Dual-mode transmission for electric vehicle and shifting method

Abstract

The application relates to the technical field of gearboxes, and provides a dual-mode gearbox for an electric vehicle and a gear shifting method. The dual-mode gearbox for the electric vehicle comprises a hydraulic torque converter with a lock-up clutch, a planetary gear mechanism, a speed reduction mechanism and a differential. The hydraulic torque converter further comprises an input shaft, a pump wheel, a turbine and an output shaft. The planetary gear mechanism comprises a sun gear, a large gear ring, a planetary gear set and a planet carrier. A driving motor is connected with the pump wheel through the input shaft. The pump wheel and the turbine are connected through fluid transmission and can be locked or unlocked through the lock-up clutch. The pump wheel is in transmission connection with the sun gear, and the turbine is in transmission connection with the large gear ring. The large gear ring and the sun gear are in transmission connection with the planet carrier through the planetary gear set. The planet carrier is connected with the output shaft. The output shaft is connected with the speed reduction mechanism and outputs power to wheels through the differential. The gearbox prolongs the service life of the motor and the clutch plate, improves the starting acceleration capacity of the electric vehicle, and is higher in vehicle operation reliability and stronger in power.

Description

Technical Field

[0001] This application belongs to the field of transmission technology, and more specifically, relates to a dual-mode transmission for electric vehicles and a transmission method thereof. Background Technology

[0002] Developing energy-saving and new energy vehicles has become an inevitable choice for my country's energy strategy. The current focus is on promoting the industrialization of pure electric vehicles and plug-in hybrid electric vehicles and improving the overall technological level of my country's automotive industry.

[0003] Currently, there are several main transmission schemes for electric vehicles. Scheme one is a fixed reduction ratio; scheme two is a two-speed transmission; and scheme three is to use the transmission of a traditional gasoline-powered vehicle. Because electric motors have a wide high-efficiency range, traditional gasoline-powered vehicle transmissions typically have four to seven gears, making their use in pure electric vehicles seem like overkill. While a fixed reduction ratio simplifies the transmission system, it results in poor acceleration and hill-climbing performance. Therefore, some have proposed a two-speed transmission scheme: a large reduction ratio for low-speed driving to achieve better starting performance, and a small reduction ratio for high-speed driving to meet the maximum speed requirements.

[0004] For example, patent document CN101780768A discloses a two-speed automatic transmission for electric vehicles. This electric vehicle transmission includes an input shaft, an intermediate shaft, an output shaft, a clutch, a brake, a planetary gear mechanism, and a differential. The sun gear and planet carrier of the planetary gear mechanism are respectively connected to the input shaft and the intermediate shaft. The clutch and brake are detachably connected to the internal ring gear of the planetary gear mechanism. The intermediate shaft is connected to the output shaft, and the output shaft is connected to the differential. Power is transmitted to the wheels through the differential, driving the vehicle. This transmission cleverly changes gears through a single planetary gear mechanism, resulting in a simple structure. This transmission reduces the requirements of the electric motor in electric vehicles to a certain extent, increases the time the drive motor operates in its high-efficiency range, and improves the driving range.

[0005] The main shortcomings of this electric vehicle transmission are as follows: First, the large changes in motor rotor speed and moment of inertia during gear shifts lead to significant wear on the friction plates of the brakes and clutches. Second, the motor operates in a stalled state during start-up, which can easily cause it to burn out. Therefore, the market urgently needs a simple electric vehicle-specific transmission that can address these shortcomings. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this application is to provide a high-performance, highly reliable dual-mode transmission for electric vehicles.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: A dual-mode transmission for electric vehicles is provided, comprising: a controller, a hydraulic torque converter with a lock-up clutch, a planetary gear mechanism, a reduction mechanism, and a differential. The controller controls the locking / unlocking of the lock-up clutch. The hydraulic torque converter further comprises an input shaft, a pump wheel, a turbine, and an output shaft. The planetary gear mechanism comprises a sun gear, a large ring gear, a planetary gear set, and a planet carrier. One end of the input shaft is connected to a drive motor, and the other end is connected to the pump wheel. The pump wheel and the turbine are driven together and locked or unlocked by the lock-up clutch. The pump wheel is driven together with the sun gear. The turbine is driven together with the large ring gear. The large ring gear and the sun gear are driven together with the planetary gear set and the planet carrier. The planet carrier is connected to the output shaft. The output shaft is connected to the reduction mechanism and outputs power to the wheels via the differential.

