Mode-switching-based wide and efficient hmcvt multi-working-condition transmission system and method

Abstract

The application provides a wide and efficient HMCVT multi-working condition transmission system and method based on mode switching, and belongs to the technical field of transmission design. The application discloses a wide and efficient HMCVT multi-working condition transmission system and method based on mode switching, and belongs to the technical field of transmission design. The middle shaft and the input shaft of the shaft assembly are fixed through the first lock and the second lock in the lock assembly, and a gear transmission network is constructed through the planetary gear assembly. The switching between the input coupling mode, the output coupling mode and the pure mechanical mode is realized by selectively connecting and disconnecting the multiple clutches in the clutch assembly and the multiple locks in the lock assembly. The application can dynamically adjust the coupling mode according to the working condition, cut off the power circulation path in structure, and simultaneously consider multiple complex working conditions such as low-speed heavy load and high-speed light load, so that the efficient transmission of the HMCVT is realized.

Description

Technical Field

[0001] This invention belongs to the field of transmission design technology, and particularly relates to a wide-range, high-efficiency HMCVT multi-condition transmission system and method based on mode switching. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Hydraulic-mechanical continuously variable transmissions (HMCVTs) combine the advantages of continuously variable speed regulation of hydraulic transmission with the high efficiency of mechanical transmission, and are now widely used in tractors, construction machinery, and other fields. Traditional HMCVTs typically employ an input-split or output-split structure, achieving continuously variable speed through continuous speed adjustment via a hydraulic unit. However, this conventional structure has significant limitations: its efficient operating range is relatively narrow, making it difficult to simultaneously meet the demands of various complex working conditions such as heavy-duty operations and highway transportation.

[0004] In practical applications of HMCVT, power cycling is one of the key factors affecting transmission efficiency. Power cycling refers to the phenomenon where, when the system operates within a specific speed ratio range, some power is not transmitted to the output but instead circulates internally between the hydraulic and mechanical circuits. This not only results in wasted power but also places additional loads on hydraulic components, generating significant heat. While existing technologies attempt to broaden the speed range through multi-stage HMCVTs, power cycling remains difficult to avoid at specific speed ratio points within a stage, especially when the hydraulic power flow direction reverses. In severe cases, it can even lead to system overheating and a sharp drop in efficiency.

[0005] To mitigate power cycling, some existing designs employ complex hydraulic circuit controls or add additional brakes to limit power flow. However, this often makes the control strategy extremely complex, placing higher demands on the response speed and reliability of hydraulic components. Furthermore, in single-mode HMCVT, the hydraulic system still needs to operate continuously under high-speed, light-load conditions, and its inherent losses result in transmission efficiency far lower than that of purely mechanical transmission, leading to energy waste. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a wide-range and high-efficiency HMCVT multi-condition transmission system and method based on mode switching. It can dynamically adjust the coupling mode according to the operating conditions and cut off the power circulation path from the structure, thereby simultaneously taking into account a variety of complex operating conditions such as low-speed heavy load and high-speed light load, and realizing the high-efficiency transmission of HMCVT.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching.

[0008] The wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching includes: engine, shaft assembly, planetary gear assembly, clutch assembly, and lock-up assembly; The engine achieves power input, transmission, and output through the input shaft, intermediate shaft, and output shaft in the shaft assembly, respectively. The intermediate shaft and the input shaft are fixed by the first locker and the second locker in the locking assembly, respectively, and a gear transmission network is constructed by the planetary gear assembly; The system, based on the gear transmission network, achieves switching between input coupling mode, output coupling mode, and pure mechanical mode by selectively switching multiple clutches in the clutch assembly and multiple lockers in the locker assembly, in order to adapt to different working conditions.

[0009] Furthermore, the first gear in the planetary gear assembly is fixed to the input shaft, and the input shaft is divided into two sections by a shaft head clutch; the section closer to the output shaft is connected to the planet carrier on the second planetary gear mechanism in the planetary gear assembly; at the same time, the planet carrier is connected to the gear ring on the third planetary gear mechanism in the planetary gear assembly.

[0010] Furthermore, the intermediate shaft is connected to the planet carrier on the first planetary gear mechanism in the planetary gear assembly; at the same time, the second clutch and the third clutch in the clutch assembly are respectively connected to the gear ring of the second planetary gear mechanism and the planet carrier of the third planetary gear mechanism.

