Differential lubrication system, differential and method for determining the angle of inclination α

Abstract

The application provides a kind of transfer lubrication system, transfer and the determination method of inclination angle α, comprising: transfer housing, the main oil pool for accommodating lubricating oil is arranged in transfer housing inside;Chain and sprocket assembly, chain and sprocket assembly is located in transfer housing, part of chain and sprocket assembly is arranged in main oil pool, chain and sprocket assembly is used to stir lubricating oil in the process of rotation;Oil storage cavity, oil storage cavity is arranged in the side of chain and sprocket assembly away from main oil pool, and oil storage cavity is communicated with main oil pool arrangement;Wherein, the bottom surface of oil storage cavity has preset inclination angle α relative to horizontal plane, and the opening of oil storage cavity is towards the rotation tangent direction of chain and sprocket assembly. To solve the problem that the total amount of lubricating oil is fixed and the liquid level cannot be adjusted in the prior art, which leads to insufficient heat dissipation and easy to cause friction plate overheating failure at low speed and high load.

Description

Technical Field

[0001] This invention relates to the field of transfer case lubrication system technology, and more specifically, to a transfer case lubrication system, a transfer case, and a method for determining the tilt angle α. Background Technology

[0002] In existing technologies, the total lubricating oil capacity of the on-demand transfer case in traditional four-wheel drive vehicles is fixed, resulting in a performance contradiction between "low-speed high-load" and "high-speed cruising" conditions: when getting out of trouble at low speeds or climbing at extreme speeds, the multi-plate clutch generates a large amount of heat due to slippage. The heat capacity of the fixed oil volume is limited, causing the oil temperature to rise rapidly and the viscosity to drop, leading to overheating and erosion of the friction plates or triggering thermal protection to disconnect the four-wheel drive, resulting in failure to get out of trouble; while when cruising at high speeds on highways, the high-speed rotation of the sprocket and chain agitates the lubricating oil, generating severe churning resistance. This not only consumes engine power and increases fuel consumption, but the heat generated by churning also unnecessarily accelerates oil deterioration, reducing transmission efficiency and system reliability.

[0003] There is currently no effective solution to the aforementioned technical problems. Summary of the Invention

[0004] The main objective of this invention is to provide a transfer case lubrication system, a transfer case, and a method for determining the tilt angle α, in order to solve the problem in the prior art where the total amount of lubricating oil in a traditional transfer case is fixed and the oil level is not adjustable, resulting in insufficient heat dissipation at low speeds and high loads, which easily leads to overheating and failure of the friction plates.

[0005] To achieve the above objectives, according to one aspect of the present invention, a transfer case lubrication system is provided, comprising: a transfer case housing, wherein a main oil reservoir for containing lubricating oil is provided inside the transfer case housing; a sprocket and chain assembly located inside the transfer case housing, a portion of the sprocket and chain assembly being disposed within the main oil reservoir, the sprocket and chain assembly being used to agitate the lubricating oil during rotation; and an oil reservoir cavity disposed on the side of the sprocket and chain assembly away from the main oil reservoir, and the oil reservoir cavity being connected to the main oil reservoir; wherein the bottom surface of the oil reservoir cavity has a predetermined inclination angle α relative to the horizontal plane, and the opening of the oil reservoir cavity faces the rotational tangent direction of the sprocket and chain assembly.

[0006] Furthermore, the bottom surface of the oil storage cavity is designed as a curved surface, and the length of the oil storage cavity is smaller than the length of the chain in the sprocket and chain assembly.

[0007] Furthermore, the tilt angle α ranges from 0° to 45°.

[0008] Furthermore, the oil storage chamber is located above the main oil tank, and the vertical distance between the bottom of the oil storage chamber and the liquid surface of the main oil tank is 0mm~200mm.

[0009] Furthermore, an open channel is formed inside the oil storage cavity, which includes an oil inlet channel and an oil return channel. The opening of the oil inlet channel faces the rotational tangent of the sprocket and chain assembly and is located at the oil inlet end of the oil storage cavity. The opening of the oil return channel is located at the oil return end of the oil storage cavity and is lower than the vertical projection position of the opening of the oil inlet channel, so as to utilize gravity to achieve natural return of lubricating oil.

[0010] Furthermore, the oil inlet channel and the oil return channel are set up independently, or the oil inlet channel and the oil return channel are integrated into a connecting flow channel.

[0011] Furthermore, the oil reservoir is integrally cast with the transfer case housing, or the oil reservoir is a separate component independent of the transfer case housing, and the inner wall of the oil reservoir is detachably connected to the transfer case housing.

[0012] Furthermore, the transfer case lubrication system also includes a variable fluid level auxiliary module, which includes a level sensor, an electronic oil pump, and a control unit located in the main oil sump. The level sensor is used to monitor the lubricating oil level in real time and transmit the signal to the control unit. The control unit controls the electronic oil pump to actively pump the lubricating oil between the oil reservoir and the main oil sump according to the vehicle operating conditions and the level signal, so as to achieve fine adjustment of the amount of lubricating oil in the main oil sump.

[0013] According to another aspect of the present invention, a method for determining the tilt angle α of a transfer case lubrication system as described in any of the above claims is provided, comprising: establishing a three-dimensional model of the transfer case lubrication system; generating a comprehensive performance evaluation index based on the lubricating oil temperature rise under low-speed traction conditions and the reduction in churning torque under high-speed cruising conditions; and iteratively optimizing the initial tilt angle based on the comprehensive performance evaluation index to determine the optimal value as the target tilt angle α.

