A multi-gear oil-cooled electric drive axle system efficiency improvement method

Abstract

The embodiment of the application provides a multi-gear oil-cooled electric drive axle system efficiency improving method, wherein the loss of the electric drive axle transmission is considered during calibration, the wheel end torque is measured, and the influence of the water pump flow and the cooling oil temperature on the whole axle efficiency is considered. Therefore, the operation of the electric drive axle system is controlled through the data calibrated in advance, and the whole system efficiency is in a better state by further considering the water pump loss, so that the energy utilization rate is further improved, and the driver experience is improved.

Description

Technical Field

[0001] This invention relates to the field of electric drive bridge systems, and more particularly to a method for improving the efficiency of a multi-speed oil-cooled electric drive bridge system. Background Technology

[0002] With the development of integrated new energy commercial vehicles, the electric drive axle, as a key assembly integrating a motor, reducer, differential, and other components, provides power for the entire vehicle, and its application scope and market share are continuously increasing. In this context, the performance and system efficiency of the electric drive axle have a crucial impact on vehicle operation.

[0003] In related technologies, the calibrated efficiency of the motor-control system is generally used only to determine the torque output to the motor's wheel ends and to execute corresponding shifting strategies. The problem with this approach is that, because the impact of differential mechanical losses and multi-speed gearbox gear meshing losses on the drive system efficiency during the electric drive axle transmission process is not considered, the actual output torque at the wheel ends is prone to deviating from the expected torque when calculating the motor's output torque. This makes it difficult to ensure that the electric drive axle transmission system operates within a high-efficiency range when executing shifting strategies. Furthermore, for vehicles with two or more electric drive axles, the distribution of torque among these axles must also consider the overall efficiency of the electric drive axle system. This can lead to inefficient operation, wasting energy, causing wear and tear on the vehicle, and resulting in a poor driving experience. Summary of the Invention

[0004] This invention provides a method for improving the efficiency of a multi-speed oil-cooled electric drive axle system, so that the overall efficiency of the vehicle can be maximized during operation, thereby improving energy utilization, enhancing the driving experience, and extending the vehicle's lifespan.

[0005] According to one aspect of the present invention, a method for improving the efficiency of a multi-speed oil-cooled electric drive axle system is provided, wherein the multi-speed oil-cooled electric drive axle system includes: a gearbox controller, a shift actuator and a motor controller respectively connected to the gearbox controller, a motor connected to the motor controller, an oil cooling component and a water cooling component, wherein the oil cooling component is used to cool the shift actuator, and the water cooling component is used to cool the oil cooling component, the motor and the motor controller;

[0006] The method includes:

[0007] Determine the current operating condition of the vehicle, wherein the operating parameters under the current operating condition include the vehicle gear, motor speed and motor torque;

[0008] The system calls upon the correspondence between the overall bridge efficiency calibrated under the current operating conditions and the cooling oil temperature in the oil-cooled assembly, as well as the correspondence between the cooling oil temperature and the water pump flow rate in the water-cooled assembly.

[0009] Extract the current cooling oil temperature corresponding to the highest overall bridge efficiency under the current operating conditions, and the current water pump flow rate corresponding to the current cooling oil temperature;

[0010] Control the water-cooling assembly to operate at the current water pump flow rate, and collect the cooling oil temperature of the oil-cooling assembly; and time the process;

[0011] Within a first preset time period, the water-cooling component is controlled to run for the same amount of time at the current water pump flow rate, the current water pump flow rate plus the first step long flow rate, and the current water pump flow rate minus the first step long flow rate. The first water pump flow rate corresponding to the highest overall efficiency is determined, and the water-cooling component is controlled to continue running at the first water pump flow rate. The overall efficiency is the efficiency after adding the overall bridge efficiency to the water pump loss.

[0012] Optionally, if the flow rate of the first water pump is the current water pump flow rate, then the water cooling component is controlled to continue operating at the current water pump flow rate;

[0013] If the first water pump flow rate is the value after increasing or decreasing the current water pump flow rate by a first step long flow rate, the method further includes: at a second preset time interval, continuing to adjust the first water pump flow rate by increasing or decreasing the first step long flow rate to the second water pump flow rate; and when the overall efficiency after adjustment is lower than before adjustment, controlling the water cooling component to continue operating with the first water pump flow rate, and when the overall efficiency after adjustment is higher than before adjustment, controlling the water cooling component to continue operating with the second water pump flow rate, and so on, until the current operating condition changes.

[0014] Optionally, the water-cooling assembly is controlled to operate at the current water pump flow rate, and the cooling oil temperature of the oil-cooling assembly is collected; after timing, the method further includes:

[0015] When the temperature of the cooling oil exceeds a preset threshold range, the water cooling component is controlled to operate at a preset flow rate fluctuating with the current water pump flow rate, and the search for the water pump flow rate corresponding to the highest overall efficiency is completed.

[0016] Optionally, the operating parameters also include vehicle speed, and after extracting the current cooling oil temperature corresponding to the highest overall bridge efficiency, the parameters also include:

[0017] The system retrieves the corresponding relationship between the vehicle gear, axle efficiency, and vehicle speed at the current cooling oil temperature, and adjusts the vehicle gear based on the vehicle speed under the current operating conditions and the axle efficiency corresponding to the vehicle speed. The axle efficiency is the ratio of wheel-end output power to motor DC input power.

[0018] Alternatively, the corresponding relationship between vehicle gear, wheel torque, and vehicle speed at the current cooling oil temperature can be invoked, and the vehicle gear can be adjusted based on the vehicle speed under the current operating conditions and the wheel torque corresponding to the vehicle speed, wherein the wheel torque is obtained by actual measurement during calibration.

[0019] Optionally, adjusting the vehicle's gear based on the vehicle speed under the current operating conditions and the corresponding bridge efficiency includes:

[0020] The corresponding relationship between the vehicle gear, bridge efficiency and vehicle speed has a corresponding shift node. When the vehicle speed is at the speed value corresponding to the shift node, the vehicle gear is adjusted.