[0011] Furthermore, the on / off states of the multiple clutches in the clutch assembly corresponding to the input coupling mode and the multiple locks in the lock assembly are as follows: The first locking device is engaged, and the second locking device is disengaged; The first clutch engages, the second clutch disengages, and the third clutch disengages. The fourth clutch selectively engages according to a preset speed requirement threshold. When the transmission speed is lower than the speed requirement threshold, the fourth clutch engages to the right; otherwise, the fourth clutch engages to the left.

[0012] Furthermore, in the input coupling mode, the power is split from the input shaft through a gear transmission network into a first mechanical path and a first hydraulic path. The power of the first hydraulic path can be selectively combined with the second planetary gear mechanism or the third planetary gear mechanism depending on the engagement state of the fourth clutch, and finally the power is delivered to the output shaft.

[0013] Furthermore, the on / off states of the multiple clutches in the clutch assembly corresponding to the output coupling mode and the multiple locks in the lock assembly are as follows: The first locking device is disengaged, and the second locking device is engaged; The first clutch is disengaged, the second clutch is engaged, the third clutch is disengaged, and the fourth clutch is engaged on the right.

[0014] Furthermore, in the output coupling mode, the power is split from the input shaft into a second mechanical path and a second hydraulic path via a first planetary gear mechanism. The power from the second mechanical path is then fed into the output shaft via the second planetary gear mechanism, and the power from the second hydraulic path is fed into the third planetary gear mechanism.

[0015] Furthermore, the on / off states of the multiple clutches in the clutch assembly and the multiple locks in the lock assembly corresponding to the purely mechanical mode are as follows: The first locking device is engaged, and the second locking device is disengaged; The first clutch engages, the second clutch disengages, the third clutch engages, and the fourth clutch disengages.

[0016] Furthermore, in the purely mechanical mode, all the engine's power is directly transmitted to the output shaft via a third mechanical path.

[0017] The second aspect of the present invention provides a wide and efficient HMCVT multi-condition transmission method based on mode switching, for use in the transmission system as described in the first aspect.

[0018] A wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching includes: Obtain vehicle operating status information, including vehicle speed and load torque; The current operating condition of the vehicle is determined based on the status information; When the system is determined to be in a low-speed, heavy-load condition, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to input coupling mode. When the system is determined to be operating under high-speed light load conditions, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to output coupling mode. In this mode, the engine power is split by the first planetary gear mechanism and then merged at the output shaft through the second planetary gear mechanism and the third planetary gear mechanism respectively. When the driving condition is determined to be stable, the first locking device, the second locking device, and the first to fourth clutches are controlled to work together to switch the system to a purely mechanical mode, so that all engine power is transmitted to the output shaft through a mechanical path.

[0019] The above one or more technical solutions have the following beneficial effects: This invention, through a structured design with three modes—input coupling, output coupling, and pure mechanical—structurally expands the efficient operating range of the transmission system, solving the problem that existing HMCVTs struggle to handle both heavy-duty operations and high-speed transportation. The input coupling mode is used at low speeds, while the output coupling mode switches to high speeds; these two power-split modes meet the continuously variable transmission requirements under different operating conditions. During stable driving, the pure mechanical mode is activated to effectively eliminate the inherent losses of hydraulic transmission, achieving transmission efficiency comparable to that of pure mechanical transmissions. The flexible switching between these three modes allows a single transmission system to cover all operating conditions, from heavy-duty field work to highway transportation.

[0020] This invention eliminates the power circulation path at the structural level, solving the efficiency reduction problem caused by power circulation in existing technologies. In input coupling mode, the intermediate shaft and the planetary carrier of the first planetary gear mechanism are fixed by a first locking device, causing the flow splitting mechanism to degenerate into a gear pair. In output coupling mode, the planetary carrier and gear ring are locked by a second locking device, similarly causing the flow merging mechanism to degenerate into a gear pair. In this way, the hydraulic power circulation phenomenon can be avoided as much as possible by switching between different modes within the same transmission structure. This solution does not rely on complex sensor feedback or hydraulic dynamic adjustment, resulting in higher reliability and effectively reducing the heat generation and efficiency loss caused by power circulation. In addition, in pure mechanical mode, the hydraulic pump and hydraulic motor completely stop working, not only improving the transmission efficiency to a level close to that of pure mechanical transmission, but also significantly reducing the hydraulic system's operating time, reducing component wear and heat load, and extending service life. At the same time, switching between the three modes can be achieved simply by combining the on and off states of a few clutches and locking devices. The control logic is simple, requiring no complex hydraulic circuit adjustment or electronic control algorithm support, reducing the requirements for controllers and hydraulic components, and making it easier to implement and promote in engineering.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, 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 improper limitation of the invention.