[0014] According to another aspect of the present invention, a transfer case is provided, the transfer case having a transfer case lubrication system, the transfer case lubrication system being the transfer case lubrication system described above.

[0015] By applying the technical solution of this invention, an oil storage chamber is provided on the side of the sprocket and chain assembly away from the main oil sump inside the transfer case housing. A passive dynamic fluid level adjustment mechanism is constructed by utilizing the preset tilt angle of the bottom surface of the oil storage chamber and its opening facing the tangential direction of sprocket rotation. Under low-speed, high-load conditions, the sprocket's churning kinetic energy is weak, and the lubricating oil flows back to the main oil sump by gravity through the tilted bottom surface, maintaining a high fluid level in the main oil sump. This ensures sufficient lubrication and heat dissipation of the friction plates and increases the system's heat capacity. Under high-speed cruising conditions, the high dynamic pressure jet generated by the high-speed rotation of the sprocket rapidly pumps the lubricating oil to the oil storage chamber for temporary storage, causing the fluid level in the main oil sump to drop. This reduces the chain's immersion depth, significantly reducing churning resistance and parasitic power loss, achieving the beneficial effects of improving transmission efficiency, reducing oil consumption, and suppressing abnormal oil temperature rise. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A schematic diagram of an embodiment of the transfer case lubrication system according to the present invention is shown;

[0018] Figure 2 A flowchart illustrating an embodiment of the method for determining the tilt angle α according to the present invention is shown.

[0019] The above figures include the following reference numerals:

[0020] 1. Transfer case housing;

[0021] 2. Main oil tank;

[0022] 3. Sprocket and chain assembly; 31. Sprocket; 32. Chain;

[0023] 4. Oil storage cavity;

[0024] 5. Open channel; 51. Oil inlet channel; 52. Oil return channel. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of layers and regions may be exaggerated, and the same reference numerals are used to denote the same devices, and therefore their description will be omitted.

[0029] Combination Figure 1 As shown, according to a specific embodiment of this application, a transfer case lubrication system is provided.

[0030] Specifically, the transfer case lubrication system includes:

[0031] Transfer case 1, with a main oil sump 2 inside for holding lubricating oil;

[0032] The sprocket and chain assembly 3 is located inside the transfer case housing 1. Part of the sprocket and chain assembly 3 is located in the main oil sump 2. The sprocket and chain assembly 3 is used to agitate the lubricating oil during rotation.

[0033] Oil storage chamber 4 is located on the side of sprocket and chain assembly 3 away from main oil tank 2, and oil storage chamber 4 is connected to main oil tank 2.

[0034] The bottom surface of the oil storage cavity 4 has a preset tilt angle α relative to the horizontal plane, and the opening of the oil storage cavity 4 faces the rotational tangent direction of the sprocket and chain assembly 3.

[0035] The transfer case housing 1 defines a main oil sump 2 for containing lubricating oil, serving as the basic oil storage area for the lubrication system. The sprocket and chain assembly 3 is located inside the transfer case housing 1, with some components immersed in the lubricating oil in the main oil sump 2. Its main function is to splash lubricate by agitating the lubricating oil during rotation.

[0036] Specifically, the oil storage chamber 4 is located on the side of the sprocket and chain assembly 3 away from the main oil tank 2, i.e., above the liquid surface of the main oil tank. The oil storage chamber 4 and the main oil tank 2 are interconnected through an open channel. No valves or moving parts are installed in this connection path to ensure passive free flow of fluid. The oil storage chamber 4 has specific structural features. Its bottom surface has a preset inclination angle α relative to the horizontal plane. This inclination design creates a gravitational potential energy gradient within the oil storage chamber 4, pointing from the oil inlet to the oil return end, which promotes the natural return of lubricating oil along the bottom surface under the action of gravity. At the same time, the opening of the oil storage chamber 4 faces the rotational tangent direction of the sprocket and chain assembly 3. This orientation allows the oil jet generated when the sprocket and chain assembly rotates to directly and efficiently impact or enter the oil storage chamber. The dynamic pressure of the lubricating oil is used to pump the oil into the oil storage chamber 4, thereby realizing the automatic dynamic distribution of lubricating oil between the main oil tank and the oil storage chamber based on the difference in rotational speed.

[0037] Specifically, the sprocket and chain assembly 3 consists of two sprockets 31 and a chain 32, with the chain 32 rotating between the two sprockets.

[0038] By applying the technical solution of this invention, an oil storage chamber 4 is provided on the side of the sprocket and chain assembly 3 away from the main oil sump 2 inside the transfer case housing 1. A passive dynamic liquid level adjustment mechanism is constructed by utilizing the preset tilt angle of the bottom surface of the oil storage chamber 4 and its opening facing the tangential direction of sprocket rotation. Under low-speed, high-load conditions, the sprocket's churning kinetic energy is weak, and the lubricating oil flows back to the main oil sump by gravity through the tilted bottom surface, maintaining a high liquid level in the main oil sump. This ensures sufficient lubrication and heat dissipation of the friction plates and increases the system's heat capacity. Under high-speed cruising conditions, the high dynamic pressure jet generated by the high-speed rotation of the sprocket rapidly pumps the lubricating oil to the oil storage chamber for temporary storage, causing the liquid level in the main oil sump to drop. This reduces the chain's immersion depth, significantly reducing churning resistance and parasitic power loss, achieving the beneficial effects of improving transmission efficiency, reducing oil consumption, and suppressing abnormal oil temperature rise.

