolution and rotation of the planetary gear 302, thus meeting the power requirements of heavy load conditions. Under this condition, the transmission oil in the annular oil gap 401 generates a fluid drag torque as the external gear ring 301 and planetary carrier 303 rotate. However, this torque is less than the reverse torque applied to the sun gear 304 by the load through the planetary gear 302. Therefore, the sun gear 304 remains locked, and the mechanism operates stably in the deceleration gear. When the device is under light load conditions (such as a vehicle traveling at a constant speed on a flat road or running unloaded), the load resistance is greatly reduced, and the operating speed of the external gear ring 301 and planetary carrier 303 increases. The transmission oil in the housing 1 flows synchronously at high speed with the planetary carrier 303 and external gear ring 301, generating fluid shear force and surface tension in the annular oil gap 401 on both sides of the sun gear 304, forming a drag torque acting on the sun gear 304 in the positive input direction. As the rotational speed increases, the forward dragging torque gradually increases. When the forward dragging torque exceeds the reverse driving force applied by the planetary gear 302 to the sun gear 304, the reverse rotation tendency of the sun gear 304 is canceled out, and it begins to rotate in the forward direction of the input. The higher the forward rotational speed of the sun gear 304, the smaller the relative rotational speed difference between the sun gear 304, the external gear ring 301, and the planetary carrier 303, and the rotational speed of the planetary gear 302 decreases synchronously. When the forward rotational speed of the sun gear 304 driven by the hydraulic dragging torque is exactly equal to the forward rotational speed of the planetary carrier 303, there is no longer any relative rotation among the sun gear 304, planetary gear 302, external gear ring 301, and planetary carrier 303, and the rotation of the planetary gear 302 completely stops. The inner and outer rings of the one-way bearing 402 rotate synchronously in the forward direction, and the locking state is automatically released.At this time, the entire planetary gear mechanism 3 rotates synchronously as a rigid whole, with a transmission ratio of 1:1, entering a constant speed direct drive state. In this state, the planetary gear 302 has no self-rotation meshing loss, only revolution motion, and the overall transmission efficiency is significantly improved. Since the power to pull the sun gear 304 to rotate comes from the transmission oil that rotates synchronously with the planetary carrier 303, the maximum speed of the oil is the same as the speed of the planetary carrier 303. Therefore, the limit speed of the sun gear 304 is equal to the speed of the planetary carrier 303, and there will be no overspeed reverse drive. The entire speed ratio switching process is smooth and without impact. When the vehicle is coasting downhill, the wheels drive the planetary carrier 303 to rotate at high speed through the output shaft 310. At this time, the speed of the planetary carrier 303 is higher than the input speed of the external gear ring 301. The transmission force direction of the planetary gear 302 is reversed, while the sun gear 304 is still subjected to a positive force. The one-way bearing 402 remains unlocked, and the rotation at the output end will not drag the motor 2 in the reverse to generate braking resistance, which can reduce the vehicle's coasting resistance and improve the driving range. The single-motor 2 architecture eliminates the need for a dual-motor 2 collaborative control system and two sets of drive hardware, significantly reducing the difficulty of electrical control and the system manufacturing cost. The one-way locking mechanism 4 can achieve one-way locking and forward following of the sun gear 304 solely through mechanical characteristics, without the need for electrical control signal triggering, resulting in fast locking response and high reliability. The annular oil gap 401, in conjunction with the fluid drag effect of the transmission oil, can automatically drive the sun gear 304 to switch states according to load changes, eliminating the need for additional shifting actuators such as electromagnetic clutches and shift forks. The overall structure is extremely simple, with fewer parts and fewer potential failure points. This planetary reducer can automatically switch between a 1:1.8 reduction and torque-increasing mode and a 1:1 direct drive mode, which can meet the high torque requirements of heavy-load conditions while reducing gear meshing losses in light-load conditions, balancing power and transmission efficiency.