[0021] Adjusting the vehicle's gear based on the current vehicle speed and the corresponding wheel torque includes:

[0022] The corresponding relationship between the vehicle gear, wheel torque and vehicle speed has a corresponding shift node. When the vehicle speed is at the speed value corresponding to the shift node, the vehicle gear is adjusted.

[0023] Optionally, the multi-stage oil-cooled electric drive bridge system includes at least two electric drive bridges, and the method further includes:

[0024] By calling up the corresponding relationship between the motor speed, wheel end torque, and motor torque of each electric drive axle under the current cooling oil temperature and the vehicle's gear position, the wheel end torque of different electric drive axles is obtained to calculate the total wheel end output torque of the vehicle.

[0025] The system retrieves the correspondence between the vehicle speed, wheel end torque, and overall axle efficiency of each electric drive axle under the current cooling oil temperature and the vehicle's gear position. Based on the overall axle efficiency and the total wheel end output torque corresponding to different electric drive axles, and under the condition that the sum of the overall axle efficiencies of each electric drive axle is maximized, the system redistributes different wheel end torques to different electric drive axles.

[0026] The operation of each electric drive axle is controlled by the distributed wheel-end torque.

[0027] Optionally, based on the overall axle efficiency and the total wheel-end output torque corresponding to different electric drive axles, and under the condition that the sum of the overall axle efficiencies of each electric drive axle is maximized, the redistribution of different wheel-end torques to different electric drive axles includes:

[0028] If the total output torque at the wheel end is T, and the electric drive axle includes a first electric drive axle and a second electric drive axle, and the torque allocated to the first electric drive axle is T×a, and the corresponding efficiency of the first electric drive axle is η(a), then the torque allocated to the second electric drive axle is T×(1-a), and the corresponding efficiency of the second electric drive axle is η(1-a).

[0029] Iterate through a from 0 to 1 to minimize T×a / η(a) + T×(1-a) / η(1-a) to satisfy the condition that the sum of the overall bridge efficiency of each electric drive bridge is maximized.

[0030] Optionally, controlling the operation of the electric drive axle with the distributed wheel-end torque includes:

[0031] After assigning different wheel-end torques to different electric drive axles, the wheel-end torques of different electric drive axles are linearly adjusted, and the motor torques associated with the corresponding electric drive axles are non-linearly adjusted.

[0032] Optionally, before determining the current operating condition of the vehicle, the following steps are also included:

[0033] Based on the motor calibration bench, the corresponding relationship between motor speed, motor torque and electronic control efficiency is calibrated;

[0034] Based on the bridge abutment, under given gear, motor speed, and motor torque, the corresponding multi-dimensional data correspondence between water pump flow rate, cooling lubricating oil temperature, wheel end torque, electric drive axle wheel end speed, electric drive axle wheel end output power, overall axle efficiency, electronic control temperature, motor temperature, and vehicle speed is calibrated.

[0035] Optionally, the water-cooling assembly includes a water pump, a radiator, and water channels;

[0036] The water pump inlet is connected to the radiator outlet, the water pump outlet is connected to the water inlet of the water channel in the motor controller, the water channel outlet in the motor controller is connected to the water inlet of the water channel in the motor, and the water channel outlet in the motor is connected to the radiator inlet.

[0037] The motor is also equipped with a heat exchanger, which is connected to the oil cooling assembly and the water channel in the motor respectively;

[0038] The oil cooling assembly includes a housing, cooling lubricating oil, and a temperature sensor. The housing contains a shift actuator and the cooling lubricating oil, and the temperature sensor is used to measure the oil temperature of the cooling lubricating oil.

[0039] This invention provides a method for improving the efficiency of a multi-speed oil-cooled electric drive axle system. The multi-speed oil-cooled electric drive axle system includes: a transmission controller, a shift actuator and a motor controller connected to the transmission controller, a motor connected to the motor controller, an oil-cooling component, and a water-cooling component. The oil-cooling component cools the shift actuator, and the water-cooling component cools the oil-cooling component, the motor, and the motor controller. The method includes: determining the current operating condition of the vehicle, where operating parameters include the vehicle gear, motor speed, and motor torque; invoking the correspondence between the overall axle efficiency calibrated under the current operating condition and the cooling oil temperature in the oil-cooling component; and... The system establishes a correlation between oil cooling temperature and water pump flow rate in the water-cooled components. It extracts the current cooling oil temperature and corresponding water pump flow rate at which the overall axle efficiency is highest under current operating conditions. The system controls the water-cooled components to operate at the current water pump flow rate and collects the cooling oil temperature of the oil-cooled components. Timing is then performed. Within a first preset time period, the water-cooled components are controlled to operate at the current water pump flow rate, with the current water pump flow rate increased by a first-step flow rate, and with the current water pump flow rate decreased by a first-step flow rate for the same duration. The first water pump flow rate corresponding to the highest overall efficiency is determined, and the water-cooled components are controlled to continue operating at this first flow rate. The overall efficiency is the sum of the overall axle efficiency and the water pump losses. Therefore, this electric drive axle system not only considers the overall axle efficiency in advance, operating when the overall axle efficiency is high, but also takes water pump losses into account during operation. By adjusting the water pump flow rate, it affects the cooling oil temperature, further influencing the overall axle efficiency. By comprehensively considering the impact of water pump losses on the overall axle efficiency, the electric drive axle system operates at a high overall efficiency, improving energy utilization and enhancing the driver experience.

[0040] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the structure of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention;

[0043] Figure 2 This is a flowchart of a method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention;

[0044] Figure 3 The curve showing the change of overall loss with increasing water pump flow rate in the multi-stage oil-cooled electric drive bridge system efficiency improvement method proposed in the embodiments of the present invention;

[0045] Figure 4 This is a shifting diagram in a method for improving the efficiency of a multi-speed oil-cooled electric drive bridge system according to an embodiment of the present invention.

[0046] Figure 5 This is a shifting diagram in a method for improving the efficiency of a multi-speed oil-cooled electric drive bridge system according to another embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of the vehicle speed, wheel end torque, and overall bridge efficiency of a single axle in the multi-speed oil-cooled electric drive axle system efficiency improvement method proposed in the embodiments of the present invention.