[0008] In one embodiment, the pump wheel is connected to the sun gear via a pump wheel bushing.

[0009] In one embodiment, the turbine is driven to the large gear ring via a turbine shaft.

[0010] In one embodiment, the first transmission mode of the transmission is a hydraulic torque converter transmission mode. The lock-up clutch unlocks the pump wheel and the turbine. The torque of the drive motor is input from the input shaft to the pump wheel and then splits into two parts. One part is transmitted to the sun gear through the pump wheel bushing, and the other part is transmitted from the turbine through the turbine shaft to the large ring gear after hydraulic torque converter transmission. The sun gear and the large ring gear transmit the obtained torque to the planetary gear set and then to the output shaft through the planet carrier. The output shaft drives the vehicle through the reduction mechanism and the differential, realizing the reduction transmission.

[0011] In one embodiment, the second transmission mode of the transmission is a direct mechanical transmission mode, in which the lock-up clutch locks the pump wheel and the turbine together, and also locks the sun gear and the large ring gear together. The planetary carrier rotates at the same speed as the sun gear and the large ring gear, so that the input shaft, pump wheel, turbine, sun gear, large ring gear, planetary carrier and output shaft all rotate at the same speed, and the torque of the drive motor is transmitted from the input shaft to the output shaft at a constant speed of 1:1.

[0012] In one embodiment, the hydraulic torque converter is powered by an oil pump driven by an oil pump motor, which is electrically connected to the controller.

[0013] In one embodiment, a damping spring is provided on the damping disc connected to the turbine.

[0014] Another objective of this application is to provide a gear shifting method based on the above-mentioned dual-mode transmission for electric vehicles, characterized by comprising the following steps:

[0015] S1. The controller collects accelerator pedal signals, vehicle speed, drive motor speed, and drive motor temperature parameters. First, it determines whether the vehicle is traveling at low speed. If it is traveling at medium to high speed, it controls the lock-up clutch to lock the torque converter, and the transmission is in direct mechanical transmission mode. If it is traveling at low speed, it continues to determine whether a large torque demand is required. If no large torque demand is required, it controls the lock-up clutch to lock the torque converter, and the transmission is in direct mechanical transmission mode. If a large torque demand is required, it controls the lock-up clutch to unlock the torque converter, and the transmission is in torque converter transmission mode.

[0016] S2. The controller determines whether the vehicle is in a long-term low-speed climbing condition based on the collected signal data such as vehicle speed, drive motor speed, drive motor torque, and drive motor temperature. If it is in a long-term low-speed climbing condition, the temperature rise of the drive motor will be large. At this time, the controller controls the lock-up clutch to unlock the hydraulic torque converter. After the hydraulic torque converter is unlocked, the drive motor works at a higher speed, the drive motor efficiency is higher, and the temperature rise is reduced. At the same time, the hydraulic torque converter works in hydraulic torque converter transmission mode, which has the function of deceleration and torque increase, and the motor torque is improved, which is more suitable for climbing.

[0017] S3. Except for low-speed, high-torque demand conditions and excessive motor temperature rise, the lock-up clutch keeps the hydraulic torque converter in a locked state. At this time, the hydraulic torque converter achieves a high-efficiency direct mechanical transmission mode.

[0018] S4. The shift control process of the transmission switching from hydraulic torque converter mode to direct mechanical transmission mode is as follows: When the vehicle starts, it usually starts in hydraulic torque converter mode. As the vehicle speed increases, the pump wheel speed and turbine speed gradually approach each other. When the difference between the turbine speed and the pump wheel speed is small enough, the hydraulic torque converter locks up and switches to direct mechanical transmission mode.

[0019] S5. The shift control process of the transmission switching from direct mechanical transmission mode to hydraulic torque converter mode is as follows: During normal driving, the direct mechanical transmission mode is generally used. When the vehicle speed gradually decreases to a certain lower limit, if the accelerator pedal opening is large and indicates a large torque demand, the hydraulic torque converter is unlocked and switches to hydraulic torque converter mode.