[0023] In some embodiments, the power input device includes a motor 2, a motor 2 wheel, and a transition gear 101. The motor 2 wheel is coaxially fixed to the output end of the motor 2, and the transition gear 101 is rotatably mounted in the housing 1. The motor 2 wheel meshes with the transition gear 101, and the transition gear 101 meshes with the external teeth of the external gear ring 301.

[0024] Among them, motor 2 serves as the sole power source for the entire machine, providing input speed and torque for the entire transmission system. The single-motor 2 architecture eliminates the need for multi-motor 2 collaborative control. The motor 2 wheel is coaxially fixed to the output end of motor 2 and rotates synchronously with the output shaft 310 of motor 2. Its function is to directly extract the rotational power output by motor 2 as the driving wheel of the input transmission stage. The transition gear 101 is rotatably installed inside the housing 1 and meshes between the motor 2 wheel and the outer gear ring 301. Its function is to receive the power of the motor 2 wheel and, after adjusting the speed and torque through the tooth ratio, transmit it to the outer gear ring 301 of the planetary gear mechanism 3.

[0025] During implementation, after motor 2 is powered on, the output shaft 310 drives the motor 2 wheels to rotate synchronously. The motor 2 wheels drive the transition gear 101 to rotate through gear tooth meshing, completing the first stage of reduction transmission. The transition gear 101 then drives the external gear ring 301 to rotate through gear tooth meshing, inputting power into the planetary gear mechanism 3. By matching the gear ratio between the motor 2 wheels and the transition gear 101, the input speed can be pre-adjusted so that the input speed of the external gear ring 301 matches the basic reduction ratio of the planetary gear mechanism 31:1.8, and the final output total reduction ratio meets the torque and speed requirements of the target working condition. In this scheme, the motor 2 wheels can be directly fixed to the output shaft 310 of motor 2, resulting in a short transmission path, high transmission efficiency, and convenient assembly and positioning. The transition gear 101 can play a role in speed matching and center distance compensation between the motor 2 wheels and the external gear ring 301, allowing for flexible adjustment of the input stage transmission ratio, reducing the speed ratio design pressure of the planetary gear mechanism 3. The gear meshing transmission has the characteristics of precise transmission ratio, strong load-bearing capacity, and smooth operation, ensuring the stability and reliability of power transmission.

[0026] In some cases, the single transition gear 101 can be replaced with a coaxial double gear to further increase the input stage reduction ratio without increasing the axial dimension, thereby compressing the radial volume of the whole machine. If the requirements for transmission noise are low, synchronous belt pulley transmission can be used instead of gear transmission to reduce the requirements for machining accuracy and operating noise. The number and arrangement of the transition gears 101 can be adjusted according to the installation space requirements to adapt to different internal layouts of the housing 1.

[0027] In some embodiments, the housing 1 is further included, and the one-way locking mechanism 4 includes a one-way bearing 402 and a fixed shaft 403; a limiting fixing groove 102 is provided on the inner wall of the housing 1, the outer ring of the one-way bearing 402 is circumferentially fixed in the limiting fixing groove 102, one end of the fixed shaft 403 is coaxially fixed to the inner ring of the one-way bearing 402, and the other end is coaxially fixed to the sun gear 304.