[0039] Furthermore, the bottom surface of the oil storage cavity 4 is set as a circular arc surface, and the length of the oil storage cavity 4 is smaller than the length of the chain 32 of the sprocket and chain assembly 3.

[0040] The bottom surface of the oil storage cavity 4 is designed as a curved surface. This curved surface structure not only conforms to the characteristics of fluid dynamics to guide the smooth flow of lubricating oil, but also effectively avoids oil accumulation or flow resistance that may be caused by right angles or planes, ensuring that the lubricating oil can flow smoothly from the oil inlet end to the oil return end along the curved surface under the action of gravity.

[0041] The length of the oil reservoir 4 is set to be smaller than the total length of the chain 32 in the sprocket and chain assembly 3. This structural layout ensures that the oil reservoir can be compactly adapted to the specific oil-throwing area of ​​the sprocket and chain. This ensures that the oil inlet can fully receive the oil jet generated by the high-speed rotating chain, while avoiding the oil reservoir from being too large and occupying too much non-functional space. Thus, efficient lubricating oil storage and return functions are achieved within the limited housing space, maintaining the compactness and rationality of the transfer case's internal structure.

[0042] Furthermore, the tilt angle α ranges from 0° to 45°.

[0043] The preset tilt angle α of the bottom surface of the oil reservoir 4 is limited to the range of 0° to 45°. This angle is a key engineering parameter that determines the dynamic performance of the transfer case lubrication system. Its specific value needs to be determined through iterative optimization using fluid simulation combined with bench tests. If the tilt angle α is too small, i.e., the bottom surface is too gentle, the gravity driving force for the lubricating oil to flow back along the bottom surface under low-speed conditions is insufficient, which may cause the lubricating oil to be undesirably trapped in the oil reservoir, thereby causing an abnormal drop in the main oil sump level and weakening the heat dissipation conditions of the friction plates. Conversely, if the tilt angle α is too large, i.e., the bottom surface is too steep, the lubricating oil will flow back too quickly under high-speed conditions, making it difficult to form an effective liquid surface temporary storage effect in the oil reservoir. This will result in insufficient drop in the main oil sump level, failing to adequately reduce the chain immersion depth, and thus weakening the suppression effect on churning losses. Therefore, by comprehensively considering the friction plate temperature rise index under low-speed traction conditions and the reduction of oil churning torque under high-speed cruising conditions, a comprehensive performance evaluation index is constructed using weighting coefficients. The optimal tilt angle α is selected within the range of 0° to 45° to achieve the best balance between heat dissipation capacity and transmission efficiency of the lubrication system.

[0044] Furthermore, the oil storage chamber 4 is located above the main oil tank 2, and the vertical distance between the bottom of the oil storage chamber 4 and the liquid surface of the main oil tank 2 is 0mm~200mm.

[0045] Specifically, the vertical distance between the bottom of the oil storage chamber 4 and the stable liquid level of the main oil sump 2 under static or low-speed conditions is limited to the range of 0mm to 200mm. This distance range is designed to balance return efficiency and structural compactness. If the distance is too large, it may lead to excessively fast return oil flow at low speeds or waste of structural space. If the distance is too small, or even 0mm, it may affect the dynamic stability of the liquid level in the main oil sump or cause structural interference. This specific vertical distance, together with the inclined bottom surface, ensures that the lubricating oil can return in a timely and smooth manner under low-speed conditions to maintain a high liquid level in the main oil sump. Under high-speed conditions, it can precisely control the amount of temporary oil stored in the oil storage chamber and the drop in the liquid level of the main oil sump based on the dynamic balance between the inlet flow rate and the gravity return flow rate, thereby achieving adaptive adjustment to the lubrication and heat dissipation requirements under different operating conditions.

[0046] Furthermore, an open channel 5 is formed inside the oil storage cavity 4. The open channel includes an oil inlet channel 51 and an oil return channel 52. The opening of the oil inlet channel 51 faces the rotational tangent of the sprocket and chain assembly 3 and is located at the oil inlet end of the oil storage cavity 4. The opening of the oil return channel 52 is located at the oil return end of the oil storage cavity 4 and is lower than the vertical projection position of the opening of the oil inlet channel 51, so as to utilize gravity to achieve natural return of lubricating oil.

[0047] The interior of the oil storage chamber 4 is structurally arranged to form an open channel 5, which allows for bidirectional flow of lubricating oil between the main oil sump 2 and the oil storage chamber 4 without the need for any valves or moving parts. The open channel 5 is specifically divided into an inlet channel 51 at one end of the oil storage chamber 4 and a return channel 52 at the other end. The opening of the inlet channel 51 faces directly towards the rotational tangent of the sprocket and chain assembly 3. This specific orientation allows the oil jet generated when the sprocket and chain rotate and agitate the lubricating oil to directly impact and flow into the inlet channel with minimal resistance. Especially under high-speed conditions, the dynamic pressure of the high-speed oil flow "pumps" a large amount of lubricating oil into the oil storage chamber. The return channel 52 is located at the opposite end of the oil storage chamber 4 (i.e., the return end), and the vertical projection of its opening is lower than the opening of the inlet channel 51. This staggered layout, combined with the inclination angle α of the bottom surface of the oil storage chamber, creates a clear gravitational potential energy gradient. Under low-speed conditions, the amount of lubricating oil entering the oil storage chamber is small and the dynamic pressure is low. Under the action of gravity, the lubricating oil flows smoothly along the inclined bottom surface to the lower-positioned return oil channel 52 and naturally flows back to the main oil sump, realizing the dynamic balance between oil inlet and return, and ensuring that the main oil sump maintains a high liquid level to ensure heat dissipation. Under high-speed conditions, although there is a gravity return path, the huge oil inlet flow and dynamic pressure cause the liquid level in the chamber to rise rapidly until the static pressure head generated by the liquid level height is sufficient to drive the lubricating oil to flow out through the return oil channel 52, thereby realizing the temporary storage of lubricating oil in the oil storage chamber and the drop of the liquid level in the main oil sump.