[0020] The beneficial effects of the dual-mode electric vehicle transmission and shifting method provided in this application are as follows: Compared with existing electric vehicles without a shifting mechanism, the transmission of this application can significantly enhance the climbing performance and increase the maximum speed of the electric vehicle. Compared with other existing two-speed transmissions, the application of its hydraulic torque converter mode can avoid overheating of the motor due to stall and reduce the slippage work on the clutch friction plates during shifting; therefore, the transmission of this application has a significant effect on improving the service life of the motor and the clutch plates, resulting in higher overall vehicle reliability.

[0021] The transmission in this application effectively utilizes the torque conversion function of a hydraulic torque converter and the power coupling function of a planetary gear mechanism. In hydraulic torque conversion mode, the transmission is equivalent to a planetary gear reducer superimposed with a hydraulic torque converter. The input torque is split into two parts: the torque transmitted from the pump impeller to the turbine and then to the large ring gear of the planetary gear mechanism is amplified by the torque conversion function of the hydraulic torque converter. The torque from the pump impeller to the pump impeller shaft and then to the sun gear is also amplified by the reduction relationship between the sun gear and the planetary carrier. The two parts of torque from the large ring gear and the sun gear work together on the planetary gears and output a larger torque from the planetary carrier, increasing the driving torque of the electric vehicle.

[0022] In hydraulic transmission mode, the motor speed and vehicle speed are decoupled. When the vehicle speed is zero, the motor speed can be non-zero, preventing damage from overheating due to stalled operation and improving overall vehicle reliability. During rapid acceleration from a standstill, the torque converter is unlocked in a timely manner based on the vehicle's power requirements, utilizing its torque-converting properties to increase drive torque and improve starting performance. Under normal driving conditions, the torque converter is locked, improving the efficiency of the entire transmission system. In summary, the dual-mode electric vehicle transmission of this application significantly improves the climbing performance, acceleration performance, driving comfort, and service life of electric vehicles. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structural composition of a dual-mode transmission for electric vehicles provided in an embodiment of this application;

[0025] Figure 2 This is a flowchart illustrating the switching of the working state of a dual-mode transmission for electric vehicles provided in an embodiment of this application.

[0026] The following are the labeling elements in the figure:

[0027] 1. Planetary carrier; 2. Sun gear; 3. Turbine shaft; 4. Output shaft; 5. Planetary gear set; 6. Large ring gear; 7. Pump wheel bushing; 8. Pump wheel; 9. Turbine; 10. Damping spring; 11. Input shaft; 12. Lock-up clutch; 13. Oil pump; 14. Oil pump motor; 15. Controller; 16. Reduction mechanism; 17. Differential. Detailed Implementation

[0028] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0029] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0030] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0032] like Figure 1As shown, a dual-mode transmission for an electric vehicle provided in this application embodiment will now be described. This dual-mode transmission for an electric vehicle includes: a controller 15, a torque converter with a lock-up clutch 12, a planetary gear mechanism, a reduction mechanism 16, and a differential 17. The controller 15 is electrically connected to the lock-up clutch 12 and is used to control the locking or unlocking of the lock-up clutch 12. The torque converter also includes an input shaft 11, a pump wheel 8, a turbine 9, and an output shaft 4. The planetary gear mechanism includes a sun gear 2, a large ring gear 6, a planetary gear set 5, and a planet carrier 1. One end of the input shaft 11 is connected to a drive motor, and the other end is connected to the pump wheel 8. The pump wheel 8 and the turbine 9 are driven together and locked or unlocked by the lock-up clutch 12. The pump wheel 8 is driven together with the sun gear 2. The turbine 9 is driven together with the large ring gear 6. The large ring gear 6 and the sun gear 2 are driven together with the planetary gear set 5 and the planet carrier 1. The planet carrier 1 is connected to the output shaft 4. The output shaft 4 is connected to the reduction mechanism 16 and outputs power to the wheels via the differential 17.

[0033] Specifically, the pump wheel 8 is connected to the sun gear 2 via the pump wheel bushing 7. The turbine 9 is connected to the large gear ring 6 via the turbine shaft 3, with one end of the turbine shaft 3 connected to the turbine 9 and the other end connected to the large gear ring 6.