[0028] The housing 1 serves to support and protect all internal transmission components, providing an installation reference and a sealed working environment for each rotating part. A limiting and fixing groove 102 is formed on the inner wall of the housing 1 to circumferentially and axially limit the outer ring of the one-way bearing 402, ensuring that the outer ring is relatively fixed to the housing 1, providing a fixed reference for one-way locking. The outer ring of the one-way bearing 402 is fixed within the limiting and fixing groove 102, while the inner ring can rotate freely in one direction relative to the outer ring. Its core function is to achieve the mechanical function of one-way locking, only restricting the reverse rotation of the inner ring relative to the outer ring. One end of the fixed shaft 403 is fixedly connected to the inner ring of the one-way bearing 402, and the other end is coaxially fixedly connected to the sun gear 304. Its function is to connect the one-way bearing 402 and the sun gear 304, synchronously transmitting the rotation of the sun gear 304 to the inner ring of the one-way bearing 402, while ensuring the coaxiality of the rotation of the sun gear 304. During implementation, when the sun gear 304 is subjected to a reverse force, the reverse torque is transmitted to the inner ring of the one-way bearing 402 through the fixed shaft 403, causing the inner ring to rotate in the opposite direction relative to the outer ring. At this time, the internal locking structure of the one-way bearing 402 is triggered, locking the inner and outer rings together. The reverse rotation of the sun gear 304 is restricted by the housing 1, maintaining a relatively stationary state, and the planetary gear mechanism 3 enters a 1:1.8 reduction and torque increase mode. When the sun gear 304 is subjected to a positive drag torque, the positive torque is transmitted to the inner ring of the one-way bearing 402 through the fixed shaft 403, allowing the inner ring to rotate freely in the positive direction relative to the outer ring. The one-way bearing 402 does not produce a locking effect. The sun gear 304 can rotate synchronously with the planetary carrier 303, and the mechanism enters the direct drive mode. In this solution, the limiting and fixing groove 102 can provide precise installation positioning for the one-way bearing 402, ensuring the coaxiality of the bearing and the sun gear 304, avoiding abnormal wear caused by off-center load. The one-way bearing 402 can achieve one-way locking function purely mechanically, without external power and electrical control signals. The locking response speed is fast and the operation reliability is high. The fixed shaft 403 can prevent the sun gear 304 from directly mating with the inner ring of the one-way bearing 402, reducing the machining accuracy requirements of the sun gear 304, while dispersing the locking impact force and improving the structural strength and service life of the sun gear 304.

[0029] In some cases, the one-way bearing 402 can be replaced by other one-way locking elements such as ratchet and pawl mechanisms or overrunning clutches to adapt to different load torque and impact conditions; the fixed shaft 403 can be integrally formed with the inner ring of the one-way bearing 402 to further improve the connection rigidity and coaxiality; the limiting and fixing groove 102 can be replaced by a limiting structure with a bearing housing and a snap ring to facilitate the disassembly and maintenance of the bearing.

[0030] In some embodiments, the one-way bearing 402 is a one-way needle roller bearing or a one-way wedge bearing; the fixed shaft 403 and the sun gear 304 are separate structures, and the fixed shaft 403 and the sun gear 304 are coaxially fixedly assembled by interference fit.

[0031] Among them, one-way needle roller bearings or one-way wedge bearings are specific implementations of one-way bearing 402. One-way needle roller bearings rely on the wedging action of internal needle rollers to achieve locking, with a compact structure and small radial dimensions. One-way wedge bearings rely on the wedging effect of internal wedges to achieve locking, with stronger load-bearing capacity and better impact resistance. Both allow only unidirectional rotation of the inner ring relative to the outer ring, and lock immediately in the opposite direction. The fixed shaft 403 and the sun gear 304 are separate structures, which are processed independently and do not need to be integrally formed, which can reduce the processing difficulty. The two are coaxially fixed by interference fit, and the elastic deformation of the material generates a clamping force on the mating surface. After assembly, there is no relative rotation, and torque can be transmitted synchronously.

[0032] During implementation, when the sun gear 304 exhibits a reverse rotation tendency, the needle roller / wedge immediately weds between the inner and outer rings, locking without backlash and responding rapidly. The reverse torque can be stably transmitted to the housing 1, ensuring reliable fixation of the sun gear 304 and enabling the planetary mechanism to stably output a reduction ratio of 1:1.8. When the sun gear 304 moves in the forward direction, the needle roller / wedge is in a relaxed state, with minimal rotational resistance in the inner ring. The hydraulic drag torque is sufficient to drive the sun gear 304 to rotate synchronously, ensuring sensitive speed ratio switching. The separate interference fit connection method ensures that the fixed shaft 403 and the sun gear 304 rotate synchronously. The system operates in one step without relative sliding, ensuring lossless torque transmission. The one-way needle roller bearing in this solution has the advantages of small radial dimensions and compact structure, making it suitable for narrow installation spaces. The one-way wedge bearing has the advantages of strong load-bearing capacity and good impact resistance, making it suitable for heavy-duty impact conditions. Both are mature standard parts with low procurement costs and good interchangeability. The split processing reduces the processing difficulty of the 304 sun gear, reduces material waste and processing scrap rate from one-piece molding, and the interference fit connection method does not require additional fasteners. The structure is compact, the connection is reliable, and it can ensure high coaxiality and smooth transmission.