[0048] Furthermore, the oil inlet channel 51 and the oil return channel 52 are set independently, or the oil inlet channel 51 and the oil return channel 52 are an integrated connecting channel.

[0049] In one specific embodiment, the oil storage cavity 4 has two independent oil inlet channels 51 and 52. Specifically, the oil inlet channel 51 is located at the oil inlet end of the oil storage cavity 4, and its opening faces directly towards the rotational tangent of the sprocket and chain assembly 3, for receiving the lubricating oil jet ejected by the high-speed rotating sprocket and chain; the oil return channel 52 is located at the oil return end of the oil storage cavity 4, and its opening is lower than the projection position of the opening of the oil inlet channel 51 in the vertical direction. These two channels are structurally separate, and they are connected to the internal space of the oil storage cavity through independent flow paths, or separated within the oil storage cavity by a specific flow guiding structure, ensuring that after the lubricating oil enters from the oil inlet end, it must flow through the bottom area of ​​the oil storage cavity with a certain slope before reaching the lower-lying oil return channel 52 and flowing back to the main oil sump. This independent configuration has a clear structure, which makes it easy to optimize the flow field distribution by adjusting the specific position and size of the two channels in the oil storage cavity. Furthermore, during manufacturing, the oil inlet and return structures can be formed separately using different molds or processing steps, reducing the difficulty of processing a single complex flow channel.

[0050] In another embodiment, the oil inlet channel 51 and the oil return channel 52 are integrated into a continuous, interconnected flow channel. Specifically, this flow channel starts from the oil inlet end of the oil storage cavity 4, extends along the internal space of the oil storage cavity 4, passes through the bottom surface region with an inclined angle α, and finally reaches the oil return end of the oil storage cavity 4. The oil inlet channel 51 and the oil return channel 52 are not two physically isolated independent channels, but rather different functional sections of the same internal flow channel system: the oil inlet end is responsible for introducing lubricating oil, the oil return end is responsible for discharging lubricating oil, and the middle part constitutes a transition area where lubricating oil is temporarily stored in the oil storage cavity and flows back under gravity. This integrated, interconnected flow channel design simplifies the internal structure of the oil storage cavity 4, reduces possible flow resistance and structural dead angles, and facilitates smooth flow and cleanliness of the lubricating oil. In manufacturing, this interconnected flow channel structure can be directly obtained through integral casting or one-piece molding processes, improving the structural strength and sealing reliability of the components, while reducing assembly processes and potential leakage risks. Regardless of the form used, the core principle is to utilize the inclined bottom surface and positional difference, combined with the difference in oil inlet dynamic pressure caused by the change in sprocket speed, to achieve passive dynamic distribution of lubricating oil between the main oil sump and the oil storage chamber.

[0051] Furthermore, the oil reservoir 4 is integrally cast with the transfer case housing 1, or the oil reservoir 4 is a separate component independent of the transfer case housing 1, and the inner wall of the oil reservoir 4 is detachably connected to the transfer case housing 1.

[0052] In one specific embodiment, the oil reservoir 4, as part of the internal structure of the transfer case housing 1, is manufactured as a single integral component with the transfer case housing 1 through an integral casting process. Specifically, during the manufacturing of the transfer case housing, the cavity for the oil reservoir 4, along with the oil inlet channel 51 and oil return channel 52 communicating with it, are pre-reserved directly inside the housing. This integral molding method eliminates any additional connection gaps or sealing surfaces between the oil reservoir 4 and the main oil sump 2, fundamentally eliminating the risk of leakage that may arise from component assembly and ensuring the sealing reliability of the lubrication system. As it is a single unit, the structure has high structural strength and rigidity, capable of withstanding the complex stress environment inside the transfer case. Furthermore, integral casting simplifies the assembly process, eliminating the need for separate fastening of the oil reservoir, thus reducing production assembly costs and time. The tilt angle α and the cavity shape can be precisely determined during the mold design stage, which helps ensure the accuracy and consistency of geometric dimensions, thereby ensuring stable lubrication performance.

[0053] In another specific embodiment, the oil reservoir 4 is designed as a separately manufactured component, detachably mounted to the inner wall of the transfer case housing 1 by bolts, clips, or other fasteners. Specifically, the oil reservoir 4 has an independent housing structure with mounting surfaces on its bottom or side walls. The mating surfaces with the inner wall of the transfer case housing 1 are sealed with gaskets or sealant and then secured with fasteners. This split design provides greater flexibility, especially during the development phase or when adapting to different vehicle models. By replacing oil reservoir components with different tilt angles α or different volumes, the characteristics of the lubrication system can be quickly adjusted without redesigning or replacing the entire transfer case housing 1. Furthermore, if blockage or wear occurs inside the oil reservoir, maintenance or replacement of this independent component can be performed, improving maintenance convenience. In some advanced embodiments, the bottom tilt angle α of this split oil reservoir can even be adjustable. By adjusting the mechanism to change its relative mounting angle with the transfer case housing 1, fine-tuning of the lubricating oil return rate can be achieved to adapt to more complex operating conditions.