[0034] In this embodiment, the two transmission modes of the electric vehicle dual-mode transmission are: hydraulic torque converter transmission mode and direct mechanical transmission mode.

[0035] In the hydraulic torque converter transmission mode, the lock-up clutch 12 unlocks the pump wheel 8 and turbine 9. The torque from the drive motor is input from the input shaft 11 to the pump wheel 8 and then splits into two parts. One part is transmitted to the sun gear 2 via the pump wheel bushing 7, and the other part is transmitted from the turbine 9 via the turbine shaft 3 to the large ring gear 6 after hydraulic torque conversion. The sun gear 2 and the large ring gear 6 transmit the obtained torque to the planetary gear set 5 and then to the output shaft 4 via the planet carrier 1. The output shaft 4 drives the vehicle via the reduction mechanism 16 and the differential 17, realizing speed reduction transmission. This hydraulic torque converter transmission mode is used for the low-speed gears of electric vehicles to realize the hydraulic continuously variable transmission of the gearbox, mainly used for starting and climbing, which require large driving torque.

[0036] In hydraulic torque converter mode, lock-up clutch 12 disengages, sun gear 2 rotates at the same speed as pump wheel 8, and large ring gear 6 rotates at the same speed as turbine 9. Pump wheel 8 rotates at a higher speed than turbine 9, and simultaneously, sun gear 2 rotates at a higher speed than large ring gear 6. Planetary carrier 1 rotates at a lower speed than sun gear 2 but higher speed than turbine 9. At this time, the input speed of the transmission is the speed of sun gear 2, and the output speed of the transmission is the speed of planetary carrier 1, thus achieving the reduction and torque increase transmission of the transmission; this is the hydraulic torque converter mode. During the hydraulic torque converter transmission process, turbine 9 gradually increases in speed, and the speeds of pump wheel 8 and turbine 9 gradually approach each other. At the same time, the speeds of sun gear 2 and large ring gear 6 gradually approach each other, and the speed of planetary carrier 1 also gradually approaches the speed of sun gear 2. The effect is that the speed of the drive motor gradually approaches the speed of the drive motor in the mechanical transmission mode at the current vehicle speed, and then the hydraulic torque converter is locked to switch to the mechanical transmission mode. The shifting impact is significantly reduced, the wear of the clutch friction plates is small, which helps to extend the service life of the transmission.

[0037] In the direct mechanical transmission mode, the lock-up clutch 12 locks the pump wheel 8 and turbine 9 together, and simultaneously locks the sun gear 2 and large ring gear 6 together. The planetary carrier 1 rotates at the same speed as the sun gear 2 and large ring gear 6, causing the input shaft 11, pump wheel 8, turbine 9, sun gear 2, large ring gear 6, planetary carrier 1, and output shaft 4 to rotate at the same speed. The torque of the drive motor is transmitted from the input shaft 11 to the output shaft 4 at a constant speed of 1:1. This mode is used for the high-speed gear of electric vehicles, mainly for medium-to-high-speed driving and low-speed conditions where large drive torque is not required. The drive torque of the drive motor is directly transmitted to the reduction mechanism 16, resulting in high transmission efficiency and achieving high-efficiency pure electric driving.

[0038] In this embodiment, the hydraulic torque converter is driven by the oil pump motor 14 to provide working oil pressure to the oil pump 13. The oil pump motor 14 is electrically connected to the controller 15, and the controller 15 controls the operation of the oil pump motor 14.

[0039] In this embodiment, a damping spring 10 is installed on the damping disc connected to the turbine.

[0040] like Figures 1-2 As shown, this embodiment also provides a gear shifting method based on the above-mentioned dual-mode electric vehicle transmission. The gear shifting method includes the following steps:

[0041] S1. Controller 15 collects accelerator pedal signal, vehicle speed, drive motor speed and drive motor temperature parameters. First, it determines whether the vehicle is traveling at low speed. If it is traveling at medium or high speed, it controls the lock-up clutch 12 to lock the torque converter, and the transmission is in direct mechanical transmission mode. If it is traveling at low speed, it continues to determine whether a large torque demand is required. If a large torque demand is not required, it controls the lock-up clutch 12 to lock the torque converter, and the transmission is in direct mechanical transmission mode. If a large torque demand is required, it controls the lock-up clutch 12 to unlock the torque converter, and the transmission is in torque converter transmission mode.