[0033] In some cases, the connection between the fixed shaft 403 and the sun gear 304 can be replaced by a key connection, spline connection, or lock nut fixing, to adapt to different torque levels and disassembly / assembly requirements; other types of one-way bearings 402, such as one-way ball bearings, can be selected according to working conditions to adapt to different speeds and precision requirements; a positioning step can be added to the mating surface between the fixed shaft 403 and the sun gear 304 to further improve the axial positioning accuracy of the press-fitting.

[0034] In some embodiments, one axial end face of the sun gear 304 is provided with an annular groove 305, and the other axial end face is a plane; the corresponding mating end face of the planet carrier 303 is provided with an annular boss 306 adapted to the annular groove 305; an axial gap is left between the two axial end faces of the sun gear 304 and the mating end faces of the planet carrier 303 and filled with transmission oil to form the annular oil gap 401; the annular boss 306 extends into the annular groove 305, and a mating gap is left between the annular boss 306 and the inner wall of the annular groove 305, and the mating gap is connected to the axial gap on that side.

[0035] The sun gear 304 has an annular groove 305 on one side of its axial end face to accommodate an annular boss 306, increasing the contact area between the oil and the sun gear 304 and enhancing the oil drag torque. The other side of the sun gear 304's axial end face is flat, without any concave or convex structures, forming a basic planar oil gap with the end face of the planetary carrier 303, providing basic oil shearing action and reducing processing costs. The corresponding end face of the planetary carrier 303 has an annular boss 306 that matches the annular groove 305. When the planetary carrier 303 rotates synchronously with the planetary carrier 303, it agitates the oil in the groove, generating fluid shearing force. Axial gaps are left between the two end faces of the sun gear 304 and the mating end faces of the planetary carrier 303, and these gaps are filled with transmission oil, forming a complete annular oil gap 401. To ensure that the sun gear 304 can rotate freely without contacting or rubbing against the planetary carrier 303, the annular boss 306 extends into the annular groove 305, forming a fitting clearance between their inner walls. This fitting clearance is interconnected with the axial clearance on the same side, which expands the oil's effective area and enhances the oil's dragging effect. When the planetary carrier 303 rotates with the outer gear ring 301, it drives the transmission oil in the axial clearances on both sides to flow synchronously. The oil on the planar side generates a basic dragging torque through end-face shearing. On the side with the groove, in addition to the basic shearing force of the end-face axial clearance, the annular boss 306, when rotating with the planetary carrier 303, agitates the oil in the fitting clearance, generating additional radial and axial shearing forces, further increasing the dragging torque acting on the sun gear 304.

[0036] During implementation, under heavy load conditions, the load resistance is greater than the hydraulic drag torque, so the sun gear 304 remains locked, and the planetary mechanism outputs at a reduction ratio of 1:1.8. Under light load conditions, the hydraulic drag torque overcomes the load resistance, driving the sun gear 304 to rotate synchronously. The mechanism switches to direct drive mode, and the mating clearance and axial clearance are connected, ensuring the circulation of hydraulic fluid while also providing lubrication and heat dissipation. This solution adopts a single-sided convex-concave mating structure, which, while ensuring sufficient drag torque, only requires machining the groove and boss on one side, significantly reducing machining difficulty and manufacturing costs. The connection between the mating clearance and axial clearance expands the working area of ​​the hydraulic fluid and the sun gear 304, improving the stability of the drag torque and ensuring that the sun gear 304 can stably follow the movement under light load conditions, avoiding shifting failure. Axial clearances are provided on both sides and filled with transmission oil, which makes the axial force on the sun gear 304 balanced and the operation smoother. At the same time, the hydraulic fluid can fully lubricate the mating end faces of the sun gear 304 and the planetary carrier 303, reducing wear.