[0048] Figure 7 This is a schematic diagram showing the relationship between the wheel end torque and motor torque of a single axle in the efficiency improvement method of a multi-speed oil-cooled electric drive axle system proposed in an embodiment of the present invention.

[0049] Figure 8 This is a schematic diagram of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented 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.

[0052] Figure 1This is a schematic diagram of the structure of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention; as shown. Figure 1 As shown, the multi-speed oil-cooled electric drive axle system includes: a gearbox controller 101, a shift actuator 102 and a motor controller 103 respectively connected to the gearbox controller 101, a motor 104 connected to the motor controller 103, an oil cooling assembly 105 and a water cooling assembly 106, wherein the oil cooling assembly 105 is used to cool the shift actuator 102, and the water cooling assembly 106 is used to cool the oil cooling assembly 105, the motor 104 and the motor controller 103.

[0053] The transmission controller 101 and the motor controller 103 can communicate with each other. The transmission controller 101 can obtain control parameters for the motor 104 from the motor controller 103, and / or feedback parameters of the motor 104. The motor controller 103 can obtain control parameters for the shift actuator 102 from the transmission controller 101, and / or feedback parameters of the shift actuator 102. The transmission controller 101 controls the shift actuator 102, and the motor controller 103 controls the motor 104. The motor 104 drives the multi-speed oil-cooled electric drive axle. The shift actuator 102 is located in the oil cooling assembly 105, which cools the shift actuator 102. The heat generated by the shift actuator 102 is transferred from the oil cooling assembly 105 to the water channels in the motor 104 via a heat exchanger. The water cooling assembly 106 is also used to cool the motor controller 103 and the motor 104.

[0054] The above is an introduction to the multi-speed oil-cooled electric drive bridge system. The following describes methods for improving the efficiency of this multi-speed oil-cooled electric drive bridge system.

[0055] Figure 2 This is a flowchart of a method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention; such as Figure 1 As shown, the method includes:

[0056] S101, determine the current operating condition of the vehicle. The operating parameters under the current operating condition include the vehicle gear, motor speed and motor torque.

[0057] The motor speed can be acquired by a motor speed sensor and then obtained through the motor controller. The vehicle gear position can be acquired by a gear position sensor or gear switch and then obtained through the transmission controller. The motor torque can be acquired by a torque sensor and then obtained through the motor controller.

[0058] S102 calls up the correspondence between the overall bridge efficiency calibrated under the current operating conditions and the cooling oil temperature in the oil-cooled assembly, as well as the correspondence between the cooling oil temperature and the water pump flow rate in the water-cooled assembly.

[0059] The correspondence in step S102 can be pre-calibrated and stored in the vehicle controller. It is understood that during calibration, the vehicle's operating parameters can be controlled, and calibration can be performed under the corresponding operating parameters. The specific calibration process will be elaborated in subsequent sections and will not be detailed here.

[0060] S103, extract the current cooling oil temperature corresponding to the highest overall bridge efficiency under the current operating conditions, and the current water pump flow rate corresponding to the current cooling oil temperature.

[0061] In step S102, the correspondence is that under the current operating conditions, different cooling oil temperatures correspond to different overall bridge efficiencies, as well as different water pump flow rates. In order to improve the efficiency of the multi-speed oil-cooled electric drive bridge system, the cooling oil temperature and water pump flow rate corresponding to the highest overall bridge efficiency under this operating condition can be selected, so that the overall efficiency of the multi-speed oil-cooled electric drive bridge system can also be improved accordingly during operation.

[0062] S104 controls the water-cooled components to operate at the current water pump flow rate and collects the cooling oil temperature of the oil-cooled components; and performs timing.

[0063] S105, within the first preset time period, control the water-cooling component to run for the same amount of time at the current water pump flow rate, the current water pump flow rate plus the first step long flow rate, and the current water pump flow rate minus the first step long flow rate, determine the first water pump flow rate corresponding to the highest overall efficiency, and control the water-cooling component to continue running at the first water pump flow rate. The overall efficiency is the efficiency of the entire bridge plus the efficiency after water pump loss.

[0064] It should be noted that although the overall efficiency of the bridge is highest when the water-cooled components are controlled by the current calibrated water pump flow rate, the overall efficiency may not be the highest. Therefore, it is crucial to find the water pump flow rate that corresponds to the highest overall efficiency when controlling the operation of the water-cooled components.

[0065] In other words, the water pump flow rate and cooling oil temperature during the operation of the water-cooled components correspond to the data at which the overall bridge efficiency is highest. However, to ensure the highest overall efficiency of the multi-speed oil-cooled electric drive bridge system during operation, the following steps can be performed to find the highest overall efficiency: First, after controlling the water-cooled components to run at the current water pump flow rate for a first preset duration, record the overall bridge efficiency and water pump power consumption of the multi-speed oil-cooled electric drive bridge. Then, control the water-cooled components to run at the current water pump flow rate increased by the first preset duration for another first preset duration, and record the overall bridge efficiency and water pump power consumption again. Next, control the water-cooled components to run at the current water pump flow rate decreased by the first preset duration for another first preset duration, and record the overall bridge efficiency and water pump power consumption again. After three runs, the water pump flow rate corresponding to the highest overall efficiency of the multi-speed oil-cooled electric drive bridge system can be selected. For example, the first preset duration is shorter than a first preset time period.

[0066] It's understandable that the overall efficiency of a multi-speed oil-cooled electric drive axle system refers to the comprehensive efficiency after considering the energy consumed by the water pump, based on the overall axle efficiency. The overall axle efficiency is the efficiency of the multi-speed oil-cooled electric drive axle system without considering water pump losses. The overall axle efficiency is the ratio of wheel-end output power to the motor's DC input power. Changing the water pump flow rate affects the cooling oil temperature, which in turn affects the transmission efficiency of the shift actuator, and further, the operating efficiency of the motor controller and the motor itself, thus impacting the overall axle efficiency. While consuming a certain amount of energy with the water pump may improve the overall axle efficiency, excessive energy consumption by the water pump can negatively affect the overall efficiency of the multi-speed oil-cooled electric drive axle system. Therefore, a comprehensive consideration of both the overall axle efficiency and water pump losses is necessary to maximize the overall efficiency of the multi-speed oil-cooled electric drive axle system. Figure 3 The curve showing the change in overall loss with increasing water pump flow rate in the multi-stage oil-cooled electric drive bridge system efficiency improvement method proposed according to an embodiment of the present invention is shown. Figure 3 As shown, it can be seen that the overall loss first decreases and then increases. The goal of this scheme is to find the point where the overall loss is the lowest, that is, the point where the overall efficiency is the highest.