[0023] Figure 1 This is an architecture diagram of the wide-range, high-efficiency HMCVT multi-condition transmission system based on mode switching in Embodiment 1 of the present invention.

[0024] Figure 2 This is a flowchart of the wide-range, high-efficiency HMCVT multi-condition transmission method based on mode switching in Embodiment 1 of the present invention.

[0025] In the diagram: 1. First planetary gear mechanism; 2. Second planetary gear mechanism; 3. Third planetary gear mechanism; 4. First locking device; 5. Second locking device; 6. First clutch; 7. Second clutch; 8. Third clutch; 9. Fourth clutch; 10. First gear ring; 11. Second gear ring; 12. Third gear ring; 13. First gear; 14. Second gear; 15. Third gear; 16. Fourth gear; 17. Fifth gear; 18. First sun gear; 19. Second sun gear; 20. Third sun gear; 21. First planet carrier; 22. Second planet carrier; 23. Third planet carrier. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0028] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] Example 1 This embodiment discloses a wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching.

[0030] The wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching includes: engine, shaft assembly, planetary gear assembly, clutch assembly, and lock-up assembly; The engine achieves power input, transmission, and output through the input shaft, intermediate shaft, and output shaft in the shaft assembly, respectively. The intermediate shaft and the input shaft are fixed by the first locker and the second locker in the locking assembly, respectively, and a gear transmission network is constructed by the planetary gear assembly; The system, based on the gear transmission network, achieves switching between input coupling mode, output coupling mode, and pure mechanical mode by selectively switching multiple clutches in the clutch assembly and multiple lockers in the locker assembly, in order to adapt to different working conditions.

[0031] Based on the above structured design, this invention can dynamically adjust the coupling mode according to operating conditions and structurally cut off the power circulation path, thereby simultaneously accommodating various complex operating conditions such as low-speed heavy load and high-speed light load, achieving efficient transmission of HMCVT. To facilitate understanding of the technical solution of this invention, the specific implementation methods are further explained and described below.

[0032] The present invention provides a wide-range, high-efficiency HMCVT multi-condition transmission system based on mode switching, comprising: an engine, a shaft assembly, a planetary gear assembly, a clutch assembly, and a lock-up assembly; wherein, the shaft assembly includes an input shaft, an intermediate shaft, and an output shaft; the planetary gear assembly includes a first planetary gear mechanism 1, a second planetary gear mechanism 2, and a third planetary gear mechanism 3; the clutch assembly includes a first clutch 6, a second clutch 7, a third clutch 8, and a fourth clutch 9, wherein the first clutch 6 is a shaft head clutch; and the lock-up assembly includes a first lock-up device 4 and a second lock-up device 5.

[0033] Furthermore, the wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching also includes: a hydraulic pump and a hydraulic motor.

[0034] like Figure 1 As shown, the engine inputs power through the input shaft, on which the first gear 13 is fixed. The first clutch 6 (i.e., the shaft head clutch) divides the input shaft into two parts. The second half of the input shaft can be fixed by the second locking device 5. The second half of the input shaft is connected to the second planetary carrier 22 of the second planetary gear mechanism 2. The second planetary carrier 22 is directly connected to the third gear ring 12 of the third planetary gear mechanism 3.

[0035] The intermediate shaft has a first locking device 4 to fix the intermediate shaft. The intermediate shaft is also connected to the first planetary carrier 21 of the first planetary gear mechanism 1. In addition, the first ring gear 10 and the first gear 13 of the first planetary gear mechanism are connected, the first sun gear 18 and the second gear 14 are connected, the second clutch 7 on the intermediate shaft is connected to the second ring gear 11 of the second planetary gear mechanism 2, and the third clutch 8 is connected to the third planetary carrier 23 of the third planetary gear mechanism 3.