[0037] In some embodiments, the planetary carrier 303 includes a first planetary end cap 307, a second planetary end cap 308, and an inner support 309; the outer gear ring 301 is fixedly disposed on the periphery of the first planetary end cap 307 and the second planetary end cap 308; the planetary gear 302 is rotatably mounted on the inner support 309, and the inner support 309 is coaxially fixedly connected to the output shaft 310; the annular boss 306 is disposed on the inner end face of the first planetary end cap 307, the side of the sun gear 304 with the annular groove 305 is arranged facing the first planetary end cap 307, and the planar side of the sun gear 304 is arranged facing the end face of the inner support 309.

[0038] The first planetary end cap 307 and the second planetary end cap 308 are respectively arranged on both sides of the planetary mechanism. Rotary bearings are installed on the outer circumference of both end caps, and they are rotatably supported on the inner wall of the housing 1 via these bearings, providing coaxial rotational support for the planetary carrier 303 as a whole. Simultaneously, the end caps are used to fix the external gear ring 301, providing axial restraint for the planetary gears 302 and the sun gear 304, forming the outer support structure of the planetary carrier 303. The inner support 309 is located inside the planetary carrier 303, used to install the planetary gears 302, bearing the revolution of the planetary gears 302 and transmitting it to the output shaft 310. It is the core load-bearing and torque output component of the planetary carrier 303. The external gear ring 301 is fixed to the periphery of the two end caps, so that the external gear ring 301 and the two planetary end caps are coaxially aligned. The planetary gear 302 is rotatably mounted on the inner support 309 and can rotate freely on the inner support 309, while simultaneously driving the inner support 309 to revolve, thus achieving power reduction transmission. The inner support 309 is coaxially fixed to the output shaft 310, directly transmitting the revolution torque of the planetary carrier 303 to the output shaft 310 for outward output. The annular boss 306 is set on the inner end face of the first planetary end cover 307, so that the boss rotates synchronously with the outer gear ring 301 and the planetary end cover, ensuring a stable relative speed difference with the groove of the sun gear 304. The grooved side of the sun gear 304 faces the first planetary end cover 307, and the flat side faces the end face of the inner support 309, ensuring that the oil gap structure corresponds one-to-one and the dragging effect is stable.

[0039] During implementation, power is transmitted through the power input device to drive the external gear ring 301 to rotate. The external gear ring 301 drives the first and second planetary end caps 308 to rotate synchronously. Simultaneously, the external gear ring 301 meshes with and drives each planet gear 302 to rotate. While the planet gears 302 revolve around the sun gear 304, they also drive the inner support 309 to revolve around its axis. The inner support 309 drives the output shaft 310 to rotate and output power outward. Under heavy load conditions, the sun gear 304 is locked, the planet gears 302's revolution speed is reduced, and the inner support 309 rotates at a speed of 1:1.8. The reduction ratio outputs high torque; under light load conditions, the annular boss 306 on the first planetary end cap 307 rotates at high speed with the end cap, stirring the oil in the groove to generate a dragging torque, driving the sun gear 304 to rotate synchronously, and finally making the planetary carrier 303 and the sun gear 304 operate synchronously, entering the direct drive mode; this solution adopts a split planetary carrier 303 structure that can be disassembled and processed, each component has good manufacturability, the processing difficulty is much lower than that of the integral planetary carrier 303, and the yield is high. The outer gear ring 301 is fixed to the outer periphery of the two end caps, the connection is firm and the positioning is accurate, which can ensure the coaxiality of the outer gear ring 301 and the planetary carrier 303, reduce meshing off-center load, the inner support 309 independently bears the planetary gear 302 and the output torque, the structure has good rigidity, the load distribution is uniform, the load-bearing capacity is strong, and the annular boss 306 is integrated on the planetary end cap, without the need for additional parts, the structure is compact, the space utilization is high, and the assembly process is few.