[0054] Furthermore, the transfer case lubrication system also includes a variable fluid level auxiliary module, which includes a level sensor, an electronic oil pump, and a control unit located in the main oil sump 2. The level sensor is used to monitor the lubricating oil level in real time and transmit the signal to the control unit. The control unit controls the electronic oil pump to actively pump the lubricating oil between the oil storage chamber 4 and the main oil sump 2 according to the vehicle operating conditions and the level signal, so as to achieve fine adjustment of the amount of lubricating oil in the main oil sump 2.

[0055] In this embodiment, the transfer case lubrication system further integrates a variable fluid level auxiliary module. This module aims to achieve more precise adjustment of the lubricating oil level through active control, serving as a supplement or alternative to the passive tilting cavity structure. Specifically, a level sensor is installed in the main oil sump 2 to monitor the lubricating oil level in the main oil sump in real time and accurately, and transmits the collected level signal and other possible operating condition signals (such as vehicle speed, engine speed, temperature, etc.) to the control unit. The control unit, as the system's decision-making core, receives feedback signals from the level sensor and, combined with the vehicle's current operating conditions (such as low-speed high-load traction or high-speed cruising), uses algorithms to analyze and determine the ideal fluid level required. Based on this determination, the control unit sends control commands to the electronic oil pump, driving it to operate. The electronic oil pump actively pumps lubricating oil bidirectionally between the oil reservoir 4 and the main oil sump 2 according to the strength and direction of the command: when it is necessary to lower the liquid level in the main oil sump to reduce churning losses, the oil is pumped from the main oil sump to the oil reservoir for temporary storage; when it is necessary to raise the liquid level in the main oil sump to enhance heat dissipation and lubrication, the oil in the oil reservoir is pumped back to the main oil sump. This electronically controlled active adjustment mechanism allows the amount of lubricating oil in the main oil sump to be dynamically adjusted more precisely and quickly according to changes in vehicle speed and operating conditions, thereby further amplifying the beneficial effects of reducing fuel consumption, improving transmission efficiency, and optimizing heat dissipation. Although this solution increases the system complexity and cost due to sensors, actuators, control units, and wiring harnesses, and has the potential risk of electronic failure, its adjustment accuracy and response speed are superior to purely mechanical passive solutions.

[0056] The transfer case lubrication system described in this application can bring beneficial effects under different vehicle operating conditions:

[0057] (1) Low-speed escape condition

[0058] When the vehicle is in a low-speed escape condition, the linear velocity of the lubricating oil in the main oil sump, stirred by the chain, is low. The oil thrown into the inlet channel is in a discontinuous droplet or thin laminar flow state, with low dynamic pressure and low flow rate. This lubricating oil slowly flows into the inlet end of the oil reservoir. Due to the downward tilt angle α of the bottom surface of the oil reservoir, the lubricating oil entering the reservoir naturally possesses gravitational potential energy to flow towards the outlet end. Under low inlet flow conditions, the lubricating oil entering the reservoir can be promptly and smoothly discharged back to the main oil sump through the inlet channel by gravity. The inlet flow rate and the return flow rate are approximately equal, and the oil reservoir hardly retains or accumulates a large amount of lubricating oil, maintaining its internal liquid level at a low level. Therefore, the lubricating oil level in the main oil sump is almost unaffected and remains at the designed high level. This brings two key positive effects:

[0059] ① It ensures sufficient lubrication and heat dissipation of the friction plate assembly. When getting out of trouble at low speed, the friction plates experience intense sliding friction and generate a lot of heat. The high liquid level ensures that the friction plates always receive sufficient splashing or immersion oil supply, providing basic heat dissipation conditions.

[0060] ② A larger total amount of lubricating oil is allowed to be added when the vehicle leaves the factory. A larger total oil volume directly increases the total heat capacity of the system, resulting in a smaller temperature rise of the lubricating oil when absorbing the same amount of frictional heat. This effectively prevents the friction coefficient from decreasing and failing due to overheating of the friction plates, and significantly enhances the continuous off-road capability of the four-wheel drive system.

[0061] (2) High-speed cruise condition

[0062] When the vehicle enters a highway or cruises on a well-paved road, the transfer case input shaft speed increases, and the sprockets and chain rotate at high speeds. Under this condition, the splashing oil flow generated by the chain agitating the lubricating oil in the main oil sump transforms into a high-speed, continuous jet. This jet violently impacts the oil inlet of the oil reservoir with extremely high dynamic pressure, causing a large amount of lubricating oil to be "pumped" into the oil inlet channel at a flow rate far exceeding that under low-speed escape conditions, surging into the oil reservoir.

[0063] The massive influx of oil in a short period far exceeded the gravity-driven backflow rate that the inclined bottom of the oil storage chamber could drive under the current liquid level difference, causing the liquid level in the chamber to rise rapidly. Although the increased liquid level increased the head pressure difference at the return oil end, thus accelerating the return oil speed to some extent, under the continuous "high-speed ramming oil inflow," the inflow rate consistently exceeded the return flow rate. The net effect was that a large amount of lubricating oil was "retained" and temporarily stored in the oil storage chamber. This process directly resulted in a significant decrease in the liquid level of the main oil tank compared to static or low-speed conditions, and a substantial reduction in the chain's immersion depth. The resulting beneficial effects are as follows:

[0064] ① Reduce oil churning losses and improve transmission efficiency. The chain's oil churning resistance is approximately proportional to the immersion depth and the square of the rotational speed. As the main oil level drops, the chain changes from "churning a large amount of liquid oil" to "splash lubrication," drastically reducing the wasted work it does to overcome the viscous resistance of the oil, lowering parasitic power losses, and allowing more engine power to be effectively transmitted to the drive wheels, thus improving the transmission efficiency of the four-wheel drive system.