[0067] In the above embodiment, the overall efficiency = (wheel-end output power - water pump power) / (motor DC input power - water pump power). Therefore, the overall efficiency under three different water pump flow rates can be compared, and the water pump flow rate corresponding to the highest overall efficiency can be selected to control the operation of the water-cooling components.

[0068] In the above embodiments, the first-step long flow rate can be set according to the actual situation, and generally does not exceed 50% of the current water pump flow rate.

[0069] In a specific embodiment, the total bridge loss q(t0) (input power multiplied by (1-efficiency)) of the electric drive bridge at the current time t0 and the current water pump power consumption w(t0) are recorded. The water pump flow rate is increased by Q + ΔQ, and after a certain period of time, the total bridge loss q(t1) of the electric drive bridge at the current time t1 and the current water pump power consumption w(t1) are recorded. The water pump flow rate is decreased by Q - ΔQ, and after a certain period of time, the total bridge loss q(t2) of the electric drive bridge at the current time t2 and the current water pump power consumption w(t2) are recorded. It can be determined which of the three times (t0, t1, and t2) has the lowest total loss. If the loss is suitable at t0, the water pump power consumption Q remains constant. If the loss is lowest at t1, Q should be increased. If the loss is lowest at t2, Q should be appropriately decreased.

[0070] Optionally, if the flow rate of the first water pump is the current water pump flow rate, then the water cooling component is controlled to continue operating based on the current water pump flow rate;

[0071] If the first water pump flow rate is the value after increasing or decreasing the current water pump flow rate by the first step long flow rate, the method further includes: at a second preset time interval, continuing to adjust the first water pump flow rate by increasing or decreasing the first step long flow rate to the second water pump flow rate; and when the overall efficiency after adjustment is lower than before adjustment, controlling the water cooling component to continue operating with the first water pump flow rate, and when the overall efficiency after adjustment is higher than before adjustment, controlling the water cooling component to continue operating with the second water pump flow rate, and so on, until the current operating condition changes.

[0072] Understandably, if a corresponding water pump flow rate has been selected after step S105, the operation of the water-cooled components can be controlled using that flow rate. To further find the limit of the overall efficiency of the multi-stage oil-cooled electric drive bridge system, the steps in this embodiment can be executed. That is, if the overall efficiency is the highest among the three after increasing the first-stage flow rate, then in subsequent processes, the first-stage flow rate can be increased further, and the overall efficiency corresponding to increasing the first-stage flow rate in the previous process can be compared accordingly. If the overall efficiency corresponding to the latter decreases, it indicates that the water pump flow rate corresponding to the former is already the water pump flow rate that achieves the highest overall efficiency. If the overall efficiency corresponding to the latter increases, then the first-stage flow rate can be increased further. This process continues until the water pump flow rate that achieves the highest overall efficiency is found. Similarly, if the overall efficiency is the highest among the three after decreasing the first-stage flow rate, then in subsequent processes, the first-stage flow rate can be decreased further, and the overall efficiency corresponding to decreasing the first-stage flow rate in the previous process can be compared accordingly. If the overall efficiency corresponding to the latter decreases, it indicates that the water pump flow rate corresponding to the former is already the water pump flow rate that achieves the highest overall efficiency. If the overall efficiency corresponding to the latter increases, then the first-stage flow rate can be decreased further. This process continues until the pump flow rate that maximizes overall efficiency is found is stopped.

[0073] In one specific embodiment, if the foregoing embodiment determines that the traffic should be increased, then:

[0074] Increase the water pump flow rate to Q + ΔQ, wait for a certain period of time, and record the total loss at the current time t21.

[0075] Increase the water pump flow rate to Q + 2 × ΔQ, wait for a certain period of time, and record the total loss at the current time t22.

[0076] If the total loss at time t21 is lower than that at time t22, then maintain the pump flow rate at Q + ΔQ, exit this step, and do not perform this step until the operating conditions change.

[0077] If the total loss at time t22 is lower than the total loss at time t21, then keep the pump flow rate at Q + 2 × ΔQ and continue executing this step, and so on.

[0078] If the aforementioned embodiment determines that the water pump flow rate should be reduced: then:

[0079] Reduce the water pump flow rate to Q-ΔQ, wait for a certain period of time, and record the total loss at the current time t21.

[0080] Reduce the water pump flow rate to Q-2×ΔQ, wait for a certain period of time, and record the total loss at the current time t22.

[0081] If the total loss at time t21 is lower than that at time t22, then maintain the pump flow rate at Q-ΔQ, exit this step, and do not perform this step until the operating conditions change.

[0082] If the total loss at time t22 is lower than the total loss at time t21, then keep the pump flow rate at Q-2×ΔQ and continue executing this step, and so on.

[0083] It is understandable that, to avoid endless searching and keeping the system in an unstable state, a search duration can be set. This duration can correspond to the duration of vehicle operating condition changes, or a portion of the duration under the same stable operating condition. The specific duration is determined based on factors such as the vehicle model.

[0084] Optionally, the water-cooled components are controlled to operate at the current water pump flow rate, and the cooling oil temperature of the oil-cooled components is collected; after timing, the following is also included:

[0085] When the cooling oil temperature exceeds the preset threshold range, the water cooling components are controlled to operate at the current water pump flow rate with a floating preset flow rate, and the search for the water pump flow rate corresponding to the highest overall efficiency is completed.