[0040] In some cases, the planetary carrier 303 can adopt an integral casting structure to further improve structural rigidity and adapt to high torque and heavy load conditions; the external gear ring 301 can adopt an integral molding structure with the first and second planetary end caps 308 to reduce assembly links and improve connection strength; the inner support 309 and the output shaft 310 can adopt an integral molding structure to shorten the power transmission path and improve transmission rigidity.

[0041] In some embodiments, the axial end face clearance between the sun gear 304 and the planet carrier 303 is 0.1~0.5mm.

[0042] The axial end face clearance is the axial distance between the mating end faces of the sun gear 304 and the planetary carrier 303. It is the basic dimension for forming the annular oil gap 401. The clearance size directly determines the shear strength and drag torque of the oil. If the clearance is too small, the oil flow resistance will be large and the viscosity loss will be high, which will increase the transmission power loss. If the clearance is too large, the shear effect of the oil will be weakened and it will not be able to generate enough drag torque to drive the sun gear 304 to rotate, which will lead to shifting failure under light load conditions. The axial end face clearance is controlled within the range of 0.1~0.5mm, which matches the kinematic viscosity of conventional industrial transmission oil.

[0043] During implementation, under heavy load conditions, the sun gear 304 is locked, and the planetary carrier 303 rotates relative to the sun gear 304 at a reduction ratio of 1:1.8. This clearance size ensures that the oil forms a stable lubricating film, avoiding contact wear between the end faces of the sun gear 304 and the planetary carrier 303, while keeping viscous loss within a reasonable range. Under light load conditions, the planetary carrier 303's speed increases, and the oil within this clearance generates a stable fluid shear force. The dragging torque is sufficient to overcome the rotational resistance of the sun gear 304, driving it to rotate synchronously and ensuring reliable speed ratio switching. In high and low temperature environments, this clearance size can adapt to changes in oil viscosity, ensuring stable shifting performance over a wide temperature range. A clearance range of 0.1~0.5mm balances the oil dragging torque and viscous loss, ensuring sufficient drag force for shifting under light load conditions while avoiding additional transmission losses. The quantified clearance size ensures consistency in mass production, keeping the shifting load threshold uniform across different products and avoiding individual differences. This clearance size is compatible with the viscosity range of conventional transmission oils. It can operate stably within a wide temperature range of 20℃ to 80℃, improving the environmental adaptability of the device.

[0044] In some embodiments, a support bearing 311 is installed between the output shaft 310 and the housing 1; the planetary gears 302 are rotatably mounted on the planet carrier 303 via planetary pins, and each planetary gear 302 is distributed at equal intervals along the circumferential direction.

[0045] The support bearing 311 is installed between the output shaft 310 and the housing 1. Its core function is to provide radial rotational support for the output shaft 310, bear the radial load when the output shaft 310 is running, ensure the coaxiality of the output shaft 310, and reduce rotational friction resistance. The support bearing 311 only plays a supporting role and does not have a one-way locking function to avoid interference with speed ratio switching. The planetary pin is inserted through the center of the planetary gear 302 and rotatably mounts the planetary gear 302 on the planet carrier 303, providing rotational support for the planetary gear 302 to ensure that the planetary gear 302 can rotate freely. The planetary gears 302 are evenly distributed along the circumferential direction so that the meshing load is evenly distributed to each planetary gear 302 and avoids local load concentration.