[0036] In the hydraulic path, the second gear 14 is connected to the hydraulic pump, the hydraulic pump is connected to the hydraulic motor through the oil supply line, the hydraulic motor is connected to the fourth clutch 9, one side of the fourth clutch 9 is connected to the third gear 15, and the other side is connected to the fourth gear 16. The third gear 15 can be connected to the second clutch 7, and the fourth gear 16 can be connected to the third clutch 8.

[0037] The second sun gear 19 and the third sun gear 20 on the second planetary gear mechanism 2 and the third planetary gear mechanism 3 are fixed on the output shaft. At the same time, the output shaft is connected to the fifth gear 17, which serves as a gear for outputting power outward.

[0038] Based on the above-mentioned structured design, and according to the different operating conditions of hybrid vehicles, this invention sets three working modes for the HMCVT transmission system: input coupling mode, output coupling mode, and pure mechanical mode.

[0039] The input coupling mode in this invention is activated when the vehicle is starting at low speed (the starting speed of a conventional tractor is 0-10 km / h), and the output coupling mode is activated when the vehicle is at high speed (when the speed is greater than 10 km / h, it is considered to have reached the high speed of a tractor). These two modes are designed to meet the continuously variable transmission (CVT) requirements of the vehicle, such as during vehicle starting or road driving. The pure mechanical mode is activated when the vehicle is in a stable operating condition with minimal speed fluctuations (e.g., when a tractor is working in a flat field). This mode does not have speed requirements; it can be used regardless of whether the vehicle speed is low or high, as long as the movement is smooth and there is basically no need for gear shifting. In this way, the pure mechanical mode can utilize its highest transmission efficiency under stable operating conditions. This invention, through mode switching, ensures that the system always operates within its respective non-cyclic range.

[0040] The on / off states of multiple clutches in the clutch assembly and multiple lockers in the locker assembly under each operating mode are shown in Table 1.

[0041] Table 1. On / off status of clutch and lock under various operating modes

[0042] 1) Input coupling mode.

[0043] As shown in Table 1, in input coupling mode, the second clutch 7 and the third clutch 8 need to be disengaged, the first clutch 6 is engaged, and a fourth clutch 9 acts as a special clutch that switches according to the situation. The second lock-up device 5 is disengaged, while the first lock-up device 4 is engaged. Specifically, the fourth clutch 9 is a bidirectional clutch, meaning it has two engagement modes. In this invention, left engagement means the fourth clutch 9 engages with the third gear 15, while right engagement means it engages with the fourth gear 16. This clutch is mainly designed to provide a wider transmission ratio range for the entire transmission mechanism. According to the planetary gear mechanism characteristic formula, right engagement is used when the initial starting speed requirement is low (i.e., the transmission speed is lower than the preset speed requirement threshold), and left engagement is used when the vehicle speed is relatively higher after a period of starting (i.e., the transmission speed is equal to or greater than the preset speed requirement threshold). This allows for a wider range of vehicle speeds to be matched within the limited gear pair transmission ratio design range. It should be noted that the speed requirement threshold can be the 10 km / h mentioned above, or it can be adjusted according to the actual situation. Therefore, this embodiment does not specifically limit the value of the speed requirement threshold.

[0044] This operating mode keeps the first planetary carrier 21 and the entire intermediate shaft of the first planetary gear mechanism stationary. Only the ring gear and sun gear of the first planetary gear mechanism can transmit power; it no longer has the ability to split power. Functionally, it is equivalent to a gear pair, whose role is to transmit power from the engine to the hydraulic pump, which in turn drives the hydraulic motor. The power from the hydraulic motor is then transmitted through the second clutch 7 or the third clutch 8 to the second or third planetary gear mechanism connected to the engine input shaft. Here, the power from the hydraulic path merges with another portion of the power from the engine input shaft (i.e., the mechanical path power flow) in the planetary gear mechanism, and finally performs work through the output shaft. The input coupling mode is an arrangement that utilizes both gear pairs for power splitting and planetary gear sets for power merging.

[0045] As mentioned above, the power from the hydraulic path and the mechanical path can be combined through either the second planetary gear mechanism or the third planetary gear mechanism. This function is achieved by the fourth clutch 9, which can engage in two ways: one is to engage the third gear 15 on the left, so that the power output from the hydraulic motor is transmitted to the third gear 15 and then acts on the second planetary gear mechanism; the other is to engage the fourth gear 16 on the right, so that the fourth gear 16 on the right transmits power and acts on the third planetary gear mechanism.