[0065] ② Suppressing unnecessary oil temperature rise. The internal frictional heat generated by oil churning is the main endogenous heat source for the transfer case oil temperature rise during high-speed cruising. This invention significantly reduces the heat generated by oil churning at the source, thus significantly slowing down the rate of oil temperature rise, avoiding abnormal oil temperature rise during cruising, and increasing the maximum operating speed of the four-wheel drive system.

[0066] ③ Reduce overall vehicle fuel consumption. Reduced churning losses and improved transmission efficiency directly translate to reduced engine load, thereby improving overall vehicle fuel economy.

[0067] ④ Automatic and reversible, with no lag. When the vehicle decelerates from high-speed cruising or re-enters a low-speed escape condition, the sprocket speed decreases, the kinetic energy of the oil slinging weakens, and the oil flow rate into the oil reservoir drops sharply. At this time, the lubricating oil temporarily stored in the reservoir continuously flows back to the main oil sump under the action of gravity through the inclined bottom surface and the return oil channel. The liquid level in the main oil sump quickly recovers to a high level, preparing sufficient heat capacity and lubrication conditions for the next low-speed, high-load condition. The entire process requires no electronic control components or mechanical valve actions; it is completed automatically and instantly based entirely on fluid dynamics characteristics, resulting in extremely high reliability.

[0068] like Figure 2 As shown, according to another aspect of the present invention, a method for determining the tilt angle α of a transfer case lubrication system as described in any of the above claims is provided, comprising:

[0069] S10. Establish a three-dimensional model of the transfer case lubrication system;

[0070] Based on the specific structural design of the transfer case lubrication system, a three-dimensional geometric model of the flow channel, including sprocket 31, chain 32, main oil sump 2, oil reservoir 4, and inlet / outlet oil channels, was established in computer-aided design software. In this model, the inclination angle α of the bottom surface of the oil reservoir was set as an adjustable parameter, and its initial value range was defined (e.g., 0° to 45°). Subsequently, the three-dimensional flow channel model was meshed to generate a high-density computational mesh (e.g., tens of millions of meshes) to accurately capture the details of the flow field. Simultaneously, the physical properties of the lubricating oil (such as the relationship between density and viscosity and temperature) were defined as fluid medium properties.

[0071] S20. A comprehensive performance evaluation index is generated based on the lubricating oil temperature rise under low-speed traction conditions and the reduction in churning torque under high-speed cruising conditions.

[0072] Specifically, the formula for calculating the comprehensive performance evaluation index is as follows:

[0073] ;

[0074] Where: F(α) – overall performance score, the higher the better;

[0075] T 升 (α) – Temperature rise of lubricating oil within a specified time under low-speed obstacle avoidance conditions (unit: °C). T 升 The smaller (α) is, the better the heat dissipation capacity and the higher the heat capacity, 1 / T 升 The larger (α) is, the higher the score for that item;

[0076] η 降 (α) — The reduction in churning torque under high-speed cruising conditions, expressed as a percentage (Example: If the churning torque decreases from 10N without the chamber). m drops to 7N m, then η 降 (α)=(10-7) / 10×100%=30%). n 降 The larger (α) is, the better the effect of improving transmission efficiency;

[0077] w1 and w2 are weighting coefficients assigned based on the vehicle's usage scenario. For example, off-road vehicles prioritize heat dissipation, so w1=0.6 and w2=0.4; highway SUVs prioritize fuel efficiency, so w1=0.3 and w2=0.7. The sum of w1 and w2 must equal 1.

[0078] In this step, two key performance evaluation indicators are defined: one is the lubricating oil temperature rise T under low-speed obstacle removal conditions. 升 (α) is used to measure the system's heat dissipation capacity; the second is the reduction in churning torque η under high-speed cruising conditions. 降 (α) is used to measure the improvement in transmission efficiency of the system. Specifically, in the simulation, low-speed conditions are simulated, and the average temperature rise of the lubricating oil within a specified time is recorded. The smaller the temperature rise, the higher the score. In the simulation of high-speed conditions, the resistance torque on the surface of the sprocket and chain is recorded, and the percentage reduction relative to the baseline state without an oil reservoir is calculated. The greater the reduction, the higher the score. Next, a comprehensive performance evaluation index formula F(α) is constructed, and weight coefficients w1 and w2 are introduced (w1+w2=1). The weights are assigned according to the main usage scenarios of the vehicle model (e.g., off-road vehicles focus on heat dissipation, while SUVs focus on fuel economy). The two indices are then weighted and fused to obtain a comprehensive performance score function that varies with the tilt angle α.

[0079] This step establishes a multi-objective optimization evaluation mechanism, avoiding the limitations of optimizing a single indicator. By quantifying the two mutually constraining performance indicators of "heat dissipation capacity" and "transmission efficiency" and assigning different weights, the optimal tilt angle can be customized according to the market positioning and usage needs of different vehicle models, making the technical solution widely applicable and targeted.

[0080] S30. Based on the comprehensive performance evaluation index, the initial tilt angle is iteratively optimized to determine the optimal value as the target tilt angle α.