[0086] Understandably, while adjusting the water pump flow rate, the cooling oil temperature is continuously monitored to prevent overheating or undercooling of the motor, electronic control system, and shift actuator, which could cause system malfunctions. Furthermore, while adjusting the water pump flow rate to maximize the overall efficiency of the multi-speed oil-cooled electric drive bridge system (finding the maximum value during the process), if the cooling oil temperature exceeds a preset threshold range (e.g., 5°C higher than the preset value), the water-cooling components can be controlled to increase the preset flow rate at the current water pump flow rate. Conversely, if the cooling oil temperature exceeds a preset threshold range (e.g., 5°C lower than the preset value), the water-cooling components can be controlled to decrease the preset flow rate at the current water pump flow rate. The preset threshold range can be pre-calibrated, and the preset flow rate can be 20% of the current water pump flow rate.

[0087] Optionally, the operating parameters also include vehicle speed, and after extracting the current coolant temperature corresponding to the highest overall axle efficiency, they also include:

[0088] The system retrieves the corresponding relationship between vehicle gear, axle efficiency, and vehicle speed at the current cooling oil temperature. Based on the current vehicle speed and the corresponding axle efficiency, it adjusts the vehicle gear. The axle efficiency is the ratio of wheel-end output power to motor DC input power.

[0089] Alternatively, the corresponding relationship between vehicle gear, wheel torque, and vehicle speed at the current coolant temperature can be retrieved, and the vehicle gear can be adjusted based on the current vehicle speed and the corresponding wheel torque, wherein the wheel torque is obtained by actual measurement during calibration.

[0090] It should be noted that the correspondence in this embodiment can still be pre-calibrated, and the calibration process is detailed below. Vehicle speed can be collected by a vehicle speed sensor and obtained through the vehicle controller. Thus, at the corresponding cooling oil temperature, the overall axle efficiency is highest, or the wheel-end torque remains constant. Therefore, based on the above correspondence, the vehicle's gears can be adjusted to ensure the accuracy of the shift points of the multi-gear oil-cooled electric drive axle system, avoiding inconsistent power before and after gear shifts, thereby allowing the system to operate within its high-efficiency range.

[0091] Figure 4 This is a shifting diagram in a method for improving the efficiency of a multi-speed oil-cooled electric drive bridge system according to an embodiment of the present invention; as shown. Figure 4As shown, the horizontal axis represents vehicle speed, and the vertical axis represents overall bridge efficiency. Blue indicates the change in overall bridge efficiency as vehicle speed increases when the vehicle is in first gear. Dark yellow indicates the change in overall bridge efficiency as vehicle speed increases when the vehicle is in second gear. Gray indicates the change in overall bridge efficiency calculated based on motor and electronic control efficiency as vehicle speed increases when the vehicle is in first gear. Light yellow indicates the change in overall bridge efficiency calculated based on motor and electronic control efficiency as vehicle speed increases when the vehicle is in second gear. It can be seen that shifting based on the calibrated overall bridge efficiency (wheel-end output power / motor DC input power) results in shift points occurring in the lower efficiency range compared to shifting based on the overall bridge efficiency calculated using motor and electronic control efficiency (motor and electronic control efficiency × a fixed ratio). This not only improves shift point accuracy and reduces power inconsistencies before and after shifting, but also leads to better overall bridge efficiency after shifting.

[0092] Figure 5 This is a shifting diagram in a method for improving the efficiency of a multi-speed oil-cooled electric drive bridge system according to another embodiment of the present invention; as shown. Figure 5 As shown, the horizontal axis represents vehicle speed, and the vertical axis represents wheel-end torque. Blue indicates the change in wheel-end torque as vehicle speed increases when the vehicle is in first gear. Dark yellow indicates the change in wheel-end torque as vehicle speed increases when the vehicle is in second gear. Gray indicates the change in wheel-end torque calculated based on motor control efficiency as vehicle speed increases when the vehicle is in first gear. Light yellow indicates the change in wheel-end torque calculated based on motor control efficiency as vehicle speed increases when the vehicle is in second gear. It can be seen that shifting based on the calibrated wheel-end torque (obtained through actual measurement, for example, through a torque sensor) results in a lower shift point compared to shifting based on the wheel-end torque calculated using motor control efficiency (motor torque × speed ratio × motor control efficiency). This not only improves shift point accuracy and reduces power inconsistency before and after shifting, but also optimizes overall axle efficiency after shifting.

[0093] Optionally, adjusting the vehicle's gear based on the current vehicle speed and the corresponding bridge efficiency includes:

[0094] The corresponding relationship between vehicle gear, bridge efficiency and vehicle speed has corresponding shift points. When the vehicle speed is at the speed value corresponding to the shift point, the vehicle gear is adjusted.

[0095] Adjusting the vehicle's gear based on the current vehicle speed and the corresponding wheel torque includes:

[0096] The corresponding relationship between the vehicle gear, wheel torque and vehicle speed has a corresponding shift node. When the vehicle speed is at the speed value corresponding to the shift node, the vehicle gear is adjusted.

[0097] Among them, continue to refer to Figure 4 and Figure 5 When the vehicle speed continuously increases and reaches the shift point speed, such as 22 km / h, you can shift from first gear to second gear. Similarly, when the vehicle speed continuously decreases and reaches the shift point speed, you can shift from second gear to first gear. Figure 4 and Figure 5 Using only first and second gear as examples, other gears may be included in other embodiments.

[0098] Optionally, the multi-stage oil-cooled electric drive bridge system includes at least two electric drive bridges, and the method further includes:

[0099] The system retrieves the corresponding motor speed, wheel end torque, and motor torque relationships for each electric drive axle under the current coolant temperature and vehicle gear, and obtains the wheel end torque for different electric drive axles to calculate the total wheel end output torque of the vehicle.

[0100] The system retrieves the corresponding relationships between vehicle speed, wheel end torque, and overall axle efficiency for each electric drive axle under the current coolant temperature and vehicle gear. Based on the overall axle efficiency and total wheel end output torque for different electric drive axles, and under the condition of maximizing the sum of the overall axle efficiency of each electric drive axle, the system redistributes different wheel end torques to different electric drive axles.

[0101] The operation of each electric drive axle is controlled by the distributed wheel-end torque.