[0046] The difference between different planetary gear systems lies in the different functions of the ring gear and the planet carrier. If the second planetary gear mechanism is used for power confluence, the power from the hydraulic path is transmitted to the second ring gear 11 of the second planetary gear mechanism via the second clutch 7, while the power from the mechanical path is transmitted to the second planet carrier 22. After confluence, the power is output outward through the second sun gear 19 of the second planetary gear mechanism. If the third planetary gear mechanism is used for power confluence, the power from the hydraulic path is transmitted to the third planet carrier 23 of the third planetary gear mechanism via the third clutch 8, while the power from the mechanical path is transmitted to the third ring gear 12. After confluence, the power is output outward through the third sun gear 20 of the third planetary gear mechanism. This differs from the existing input-coupled HMCVT structure. This dual planetary gear mechanism allows for an additional confluence method for the two power flows. Different confluence methods can result in different transmission ratios, providing a wider range of adjustments for the HMCVT to meet vehicle speed requirements and mitigate power cycling phenomena.

[0047] 2) Output coupling mode.

[0048] As shown in Table 1, in the output coupling mode, the first clutch 6 and the third clutch 8 are disengaged, the second clutch 7 is engaged, the fourth clutch 9 is engaged, the first lock is disengaged, and the second lock is engaged.

[0049] In this configuration, all three components of the first planetary gear mechanism—the first ring gear 10, the first sun gear 18, and the first planet carrier 21—can move freely. Furthermore, the planet carrier connects to and drives the intermediate shaft, making the first planetary gear mechanism a complete power distribution mechanism. The first ring gear 10 receives power from the engine and distributes it into two parts: one part is transmitted to the hydraulic pump via the first sun gear 18, driving the hydraulic motor (hydraulic path); the other part drives the intermediate shaft via the first planet carrier 21 (mechanical path). The intermediate shaft then transmits the mechanical path portion of the power to the second ring gear 11 of the second planetary gear mechanism via the engaged second clutch 7. At this point, the second planet carrier 22 of the second planetary gear mechanism is fixed by the second locking device. Therefore, the power received by the second ring gear 11 can only be transmitted to the second sun gear 19 via the planet gears, which then drives the output shaft to rotate. The entire second planetary gear mechanism is now equivalent to a gear pair. The power in the hydraulic path section is output from the hydraulic motor via the fourth clutch 9 of the right-hand engagement fourth gear 16 to the third clutch 8, and then transmitted to the third planetary carrier 23 of the third planetary gear mechanism through the disengaged third clutch 8. Similarly, since the ring gear of the third planetary gear mechanism has been locked by the second locking device, the power received on the planetary carrier can only be transmitted to the third sun gear 20 through the planet gears, and then to the output shaft. The entire third planetary gear mechanism is equivalent to a gear pair.

[0050] In summary, the output coupling mode uses the first planetary gear mechanism as a diverter, and then fixes the planet carrier of the second planetary gear mechanism and the gear ring of the third planetary gear mechanism so that each gear system can only function as a gear pair, receiving power from the mechanical path and the hydraulic path respectively, and then outputting it through the sun gear. Since the sun gears of the two gear systems are connected to the same output shaft, the power of the two gear systems is combined through the common output shaft. At this time, the two gear systems act as a combined flow mechanism, but its combined flow method is the same as that of a gear pair. This input coupling mode is different.

[0051] 3) Pure mechanical mode.

[0052] As shown in Table 1, the pure mechanical mode refers to a mode in which the hydraulic system components stop working, the first locking device is engaged, the second locking device is disengaged, the second and fourth clutches are disengaged, and the first and third clutches are engaged. In this case, the hydraulic pump and hydraulic motor stop working, and the engine power is not transmitted to the hydraulic path; instead, it is all output to the outside through the mechanical path via the engine input shaft. The power from the engine input shaft is transmitted from the second planetary carrier 22 of the second planetary gear mechanism to the third ring gear 12 of the third planetary gear mechanism. Among the three components of the third planetary gear mechanism, the third ring gear 12 receives power from the engine, and the third planetary carrier 23 is connected to the third clutch 8. However, the gear containing the third clutch 8 is fixed due to the locking of the first locking device, and consequently, the planetary carrier is also fixed. Therefore, the power on the ring gear can be directly transmitted to the third sun gear 20 for external output through the planetary gears.