[0046] During implementation, when the output shaft 310 drives the planetary carrier 303 to rotate, the support bearing 311 radially limits the output shaft 310, ensuring the coaxiality of the output shaft 310 and the housing 1, reducing operational vibration and noise. The planetary gears 302 rotate around their planetary pins and simultaneously revolve around the sun gear 304, transmitting the power of the external gear ring 301 to the planetary carrier 303. The evenly spaced structure ensures that each planetary gear 302 experiences a consistent meshing force, resulting in balanced force distribution on the planetary carrier 303. Under heavy-load conditions, the ratio is 1:1.8. The high torque from the reduction ratio is evenly distributed to each planetary gear 302, resulting in a stronger overall load-bearing capacity. Under light-load direct-drive conditions, the planetary gears 302 do not rotate, the load is evenly distributed, and the operation is more stable. In this solution, the support bearing 311 can significantly reduce the rotational friction resistance of the output shaft 310, improve transmission efficiency, and at the same time ensure the operating accuracy of the output shaft 310 and reduce radial runout. The planetary pin shaft has a simple structure, is easy to assemble, and rotates flexibly, ensuring the smooth rotation of the planetary gears 302. The evenly spaced distribution of the planetary gears 302 can evenly distribute the load, avoid local stress concentration, effectively improve the overall load-bearing capacity and service life of the planetary gear mechanism 3, and at the same time reduce operating noise and vibration.

[0047] In some cases, the support bearing 311 can be selected from different types such as deep groove ball bearings and tapered roller bearings according to load requirements, to adapt to different stress conditions such as radial load and axial load; needle roller bearings can be added between the planetary pin shaft and the planetary gear 302 to further reduce the self-rotation friction resistance of the planetary gear 302 and improve the transmission efficiency; the number of planetary gears 302 can be adjusted according to the load requirements, such as setting 4 or 5 planetary gears 302 to further improve the load-bearing capacity of the mechanism.

[0048] In some embodiments, the housing 1 includes a first housing end cap 103 and a second housing end cap 104. The first housing end cap 103 and the second housing end cap 104 are joined together to form a sealed transmission receiving cavity. The power input device, the planetary gear mechanism 3 and the one-way locking mechanism 4 are all housed in the transmission receiving cavity.

[0049] The first housing end cap 103 and the second housing end cap 104 are two components of the housing 1. After being joined together, they form the complete main body of the housing 1, providing an installation reference and protective shell for all internal transmission components. After the two end caps are joined together, they form a sealed transmission cavity, which is used to accommodate all moving components such as the planetary gear mechanism 3 and the one-way locking mechanism 4, while sealing the internal transmission oil to prevent oil leakage.

[0050] During assembly, all internal transmission components are installed on the corresponding positions of one end cover, and then the other end cover is snapped together and locked with fasteners to form a complete sealed housing 1. During operation, the sealed cavity ensures that the transmission oil remains inside the cavity, fully lubricating each gear and bearing, achieving continuous lubrication and heat dissipation, while isolating external dust, moisture and impurities to prevent internal parts from rusting and wearing. Whether in 1:1.8 reduction mode or direct drive mode, the sealed cavity provides a stable working environment for the internal mechanism. This solution adopts a split two-end cover structure to facilitate the assembly, debugging and subsequent maintenance of internal components, resulting in high production assembly efficiency and convenient disassembly and repair. The sealed transmission cavity can effectively prevent transmission oil leakage, ensure stable oil level and lubrication effect, and prevent oil from polluting the external environment. The mating housing 1 structure can effectively isolate external contaminants, protect internal precision transmission components, and improve the protection level and service life of the device.

[0051] The present invention provides an electric vehicle, including the planetary gearbox described above.

[0052] This solution describes an electric vehicle equipped with the aforementioned planetary reducer. The electric vehicle uses the planetary reducer as the core component of its power transmission. The power output from motor 2 is transmitted to the vehicle's wheels or running gear after the planetary reducer adjusts the speed and torque, driving the vehicle. The planetary reducer can automatically switch speed ratios according to the vehicle's load. When the vehicle is heavily loaded climbing or starting fully loaded, the load resistance is high, and the planetary reducer automatically switches to a 1:1.8 reduction and torque-increasing mode, outputting high torque to drive the vehicle. When the vehicle is lightly loaded and traveling at a constant speed on a flat road, the load resistance is low, and the planetary reducer automatically switches to a 1:1 direct drive mode to reduce transmission losses. When the vehicle is coasting downhill, the one-way locking mechanism 4 remains unlocked, preventing the wheels from dragging motor 2 in the opposite direction, resulting in low coasting resistance. This electric vehicle, through the automatic transmission function of the planetary reducer, balances heavy-load climbing ability with flat-road driving efficiency, providing strong power when fully loaded and a long unloaded range, exhibiting excellent overall performance. (Single motor 2 + ...) The purely mechanical automatic shifting architecture simplifies the structure of the vehicle's electronic control system, resulting in a low failure rate and low maintenance costs. It is well-suited for the needs of civilian electric vehicles. The planetary reducer has a compact overall structure and small size, making it easy to install in the limited space of the vehicle chassis. It is also suitable for the layout requirements of small electric vehicles such as electric tricycles and low-speed four-wheeled vehicles.