[0042] S2, the controller 15 determines whether the vehicle is in a long-term low-speed climbing condition based on the collected signal data such as vehicle speed, drive motor speed, drive motor torque, and drive motor temperature. If it is in a long-term low-speed climbing condition, the temperature rise of the drive motor will be large. At this time, the controller controls the lock-up clutch 12 to unlock the hydraulic torque converter. After the hydraulic torque converter is unlocked, the drive motor works at a higher speed, the drive motor efficiency is higher, and the temperature rise is reduced. At the same time, the hydraulic torque converter works in hydraulic torque converter transmission mode, which has the function of deceleration and torque increase, and the motor torque is improved, which is more suitable for climbing.

[0043] S3. Except for low-speed, high-torque demand conditions and excessive motor temperature rise, the lock-up clutch 12 keeps the hydraulic torque converter in a locked state. At this time, the hydraulic torque converter achieves a high-efficiency direct mechanical transmission mode.

[0044] S4. The shift control process of the transmission switching from hydraulic torque converter mode to direct mechanical transmission mode is as follows: When the vehicle starts, it usually starts in hydraulic torque converter mode. As the vehicle speed increases, the speed of pump wheel 8 and turbine 9 gradually approach each other. When the difference between the speed of turbine 9 and pump wheel 8 becomes small enough, the hydraulic torque converter locks up and switches to direct mechanical transmission mode.

[0045] S5. The shift control process of the transmission switching from direct mechanical transmission mode to hydraulic torque converter mode is as follows: During normal driving, the direct mechanical transmission mode is generally used. When the vehicle speed gradually decreases to a certain lower limit, if the accelerator pedal opening is large and indicates a large torque demand, the hydraulic torque converter is unlocked and switches to hydraulic torque converter mode.

[0046] In this embodiment, the transmission has two transmission modes: one is the hydraulic torque converter transmission mode, and the other is the direct mechanical transmission mode.

[0047] The hydraulic torque converter transmission mode is used when the vehicle is climbing hills at low speeds or accelerating rapidly from a standstill, requiring high driving torque. By controlling the rotation of the oil pump 13 motor, the oil pump 13 is driven to work, providing unlocking pressure to the hydraulic torque converter, allowing it to unlock and operate in hydraulic torque converter mode. In the hydraulic torque converter transmission mode, the transmission ratio changes. Initially, the transmission ratio is at its maximum during the hydraulic torque converter process, then gradually decreases until it approaches 1:1, at which point the hydraulic torque converter is locked. This achieves deceleration transmission, increases torque, and improves the vehicle's climbing and acceleration performance. Taking a zero-speed start as an example, when the hydraulic torque converter is unlocked, the turbine 9 initially rotates to zero speed, the large ring gear 6 also rotates to zero speed, and the pump wheel 8 drives the sun gear 2 in the planetary gear mechanism at a speed n. s Rotation, the output speed of planetary carrier 1 is n p The reduction ratio of the transmission is the reduction ratio between the sun gear 2 and the planet carrier 1. This reduction ratio depends on the relationship between the number of teeth on the sun gear 2 and the number of teeth on the large ring gear 6. For example, when the sun gear 2 has 28 teeth and the large ring gear 6 has 72 teeth, the theoretical reduction ratio can reach 3.57. Therefore, in the process of hydraulic torque converter transmission, the transmission ratio gradually decreases from 3.57 to close to 1 in hydraulic torque converter mode.

[0048] When the vehicle does not require a large driving torque, the hydraulic torque converter is locked, and the transmission operates in mechanical transmission mode, improving transmission efficiency through direct mechanical transmission.

[0049] In this embodiment, the hydraulic torque converter gear is defined as the low-speed gear, and the mechanical transmission gear is defined as the high-speed gear.

[0050] The upshift control process is as follows: When the vehicle accelerates rapidly from a standstill, it operates in torque converter mode, at which point the lock-up clutch 12 disengages; when the vehicle accelerates to a certain speed and needs to switch to mechanical transmission mode, the lock-up clutch 12 engages, and the vehicle enters mechanical transmission mode. The advantage of mechanical transmission mode is its high transmission efficiency, and the transmission will operate in mechanical transmission mode in most situations.