[0102] The electric drive axle can consist of two or more axles; the following explanation uses a two-axle axle as an example. For different electric drive axles, the corresponding motor speed, wheel-end torque, and motor torque under the current operating conditions are retrieved. This correspondence can be pre-calibrated. This yields the wheel-end torque for each different electric drive axle, thus obtaining the overall wheel-end torque of the vehicle. Then, based on the corresponding relationship between vehicle speed, wheel-end torque, and overall axle efficiency, the overall wheel-end torque of the vehicle is redistributed to optimize the overall axle efficiency.

[0103] It should be noted that, Figure 6 This is a schematic diagram showing the vehicle speed, wheel-end torque, and overall axle efficiency corresponding to a single axle in the efficiency improvement method for a multi-speed oil-cooled electric drive axle system proposed in an embodiment of the present invention; as shown. Figure 6 As shown, the horizontal axis represents vehicle speed, the vertical axis represents wheel-end torque, and the value on the curve represents the overall bridge efficiency.

[0104] At the dotted line (with the vehicle speed constant), it can be seen that as the wheel-end torque increases, the overall bridge efficiency first increases and then decreases (for example, from point B to point A).

[0105] If the current total wheel-end output torque, i.e. the required total wheel-end torque, is 1000 Nm, and the vehicle has two electric drive axles, with each axle having the same vehicle speed, wheel-end torque, and overall axle efficiency curves under the same operating conditions, then the following distribution method can be used:

[0106] Method 1: Axle 1 outputs a wheel end torque of 1000 Nm, and axle 2 does not work.

[0107] Method 2: Axle 1 outputs a wheel end torque of 500 Nm, and axle 2 outputs a wheel end torque of 500 Nm.

[0108] Method x: The output wheel end torque of bridge 1 is 1000×a Nm, where a ranges from 0 to 1. The output wheel end torque of bridge 2 is 1000×(1-a) Nm.

[0109] Under different allocation methods, the overall bridge efficiency of the entire system corresponding to each allocation method can be calculated, and the allocation method with the highest sum of overall bridge efficiencies is taken as the final allocation method.

[0110] If the system has more electric drive axles, the wheel-end torque can also be distributed in the manner described above, which will not be elaborated here.

[0111] In other words, in a specific embodiment, based on the overall axle efficiency and total wheel-end output torque corresponding to different electric drive axles, and under the condition that the sum of the overall axle efficiencies of each electric drive axle is maximized, the redistribution of different wheel-end torques to different electric drive axles includes:

[0112] If the total output torque at the wheel end is T, and the electric drive axle includes a first electric drive axle and a second electric drive axle, the torque allocated to the first electric drive axle is T×a, and the corresponding efficiency of the first electric drive axle is η(a), then the torque allocated to the second electric drive axle is T×(1-a), and the corresponding efficiency of the second electric drive axle is η(1-a).

[0113] Iterate through a from 0 to 1 to minimize T×a / η(a) + T×(1-a) / η(1-a) to satisfy the condition that the sum of the overall bridge efficiency of each electric drive bridge is maximized.

[0114] Optionally, controlling the operation of the electric drive axle with the distributed wheel-end torque includes:

[0115] After assigning different wheel-end torques to different electric drive axles, the wheel-end torques of different electric drive axles are linearly adjusted, while the motor torques associated with the corresponding electric drive axles are non-linearly adjusted.

[0116] Understandably, if the current wheel-end torque of axle 1 is 500 Nm, the wheel-end torque of axle 2 is 500 Nm, and the speed ratio is 10 (the motor rotates 10 times, and the wheel rotates 1 time; if the motor torque is 10 Nm, and losses are not considered, then based on the speed ratio, the wheel-end torque can be calculated to be 100 Nm), and according to the previous distribution method, it needs to be adjusted so that the wheel-end torque of axle 1 is 1000 Nm and the output torque of axle 2 is 0 Nm, then it is necessary to increase the wheel-end output torque of axle 1 and decrease the wheel-end output torque of axle 2. Furthermore, the increase in axle 1 should be matched by the decrease in axle 2 to ensure that the sum of the wheel-end torques of axle 1 and axle 2 remains unchanged.

[0117] Therefore, the wheel-end torque of axle 1 can be gradually changed from 500 Nm to 550 Nm, 600 Nm, 650 Nm...1000 Nm (linearly increasing). When the wheel-end torque of axle 1 increases from 500 Nm to 550 Nm, the motor torque may increase from 51 Nm to 56.2 Nm; when the wheel-end torque of axle 1 increases from 550 Nm to 600 Nm, the motor torque may increase from 56.2 Nm to 62.3 Nm. The increase in motor torque is non-linear. Similarly, in order to ensure that the wheel-end torque of axle 2 decreases linearly, the motor torque on axle 2 needs to decrease non-linearly.

[0118] in, Figure 7 This is a schematic diagram illustrating the relationship between the wheel end torque and motor torque of a single axle in the efficiency improvement method for a multi-speed oil-cooled electric drive axle system proposed in an embodiment of the present invention; as shown. Figure 7 As shown, when the wheel-end torque increases linearly, the motor torque increases non-linearly. This avoids fluctuations in the sum of wheel-end torques during torque distribution, which would affect the smooth operation of the vehicle.

[0119] Optionally, before determining the current operating condition of the vehicle, the following steps are also included:

[0120] Based on the motor calibration bench, the corresponding relationship between motor speed, motor torque and electronic control efficiency is calibrated;

[0121] Based on the bridge abutment, under given gear, motor speed, and motor torque, the corresponding multi-dimensional data correspondence between water pump flow rate, cooling lubricating oil temperature, wheel end torque, electric drive axle wheel end speed, electric drive axle wheel end output power, overall axle efficiency, electronic control temperature, motor temperature, and vehicle speed is calibrated.

[0122] First, the correspondence between motor speed, motor torque, and electronic control efficiency is calibrated. This involves controlling the DC input power of the motor to obtain the aforementioned values ​​sequentially, establishing the corresponding relationships. Then, under given gear, vehicle speed, motor speed, and motor torque, and while meeting the cooling requirements of the motor and motor controller, based on the following... Figure 1The system shown changes the water pump flow rate, collects the cooling oil temperature, measures the output of the wheel end torque, and combines this with the wheel end speed (or speed ratio) to calculate the wheel end output power, thereby obtaining the following multi-dimensional information: [gear, vehicle speed, motor torque, motor speed, water pump flow rate (and water pump losses at that flow rate), cooling oil temperature, wheel end torque, electronic control temperature, motor temperature, and overall axle efficiency (wheel end output power / motor DC input power)], forming an array of corresponding relationships.