[0053] The pure mechanical mode is primarily suitable for vehicles using HMCVT that do not require frequent speed changes under certain operating conditions, thus eliminating the need for continuously variable transmission (CVT) functionality, such as agricultural tractors during operation. In such cases, to maximize transmission efficiency, hydraulic transmission is not actually necessary, as the primary function of the hydraulic transmission in HMCVT is to achieve CVT through changes in displacement ratio. However, this does indeed reduce overall transmission efficiency. Therefore, an additional pure mechanical mode was designed specifically for these operating conditions.

[0054] Based on the above design, the present invention achieves the following technical breakthroughs: 1) This invention enables the transmission system to select a more suitable power distribution path for different speed ratio ranges and load conditions by switching between two HMCVT structures: input coupling and output coupling. The efficiency of input coupling and output coupling varies under different operating conditions. Studies have shown that input coupling is more advantageous under small displacement conditions, while output coupling is more efficient over larger displacements or wider speed ratio ranges. Based on this, this invention can reduce the circulating power under unfavorable operating conditions through mode switching.

[0055] 2) The new structure can expand the high-efficiency operating range of HMCVT and improve the problem of uneven efficiency distribution in single coupling mode. Since the power flow modes of input coupling and output coupling are different, after switching the coupling mode, the system can adjust the operating point to a structure with lower cyclic power, thereby reducing the ineffective power flow in hydraulic and gear branches and improving the system's adaptability under complex working conditions.

[0056] 3) This invention also helps to improve the stability and reliability of the transmission system. After the power cycle is reduced, the return power and additional losses inside the system are reduced simultaneously, which can reduce the workload of hydraulic components and gear pairs, improve dynamic response performance, and thus reduce the risk of efficiency decay and component wear caused by overload cycles.

[0057] Example 2 This embodiment discloses a wide-range, high-efficiency HMCVT multi-condition drive method based on mode switching.

[0058] like Figure 2 As shown, the wide-range, high-efficiency HMCVT multi-condition drive method based on mode switching includes: Obtain vehicle operating status information, including vehicle speed and load torque; The current operating condition of the vehicle is determined based on the status information; When the system is determined to be in a low-speed, heavy-load condition, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to input coupling mode. When the system is determined to be operating under high-speed light load conditions, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to output coupling mode. In this mode, the engine power is split by the first planetary gear mechanism and then merged at the output shaft through the second planetary gear mechanism and the third planetary gear mechanism respectively. When the driving condition is determined to be stable, the first locking device, the second locking device, and the first to fourth clutches are controlled to work together to switch the system to a purely mechanical mode, so that all engine power is transmitted to the output shaft through a mechanical path.

[0059] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching, characterized in that, include: Engine, shaft assembly, planetary gear assembly, clutch assembly, lock-up assembly, hydraulic pump and hydraulic motor; The shaft assembly includes an input shaft, an intermediate shaft, and an output shaft; the planetary gear assembly includes a first planetary gear mechanism, a second planetary gear mechanism, and a third planetary gear mechanism; the clutch assembly includes a first clutch, a second clutch, a third clutch, and a fourth clutch, wherein the first clutch is a shaft head clutch; and the locking device assembly includes a first locking device and a second locking device. The engine realizes the input, transmission and output of power through the input shaft, intermediate shaft and output shaft in the shaft assembly respectively. Specifically, the engine inputs power through the input shaft. A first gear is fixed on the input shaft. The first clutch divides the input shaft into two parts. The rear half of the input shaft is fixed by a second locker. The rear half of the input shaft is connected to the second planetary carrier of the second planetary gear mechanism. The second planetary carrier is directly connected to the third gear ring of the third planetary gear mechanism. The intermediate shaft and the input shaft are fixed by the first locker and the second locker in the locking assembly, respectively, and a gear transmission network is constructed by the planetary gear assembly. Specifically, the intermediate shaft is fixed by the first locker. The intermediate shaft is also connected to the first planetary carrier of the first planetary gear mechanism. In addition, the first ring gear and the first gear of the first planetary gear mechanism are connected, the first sun gear and the second gear are connected, the second clutch on the intermediate shaft is connected to the second ring gear of the second planetary gear mechanism, and the third clutch is connected to the third planetary carrier of the third planetary gear mechanism. The system is equipped with three operating modes: input coupling mode, output coupling mode, and pure mechanical mode. Based on the gear transmission network, the system switches between these modes by selectively switching on and off multiple clutches in the clutch assembly and multiple lockers in the locker assembly to adapt to different working conditions. Specifically, in the hydraulic path, the second gear is connected to a hydraulic pump, which is connected to a hydraulic motor via an oil pipeline. The hydraulic motor is connected to a fourth clutch. One side of the fourth clutch is connected to a third gear, and the other side is connected to a fourth gear. The third gear is connected to the second clutch, and the fourth gear is connected to the third clutch. The second sun gear and the third sun gear on the second and third planetary gear mechanisms are fixed on the output shaft. At the same time, the output shaft is connected to a fifth gear, which serves as the gear for outputting power.