[0081] Optionally, when establishing the three-dimensional geometric model of the internal flow channel of the transfer case, the inclination angle α of the bottom surface of the oil reservoir is set as a key adjustable parameter to drive the geometric changes of the model. To cover the possible engineering optimization range, the initial value range of α is set to 0° to 45°. This range covers all potential design configurations from completely horizontal (0°, mainly driven by differential pressure) to relatively steep (45°, significant gravity backflow). In the preliminary screening stage, 5° is used as the initial scan step size, that is, the fluid performance is calculated sequentially at discrete angles such as α=0°, 5°, 10°, ..., 45°. This coarse-grained scan aims to quickly locate the approximate range of extreme values ​​of the comprehensive performance evaluation index F(α), avoiding wasting computational resources in invalid regions and improving optimization efficiency.

[0082] When the initial scan results indicate that the overall performance score reaches its peak or shows a clear inflection point within a certain angle range (e.g., between 15° and 25°), the fine-tuning stage begins. At this point, the step size within this range is reduced to 1°, meaning more densely packed angle values ​​are calculated, such as α = 15°, 16°, ..., 25°. By increasing the resolution, subtle changes in the performance curve can be captured more accurately, thereby identifying the optimal tilt angle α that maximizes the overall performance score F(α), ensuring the accuracy of the design parameters.

[0083] Meanwhile, to accurately simulate the splashing, two-phase flow, and backflow processes of lubricating oil under the agitation of a high-speed rotating sprocket, a high-quality mesh was created for the entire computational domain (including the main oil sump, oil reservoir, inlet and outlet channels, and the fluid region near the sprocket and chain surfaces). Due to the drastic changes in the free surface, turbulence, and boundary layer flow near the walls, the mesh quality directly determines the simulation accuracy. Therefore, a high-density mesh of approximately ten million pixels was used for discretization. Further local mesh refinement was applied at the sprocket and chain rotation interface, the free surface fluctuation region, and near the inclined bottom surface of the oil reservoir to capture the detailed features of high-speed jet impact, droplet breakup, and oil film flow. This high mesh density significantly reduces numerical discretization errors, ensuring that the transient solver can stably and realistically reflect the dynamic distribution and stress conditions of the lubricating oil at different tilt angles α, providing reliable data support for subsequent performance evaluation calculations.

[0084] Optionally, the optimal value of the tilt angle α can be calculated separately for different vehicle models. Based on the specific power parameters of the target vehicle (such as engine torque curve, transfer case ratio, sprocket tooth count, etc.) and environmental parameters, the boundary conditions for the simulation calculation are constructed. Specifically, for low-speed traction conditions, a low-speed, high-torque rotation state of the input shaft is set to simulate the extreme climbing scenario of the vehicle on low-traction surfaces such as mud and sand; for high-speed cruising conditions, a high-speed, low-load rotation state of the input shaft is set to simulate the stable driving scenario of the vehicle on paved roads.

[0085] Subsequently, a transient solver from Computational Fluid Dynamics (CFD) was used for multiphysics coupled simulation. This solver can handle time-varying fluid problems, capturing in real time the complex motion process of lubricating oil under high-speed agitation by sprockets and chains, including oil splashing, droplet breakup and coalescence, the impact process of oil jet entering the oil reservoir, and the backflow process under gravity. During the simulation, the system records two key physical quantities in real time:

[0086] Oil temperature change: The temperature field distribution of the lubricating oil during the entire circulation process is solved by the energy equation, especially the average temperature rise in the friction plate area and the main oil sump, thereby extracting the lubricating oil temperature rise value T under low-speed obstacle removal conditions. 升 (α).

[0087] Resistance torque: By monitoring the shear stress and pressure distribution on the surfaces of the sprocket and chain, the fluid resistance torque on the sprocket and chain assembly is calculated by integration, and compared with the resistance torque under the reference condition without an oil reservoir, to calculate the reduction in churning torque η under high-speed cruising conditions. 降 (α).

[0088] T corresponding to different tilt angles α 升 (α) and η 降 (α) Substitute into the pre-set comprehensive performance evaluation index formula In this process, the comprehensive score at each angle is calculated. A performance curve is plotted with the tilt angle α as the abscissa and the comprehensive performance score F(α) as the ordinate. This curve typically exhibits a single-peak characteristic, and the abscissa value corresponding to its peak point (highest point) is the optimal tilt angle α under the current vehicle model parameters and weight configuration. This process achieves a leap from qualitative design to quantitative optimization, ensuring a high degree of matching between the design parameters and the actual operating conditions of the vehicle.

[0089] Furthermore, to verify the engineering reliability of the simulation results, a physical experimental verification stage was initiated. First, based on the calculated optimal tilt angle α, a transfer case prototype with the bottom surface of the oil reservoir at this specific tilt angle was fabricated using precision casting or CNC machining techniques. This prototype must strictly conform to the geometric dimensions and surface roughness requirements of the simulation model.

[0090] Subsequently, the prototype was mounted on a dedicated transfer case performance test bench. The bench simulated the load and speed conditions of a real vehicle, applying low-speed obstacle avoidance and high-speed cruising conditions. Under low-speed conditions, a high-precision infrared thermometer or a temperature sensor embedded in the oil circuit was used to measure the temperature rise of the lubricating oil over a specific time period, and this was compared with the simulation-predicted T_rise (α). Under high-speed conditions, a high-precision torque sensor was used to measure the churning resistance torque of the sprocket chain, calculate the actual reduction in churning torque, and compare this with the simulation-predicted η_reduction (α). The relative deviation between the measured data and the simulation-predicted data was controlled within ±10%. If the deviation was within this range, it indicated that the established simulation model accurately reflected physical reality, and the optimal tilt angle α determined by the algorithm was reliable and feasible, and could be formally applied to the design of mass-produced vehicles. If the deviation exceeded the range, the simulation boundary conditions, mesh quality, or physical model assumptions needed to be checked, corrected, and iteratively optimized again until the simulation and experimental results highly matched. This closed-loop verification process ensured the consistency between the theoretical design's engineering feasibility and the expected actual performance.