[0053] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A planetary gear reducer, characterized in that, include: Power input device; A planetary gear mechanism, comprising an external gear ring, several planet gears, a planet carrier, and a sun gear; The external gear ring is connected to the power input device for transmission, the output shaft is coaxially fixed on the planet carrier, and the sun gear is rotatably and coaxially disposed inside the planet carrier and meshes with each planet gear. A one-way locking mechanism is provided, which cooperates with the sun gear drive to restrict only the one-way rotation of the sun gear; the axial end face of the sun gear and the axial end face of the corresponding position of the planet carrier cooperate to form an annular oil gap, which is filled with transmission oil.

2. The planetary reducer according to claim 1, characterized in that, The power input device includes a motor, a motor wheel, and a transition gear. The motor wheel is coaxially fixed to the output end of the motor. The motor wheel meshes with the transition gear, and the transition gear meshes with the external teeth of the external gear ring.

3. The planetary reducer according to claim 1, characterized in that, It also includes a housing, and the one-way locking mechanism includes a one-way bearing and a fixed shaft; a limiting fixing groove is formed in the inner wall of the housing, the outer ring of the one-way bearing is circumferentially fixed in the limiting fixing groove, one end of the fixed shaft is coaxially fixed to the inner ring of the one-way bearing, and the other end is coaxially fixed to the sun gear.

4. The planetary reducer according to claim 3, characterized in that, The one-way bearing is a one-way needle roller bearing or a one-way wedge bearing; the fixed shaft and the sun gear are separate structures, and the fixed shaft and the sun gear are coaxially fixedly assembled by interference fit.

5. The planetary reducer according to claim 1, characterized in that, The sun gear has an annular groove on one axial end face and a flat surface on the other axial end face; the planet carrier has an annular boss that matches the annular groove on the corresponding mating end face; there is an axial gap between the two axial end faces of the sun gear and the mating end faces of the planet carrier, which is filled with transmission oil to form the annular oil gap; the annular boss extends into the annular groove, and there is a mating gap between the annular boss and the inner wall of the annular groove, which is connected to the axial gap on that side.

6. The planetary reducer according to claim 5, characterized in that, The planetary carrier includes a first planetary end cap, a second planetary end cap, and an inner support; the outer gear ring is fixedly disposed around the first planetary end cap and the second planetary end cap; the planetary gears are rotatably mounted on the inner support, and the inner support is coaxially fixedly connected to the output shaft; the annular boss is disposed on the inner end face of the first planetary end cap, the side of the sun gear with the annular groove is arranged facing the first planetary end cap, and the flat side of the sun gear is arranged facing the end face of the inner support.

7. The planetary reducer according to claim 1, characterized in that, The axial end face clearance between the sun gear and the planet carrier is 0.1~0.5mm.

8. The planetary reducer according to claim 3, characterized in that, A support bearing is installed between the output shaft and the housing; the planetary gears are rotatably mounted on the planet carrier via planetary pins, and each planetary gear is distributed at equal intervals along the circumference.

9. The planetary reducer according to claim 3, characterized in that, The housing includes a first housing end cover and a second housing end cover. The first housing end cover and the second housing end cover are joined together to form a sealed transmission cavity. The planetary gear mechanism and the one-way locking mechanism are housed in the transmission cavity, and the output shaft extends out of the first housing end cover.

10. An electric vehicle, characterized in that, Includes the planetary gearbox as described in any one of claims 1 to 9.

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