[0051] The downshift control process is as follows: When the vehicle is traveling at a higher speed, the mechanical transmission gear is used, and the lock-up clutch 12 is engaged. When the vehicle decelerates to a lower speed and the driver's accelerator pedal action indicates a need for greater drive torque, the hydraulic torque converter gear is engaged. At this time, the lock-up clutch 12 is disengaged, and the vehicle is in hydraulic torque converter mode. After switching to hydraulic transmission mode, the rotational speed of the drive motor rotor can increase rapidly, and the motor outputs greater power to drive the vehicle, giving it better acceleration performance.

[0052] When using the torque converter mode, this transmission can increase the torque and speed of the drive motor, preventing the motor from stalling and causing damage. This improves climbing and acceleration performance while enhancing the reliability and extending the lifespan of the electric vehicle.

[0053] This transmission has high transmission efficiency when using mechanical gears. Therefore, as long as the output torque of the drive motor can meet the driving requirements, the mechanical gears are used. For example, during non-rapid acceleration starts, the motor's output torque can meet the driving requirements, and even at low speeds, the hydraulic torque converter lock-up clutch is directly engaged to improve transmission efficiency.

[0054] In summary, this dual-mode transmission for electric vehicles can achieve both hydraulic torque converter transmission and mechanical transmission modes. It features a simple structure, convenient control, comprehensive functions, and outstanding performance, effectively meeting the requirements of electric vehicles for acceleration, hill-climbing performance, and top speed.

[0055] The control process of the transmission is as follows Figure 2 As shown, after the program starts, it collects parameters such as accelerator pedal signal, vehicle speed, motor speed, and motor temperature, and then determines whether the vehicle is traveling at low speed. If it is not traveling at low speed, it locks the torque converter, and the transmission operates in mechanical transmission mode. If it is traveling at low speed, it continues to determine whether there is a high torque demand. If there is a high torque demand, it unlocks the torque converter, disengaging the lock-up clutch 12, and the transmission operates in torque converter transmission mode. If there is no high torque demand, it continues to determine whether the motor temperature rise is too high. If the motor temperature rise is too high, it unlocks the torque converter, disengaging the lock-up clutch 12, and the transmission operates in torque converter transmission mode. If the motor temperature rise is not high, it locks the torque converter, and the transmission operates in mechanical transmission mode.

[0056] The above description is merely a preferred embodiment of this application and is not intended to limit the application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application. For example, replacing the hydraulic torque converter with a lock-up function with a hydraulic torque converter without a lock-up clutch, and simultaneously setting a clutch on the planetary gear mechanism to lock any two of the sun gear, planet carrier, and large ring gear together, can achieve the same effect as this solution.

Claims

1. A dual-mode transmission for electric vehicles, characterized in that, include: The system comprises a controller (15), a hydraulic torque converter with a lock-up clutch (12), a planetary gear mechanism, a reduction mechanism (16), and a differential (17). The controller (15) controls the unlocking / locking of the lock-up clutch (12). The hydraulic torque converter also includes an input shaft (11), a pump wheel (8), a turbine (9), and an output shaft (4). The planetary gear mechanism includes a sun gear (2), a large ring gear (6), a planetary gear set (5), and a planet carrier (1). One end of the input shaft (11) is connected to a drive motor, and the other end is connected to the pump wheel (8). The pump wheel (8) and the turbine (9) are connected by fluid transmission and through the differential. The lock-up clutch (12) is locked or unlocked. The pump wheel (8) is driven by the sun gear (2). The turbine (9) is driven by the large ring gear (6). The large ring gear (6) and the sun gear (2) are driven by the planetary gear set (5) and the planet carrier (1). The planet carrier (1) is connected to the output shaft (4). The output shaft (4) is connected to the reduction mechanism (16) and outputs power to the wheels through the differential (17). The pump wheel (8) is driven by the sun gear (2) through the pump wheel bushing (7). The turbine (9) is driven by the large ring gear (6) through the turbine shaft (3).