[0091] According to another aspect of the present invention, a transfer case is provided, the transfer case having a transfer case lubrication system, the transfer case lubrication system being the transfer case lubrication system described above.

[0092] According to another specific embodiment of this application, a vehicle is also provided, the vehicle having a transfer case, the transfer case being the transfer case described above.

[0093] It should be further explained that the core principle of the transfer case lubrication system proposed in this invention lies in utilizing the difference in kinetic energy of oil splashed by rotating components (such as sprockets and chains) at different speeds, combined with the gravitational backflow effect of the inclined bottom surface, to achieve automatic, passive, and dynamic distribution of lubricating oil between the main oil sump and the oil reservoir. This physical mechanism is not only applicable to traditional four-wheel drive transfer cases, but its technical concept also has high versatility and scalability, and can be widely applied to other automotive transmission assemblies that use splash lubrication, mainly including electric drive systems and drive axle systems.

[0094] The application of the technical solution of this application has the following beneficial effects:

[0095] 1. This invention can increase the total fuel capacity of the transfer case and increase the heat capacity, so that the friction plates of the four-wheel drive system are less likely to overheat when getting out of trouble at low speed and high load, thus enhancing the four-wheel drive system's ability to get out of trouble.

[0096] 2. When the vehicle is traveling at high speed, the present invention automatically "pumps" the lubricating oil in the main oil sump and temporarily stores it in the auxiliary cavity using hydrodynamics at high speed, thereby reducing the liquid level in the main oil sump, reducing the amount of oil agitated by the transfer case working sprocket chain, slowing down the rise in transfer case oil temperature, improving the transmission efficiency of the four-wheel drive system, and reducing fuel consumption.

[0097] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0098] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0099] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A transfer case lubrication system, characterized in that, include: Transfer case (1), the transfer case (1) is provided with a main oil sump (2) for containing lubricating oil. A sprocket and chain assembly (3) is located inside the transfer case housing (1), and part of the sprocket and chain assembly (3) is disposed in the main oil sump (2). The sprocket and chain assembly (3) is used to agitate the lubricating oil during rotation. Oil storage cavity (4), the oil storage cavity (4) is located on the side of the sprocket and chain assembly (3) away from the main oil tank (2), and the oil storage cavity (4) is connected to the main oil tank (2); The bottom surface of the oil storage cavity (4) has a preset tilt angle α relative to the horizontal plane, and the opening of the oil storage cavity (4) faces the rotational tangent direction of the sprocket and chain assembly (3).

2. The transfer case lubrication system according to claim 1, characterized in that, The bottom surface of the oil storage cavity (4) is a circular arc surface, and the length of the oil storage cavity (4) is smaller than the length of the chain of the sprocket and chain assembly (3).

3. The transfer case lubrication system according to claim 1, characterized in that, The tilt angle α ranges from 0° to 45°.

4. The transfer case lubrication system according to claim 3, characterized in that, The oil storage cavity (4) is located above the main oil tank (2), and the vertical distance between the bottom of the oil storage cavity (4) and the liquid surface of the main oil tank (2) is 0mm~200mm.

5. The transfer case lubrication system according to claim 4, characterized in that, The oil storage cavity (4) forms an open channel (5) inside, which includes an oil inlet channel (51) and an oil return channel (52). The opening of the oil inlet channel (51) faces the rotational tangent of the sprocket and chain assembly (3) and is located at the oil inlet end of the oil storage cavity (4). The opening of the oil return channel (52) is located at the oil return end of the oil storage cavity (4) and is lower than the vertical projection position of the opening of the oil inlet channel (51) so as to utilize gravity to achieve natural return of lubricating oil.

6. The transfer case lubrication system according to claim 5, characterized in that, The oil inlet channel (51) and the oil return channel (52) are set independently, or the oil inlet channel (51) and the oil return channel (52) are an integrated connecting channel.

7. The transfer case lubrication system according to claim 1, characterized in that, The oil storage cavity (4) is integrally cast with the transfer case housing (1), or the oil storage cavity (4) is a separate component independent of the transfer case housing (1), and the inner wall surface of the oil storage cavity (4) is detachably connected to the transfer case housing (1).

8. The transfer case lubrication system according to claim 1, characterized in that, The transfer case lubrication system further includes a variable fluid level auxiliary module, which includes a level sensor, an electronic oil pump, and a control unit installed in the main oil sump (2). The level sensor is used to monitor the lubricating oil level in real time and transmit the signal to the control unit. The control unit controls the electronic oil pump to actively pump the lubricating oil between the oil storage chamber (4) and the main oil sump (2) according to the vehicle operating conditions and the level signal, so as to achieve fine adjustment of the amount of lubricating oil in the main oil sump (2).

9. A method for determining the tilt angle α of a transfer case lubrication system as described in any one of claims 1-8, characterized in that, include, Establish a three-dimensional model of the transfer case lubrication system; A comprehensive performance evaluation index is generated based on the lubricating oil temperature rise under low-speed traction conditions and the reduction in churning torque under high-speed cruising conditions. Based on the comprehensive performance evaluation index, the initial tilt angle is iteratively optimized to determine the optimal value as the target tilt angle α.

10. A transfer case, characterized in that, The transfer case has a transfer case lubrication system, which is the transfer case lubrication system according to any one of claims 1-8.

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