2. The wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching as described in claim 1, characterized in that, The on / off states of the multiple clutches in the clutch assembly and the multiple locks in the lock assembly corresponding to the input coupling mode are as follows: The first locking device is engaged, and the second locking device is disengaged; The first clutch engages, the second clutch disengages, and the third clutch disengages. The fourth clutch selectively engages according to a preset speed requirement threshold. When the transmission speed is lower than the speed requirement threshold, the fourth clutch engages to the right; otherwise, the fourth clutch engages to the left.

3. The wide-range, high-efficiency HMCVT multi-condition transmission system based on mode switching as described in claim 2, characterized in that, In the input coupling mode, power is split from the input shaft into a first mechanical path and a first hydraulic path via a gear transmission network. The power in the first hydraulic path can be selectively combined with the second planetary gear mechanism or the third planetary gear mechanism depending on the engagement state of the fourth clutch, and finally the power is delivered to the output shaft.

4. The wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching as described in claim 1, characterized in that, The on / off states of the multiple clutches in the clutch assembly and the multiple locks in the lock assembly corresponding to the output coupling mode are as follows: The first locking device is disengaged, and the second locking device is engaged; The first clutch is disengaged, the second clutch is engaged, the third clutch is disengaged, and the fourth clutch is engaged on the right.

5. The wide-range, high-efficiency HMCVT multi-condition transmission system based on mode switching as described in claim 4, characterized in that, In the output coupling mode, the power is split from the input shaft into a second mechanical path and a second hydraulic path via a first planetary gear mechanism. The power from the second mechanical path is then fed into the output shaft via the second planetary gear mechanism, and the power from the second hydraulic path is fed into the third planetary gear mechanism.

6. The wide-range, high-efficiency HMCVT multi-condition drive system based on mode switching as described in claim 1, characterized in that, The on / off states of the multiple clutches in the clutch assembly and the multiple locks in the lock assembly corresponding to the pure mechanical mode are as follows: The first locking device is engaged, and the second locking device is disengaged; The first clutch engages, the second clutch disengages, the third clutch engages, and the fourth clutch disengages.

7. The wide-range, high-efficiency HMCVT multi-condition transmission system based on mode switching as described in claim 6, characterized in that, In the pure mechanical mode, all the power of the engine is directly transmitted to the output shaft via the third mechanical path.

8. A wide-range, high-efficiency HMCVT multi-condition transmission method based on mode switching, used in the transmission system as described in any one of claims 1-7, characterized in that, include: Obtain vehicle operating status information, including vehicle speed and load torque; The current operating condition of the vehicle is determined based on the status information; When the system is determined to be in a low-speed, heavy-load condition, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to input coupling mode. When the system is determined to be operating under high-speed light load conditions, the first lock-up device, the second lock-up device, and the first to fourth clutches are controlled to work together to switch the system to output coupling mode. In this mode, the engine power is split by the first planetary gear mechanism and then merged at the output shaft through the second planetary gear mechanism and the third planetary gear mechanism respectively. When the driving condition is determined to be stable, the first locking device, the second locking device, and the first to fourth clutches are controlled to work together to switch the system to a purely mechanical mode, so that all engine power is transmitted to the output shaft through a mechanical path.

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