2. The dual-mode transmission for electric vehicles as described in claim 1, characterized in that: The first transmission mode of the transmission is the hydraulic torque converter transmission mode. The lock-up clutch (12) unlocks the pump wheel (8) and the turbine (9). The torque of the drive motor is input from the input shaft (11) to the pump wheel (8) and then splits into two parts. One part is transmitted to the sun gear (2) through the pump wheel bushing (7), and the other part is transmitted from the turbine (9) through the turbine shaft (3) to the large ring gear (6) after hydraulic torque converter. The sun gear (2) and the large ring gear (6) transmit the obtained torque to the planetary gear set (5) and then to the output shaft (4) through the planet carrier (1). The output shaft (4) drives the vehicle through the reduction mechanism (16) and the differential (17) to achieve reduction transmission.

3. The dual-mode transmission for electric vehicles as described in claim 2, characterized in that: The second transmission mode of the transmission is a direct mechanical transmission mode. The lock-up clutch (12) locks the pump wheel (8) and the turbine (9) together. At the same time, it also locks the sun gear (2) and the large ring gear (6) together. The planet carrier (1) rotates at the same speed as the sun gear (2) and the large ring gear (6), so that the input shaft (11), pump wheel (8), turbine (9), sun gear (2), large ring gear (6), planet carrier (1) and output shaft (4) all rotate at the same speed. The torque of the drive motor is transmitted from the input shaft (11) to the output shaft (4) at a constant speed with a transmission ratio of 1:

1.

4. The dual-mode transmission for electric vehicles as described in claim 1, characterized in that: The hydraulic torque converter is powered by an oil pump (13) driven by an oil pump motor (14), which provides working oil pressure. The oil pump motor (14) is electrically connected to the controller (15).

5. The dual-mode transmission for electric vehicles as described in claim 1, characterized in that: A damping spring (10) is provided on the damping disc connected to the turbine (9).

6. A method for shifting gears in an electric vehicle based on a dual-mode transmission according to any one of claims 1-5, characterized in that, Includes the following steps: S1. The controller (15) collects the accelerator pedal signal, vehicle speed, drive motor speed and drive motor temperature parameters. First, it determines whether the vehicle is driving at low speed. If it is driving at medium or high speed, it controls the lock-up clutch (12) to lock the hydraulic torque converter, and the transmission is in direct mechanical transmission mode. If it is driving at low speed, it continues to determine whether a large torque demand is required. If there is no large torque demand, it controls the lock-up clutch (12) to lock the hydraulic torque converter, and the transmission is in direct mechanical transmission mode. If there is a large torque demand, it controls the lock-up clutch (12) to unlock the hydraulic torque converter, and the transmission is in hydraulic torque converter transmission mode. S2. The controller (15) determines whether the vehicle is in a long-term low-speed climbing condition based on the signal data collected in step S1. If it is in a long-term low-speed climbing condition, the temperature rise of the drive motor will be large. At this time, the lock-up clutch (12) is controlled to unlock the hydraulic torque converter. After the hydraulic torque converter is unlocked, the drive motor works at a higher speed, the drive motor efficiency is higher, and the temperature rise is reduced. At the same time, the hydraulic torque converter works in the hydraulic torque converter transmission mode, which has the function of deceleration and torque increase. The motor torque is improved and better suited to the needs of climbing. S3. Except for low-speed, high-torque demand conditions and excessive motor temperature rise, the lock-up clutch (12) keeps the hydraulic torque converter in a locked state. At this time, the hydraulic torque converter achieves a high-efficiency direct mechanical transmission mode. S4. The shift control process of the transmission from hydraulic torque converter mode to direct mechanical transmission mode is as follows: When the vehicle starts, it usually starts in hydraulic torque converter mode. As the vehicle speed increases, the speed of pump wheel (8) and turbine (9) gradually approach each other. When the difference between the speed of turbine (9) and pump wheel (8) is small enough, the hydraulic torque converter locks up and switches to direct mechanical transmission mode. S5. The shift control process when the transmission switches from direct mechanical drive mode to hydraulic torque converter mode is as follows: During normal driving, the direct mechanical transmission mode is generally used. When the vehicle speed gradually decreases to a certain lower limit, if the accelerator pedal is opened too wide to indicate a large torque demand, the torque converter will unlock and switch to torque converter mode.

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