[0123] Based on this multidimensional data, various correlations can be obtained. For example, given the motor torque, motor speed, and gear position, the optimal cooling oil temperature (which, according to the calibration multidimensional data table, yields the water pump flow rate at that temperature) results in the highest overall axle efficiency. Furthermore, given the gear position and cooling oil temperature, the correlations between "motor speed - wheel end torque - motor torque," "vehicle speed - wheel end torque - overall axle efficiency" (horizontal axis vehicle speed, vertical axis - wheel end torque, coordinate value - overall axle efficiency), and "vehicle speed - motor torque - overall axle efficiency," among other data, can be derived.

[0124] Because the calibration process uses measured values ​​for wheel-end torque (e.g., measured by torque sensors), calculates wheel-end output power based on these measured values, and calculates overall axle efficiency using both measured wheel-end output power and motor DC input power, while also considering the effects of cooling oil temperature and water pump flow rate, the calibration results are closer to the actual values. Compared to overall axle efficiency calculated solely based on motor speed, motor torque, and electronic control efficiency, the calibration results are more accurate. Consequently, using these calibration results to control the vehicle results in better overall axle efficiency.

[0125] Optionally, Figure 8 This is a schematic diagram of a multi-stage oil-cooled electric drive bridge system according to an embodiment of the present invention, as shown below. Figure 8 As shown, the water-cooling assembly includes a water pump 1061, a radiator 1062, and water channels;

[0126] The water pump 1061 is connected to the water outlet of the radiator 1062, the water outlet of the water pump 1061 is connected to the water inlet of the water channel in the motor controller 103, the water outlet of the water channel in the motor controller 103 is connected to the water inlet of the water channel in the motor 104, and the water outlet of the water channel in the motor 104 is connected to the water inlet of the radiator 1062.

[0127] The motor 104 is also equipped with a heat exchanger, which is connected to the oil cooling assembly 105 and the water channel in the motor 104 respectively.

[0128] The oil cooling assembly 105 includes a housing, cooling lubricating oil, and a temperature sensor 31. The housing contains a shift actuator 102 and cooling lubricating oil, and the temperature sensor 31 is used to measure the oil temperature of the cooling lubricating oil.

[0129] In this system, water pump 1061 pumps cooling water to motor controller 103, which then cools the controller before the water enters motor 104. The cooling water then passes through water channels in motor 104, carrying away heat from the motor itself and from the heat exchanger after exchanging heat with the lubricating oil. The water then enters radiator 1062, where it dissipates heat and becomes cooling water again, which is then circulated back to water pump 1061. This water circulation system cools the entire system and improves its overall efficiency.

[0130] It is understandable that the efficiency of the system is improved by accurately determining the shift points and / or the water pump flow rate and / or the reasonable torque distribution in different electric drive axles.

[0131] In summary, this invention provides a method for improving the efficiency of a multi-speed oil-cooled electric drive axle system. The multi-speed oil-cooled electric drive axle system includes: a transmission controller, a shift actuator and a motor controller connected to the transmission controller, a motor connected to the motor controller, an oil-cooling component, and a water-cooling component. The oil-cooling component cools the shift actuator, and the water-cooling component cools the oil-cooling component, the motor, and the motor controller. The method includes: determining the current operating condition of the vehicle, where operating parameters include the vehicle gear, motor speed, and motor torque; and invoking the correspondence between the overall axle efficiency calibrated under the current operating condition and the cooling oil temperature in the oil-cooling component. The system establishes a correlation between cooling oil temperature and water pump flow rate in the water-cooled components. It extracts the current cooling oil temperature and corresponding water pump flow rate at which the overall axle efficiency is highest under current operating conditions. The system controls the water-cooled components to operate at the current water pump flow rate and collects the cooling oil temperature of the oil-cooled components. Timing is then performed. Within a first preset time period, the water-cooled components are controlled to operate at the current water pump flow rate, with the current water pump flow rate increased by a first-step flow rate, and with the current water pump flow rate decreased by a first-step flow rate for the same duration. The first water pump flow rate corresponding to the highest overall efficiency is determined, and the water-cooled components are controlled to continue operating at this first flow rate. The overall efficiency is the sum of the overall axle efficiency and the water pump losses. Therefore, this electric drive axle system not only considers the overall axle efficiency in advance, operating when the overall axle efficiency is high, but also considers water pump losses during operation. By adjusting the water pump flow rate, it affects the cooling oil temperature, further influencing the overall axle efficiency. By comprehensively considering the impact of water pump losses on the overall axle efficiency, the electric drive axle system operates at a high overall efficiency, improving energy utilization and enhancing the driver experience.

[0132] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0133] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system, characterized in that, The multi-speed oil-cooled electric drive axle system includes: a gearbox controller, a shift actuator and a motor controller respectively connected to the gearbox controller, a motor connected to the motor controller, an oil cooling assembly and a water cooling assembly, wherein the oil cooling assembly is used to cool the shift actuator, and the water cooling assembly is used to cool the oil cooling assembly, the motor and the motor controller; The method includes: Determine the current operating condition of the vehicle, wherein the operating parameters under the current operating condition include the vehicle gear, motor speed and motor torque; The system calls upon the correspondence between the overall bridge efficiency calibrated under the current operating conditions and the cooling oil temperature in the oil-cooled assembly, as well as the correspondence between the cooling oil temperature and the water pump flow rate in the water-cooled assembly. Extract the current cooling oil temperature corresponding to the highest overall bridge efficiency under the current operating conditions, and the current water pump flow rate corresponding to the current cooling oil temperature; Control the water-cooling assembly to operate at the current water pump flow rate, and collect the cooling oil temperature of the oil-cooling assembly; and time the process; Within a first preset time period, the water-cooling component is controlled to run for the same amount of time at the current water pump flow rate, the current water pump flow rate plus the first step long flow rate, and the current water pump flow rate minus the first step long flow rate. The first water pump flow rate corresponding to the highest overall efficiency is determined, and the water-cooling component is controlled to continue running at the first water pump flow rate. The overall efficiency is the efficiency after adding the overall bridge efficiency to the water pump loss. If the flow rate of the first water pump is the current water pump flow rate, then the water cooling component is controlled to continue operating at the current water pump flow rate; If the first water pump flow rate is the value after increasing or decreasing the current water pump flow rate by a first step long flow rate, the method further includes: at a second preset time interval, continuing to adjust the first water pump flow rate by increasing or decreasing the first step long flow rate to the second water pump flow rate; and when the overall efficiency after adjustment is lower than before adjustment, controlling the water cooling component to continue operating with the first water pump flow rate, and when the overall efficiency after adjustment is higher than before adjustment, controlling the water cooling component to continue operating with the second water pump flow rate, and so on, until the current operating condition changes.

2. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 1, characterized in that, Control the water cooling assembly to operate at the current water pump flow rate, and collect the cooling oil temperature of the oil cooling assembly; After timing, it also includes: When the temperature of the cooling oil exceeds a preset threshold range, the water cooling component is controlled to operate at a preset flow rate fluctuating with the current water pump flow rate, and the search for the water pump flow rate corresponding to the highest overall efficiency is completed.

3. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 1, characterized in that, The operating parameters also include vehicle speed. After extracting the current cooling oil temperature corresponding to the highest overall bridge efficiency, the method further includes: The system retrieves the corresponding relationship between the vehicle gear, axle efficiency, and vehicle speed at the current cooling oil temperature, and adjusts the vehicle gear based on the vehicle speed under the current operating conditions and the axle efficiency corresponding to the vehicle speed. The axle efficiency is the ratio of wheel-end output power to motor DC input power. Alternatively, the corresponding relationship between vehicle gear, wheel torque, and vehicle speed at the current cooling oil temperature can be invoked, and the vehicle gear can be adjusted based on the vehicle speed under the current operating conditions and the wheel torque corresponding to the vehicle speed, wherein the wheel torque is obtained by actual measurement during calibration.

4. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 3, characterized in that, Adjusting the vehicle's gear based on the current vehicle speed and the corresponding bridge efficiency includes: The corresponding relationship between the vehicle gear, bridge efficiency and vehicle speed has a corresponding shift node. When the vehicle speed is at the speed value corresponding to the shift node, the vehicle gear is adjusted. Adjusting the vehicle's gear based on the current vehicle speed and the corresponding wheel torque includes: The corresponding relationship between the vehicle gear, wheel torque and vehicle speed has a corresponding shift node. When the vehicle speed is at the speed value corresponding to the shift node, the vehicle gear is adjusted.

5. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 1, characterized in that, The multi-stage oil-cooled electric drive bridge system includes at least two electric drive bridges, and the method further includes: By calling up the corresponding relationship between the motor speed, wheel end torque, and motor torque of each electric drive axle under the current cooling oil temperature and the vehicle's gear position, the wheel end torque of different electric drive axles is obtained to calculate the total wheel end output torque of the vehicle. The system retrieves the correspondence between the vehicle speed, wheel end torque, and overall axle efficiency of each electric drive axle under the current cooling oil temperature and the vehicle's gear position. Based on the overall axle efficiency and the total wheel end output torque corresponding to different electric drive axles, and under the condition that the sum of the overall axle efficiencies of each electric drive axle is maximized, the system redistributes different wheel end torques to different electric drive axles. The operation of each electric drive axle is controlled by the distributed wheel-end torque.

6. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 5, characterized in that, Based on the overall axle efficiency and the total wheel-end output torque corresponding to different electric drive axles, and under the condition that the sum of the overall axle efficiencies of each electric drive axle is maximized, the redistribution of different wheel-end torques to different electric drive axles includes: If the total output torque at the wheel end is T, and the electric drive axle includes a first electric drive axle and a second electric drive axle, and the torque allocated to the first electric drive axle is T×a, and the corresponding efficiency of the first electric drive axle is η(a), then the torque allocated to the second electric drive axle is T×(1-a), and the corresponding efficiency of the second electric drive axle is η(1-a). Iterate through a from 0 to 1 to minimize T×a / η(a) + T×(1-a) / η(1-a) to satisfy the condition that the sum of the overall bridge efficiency of each electric drive bridge is maximized.

7. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 5 or 6, characterized in that, Controlling the operation of each electric drive axle using the distributed wheel-end torque includes: After assigning different wheel-end torques to different electric drive axles, the wheel-end torques of different electric drive axles are linearly adjusted, and the motor torques associated with the corresponding electric drive axles are non-linearly adjusted.

8. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 1, characterized in that, Before determining the current operating condition of the vehicle, the following is also included: Based on the motor calibration bench, the corresponding relationship between motor speed, motor torque and electronic control efficiency is calibrated; Based on the bridge abutment, under given gear, motor speed, and motor torque, the corresponding multi-dimensional data correspondence between water pump flow rate, cooling lubricating oil temperature, wheel end torque, electric drive axle wheel end speed, electric drive axle wheel end output power, overall axle efficiency, electronic control temperature, motor temperature, and vehicle speed is calibrated.

9. The method for improving the efficiency of a multi-stage oil-cooled electric drive bridge system according to claim 1, characterized in that, The water-cooling assembly includes a water pump, a radiator, and water channels; The water pump inlet is connected to the radiator outlet, the water pump outlet is connected to the water inlet of the water channel in the motor controller, the water channel outlet in the motor controller is connected to the water inlet of the water channel in the motor, and the water channel outlet in the motor is connected to the radiator inlet. The motor is also equipped with a heat exchanger, which is connected to the oil cooling assembly and the water channel in the motor respectively; The oil cooling assembly includes a housing, cooling lubricating oil, and a temperature sensor. The housing contains a shift actuator and the cooling lubricating oil, and the temperature sensor is used to measure the oil temperature of the cooling lubricating oil.

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