A hybrid transmission electronic control system overcurrent protection method

Abstract

The present invention discloses an overcurrent protection method for a hybrid transmission electronic control system, belonging to the field of hybrid transmission electronic control system control technology. Under the premise of ensuring the minimum lubrication flow of the cooling and lubrication system, the CLPM current under the minimum lubrication state is calculated, and then the maximum current available to the CAPM at this time is obtained based on the maximum current limit of the bus circuit. Subsequently, based on the maximum power output of the CAPM under the current operating voltage, the maximum allowable oil pressure of the clutch is calculated, and finally the maximum torque that the clutch can transmit under the current working condition is calculated; according to the bus current exceeding different limit values, based on the current target or actual cooling and lubrication flow rate, the cooling and lubrication flow rate limit values ​​under different situations are calculated respectively, until the final target cooling and lubrication flow rate is reduced to the minimum lubrication flow rate. Based on the maximum bus current limit, the present invention limits the bus current by rationally distributing the workload of the two BLDC motors to prevent bus overcurrent.

Description

Technical Field

[0001] The present invention belongs to the technical field of hybrid transmission electronic control system control, and more specifically, relates to an overcurrent protection method for a hybrid transmission electronic control system. Background Art

[0002] Based on a self-developed hybrid transmission, an electronic pump driven by two BLDC motors is used to control the clutch and cooling lubrication respectively, thereby realizing the series-parallel switching of the hybrid mode and the cooling of the power motor and the lubrication of the transmission shaft gear. Among them, the HTCU calculates the clutch target pressure and the clutch oil pump motor (CAPM) target duty cycle according to the clutch target transmission torque issued by the vehicle controller. At the same time, it calculates the target cooling lubrication flow and the cooling lubrication oil pump motor (CLPM) target duty cycle according to the power motor temperature, speed and transmission oil temperature of the hybrid electric drive assembly. Both use PWM control to drive the clutch electronic pump and the cooling lubrication electronic pump respectively according to the calculated target duty cycle. The schematic diagram of the BLDC motor drive circuit inside the HTCU is as follows: Figure 1 As shown, the HTCU receives power from the battery and distributes it through the bus circuit to supply power to two BLDC motors respectively, that is, the bus current is the sum of the CAPM current and the CLPM current.

[0003] When the workload of the hybrid transmission's CAPM and CLPM is very heavy, the bus current will be too large. The HTCU underlying software will enable the overcurrent protection function and directly shut down the two BLDC motors. In this way, the clutch torque transmission and system cooling and lubrication will be interrupted, making it impossible for the hybrid electric drive assembly to enter the series working mode and unable to obtain cooling and lubrication, which will eventually cause the vehicle to be unable to drive normally. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention proposes an overcurrent protection method for a hybrid transmission electronic control system. The control strategies of CAPM and CLPM need to be optimized by the HTCU application layer software. Based on the maximum limit of the bus current, the bus current is limited by reasonably distributing the workload of the two BLDC motors to prevent bus overcurrent.

[0005] To achieve the above objectives, the present invention provides an overcurrent protection method for an electronic control system of a hybrid transmission, comprising:

[0006] (1) Under the premise of ensuring the minimum lubrication flow of the cooling and lubrication system, the CLPM current under the minimum lubrication state is calculated. Then, the maximum current available to the CAPM at this time is obtained based on the maximum current limit of the bus circuit. Then, based on the maximum power output of the CAPM under the current working voltage, the maximum allowable oil pressure of the clutch is calculated. Finally, the maximum torque that can be transmitted by the clutch under the current working condition is calculated, thereby limiting the workload of the CAPM.

[0007] (2) According to the bus current exceeding different limit values, based on the current target or actual cooling and lubrication flow rate, the cooling and lubrication flow rate limit values ​​under different situations are calculated respectively until the final target cooling and lubrication flow rate is reduced to the minimum lubrication flow rate, thereby reducing the CLPM workload.

[0008] In some optional embodiments, step (1) comprises:

[0009] (1.1) When the preset conditions are met, the minimum lubrication flow rate of the cooling lubrication system is calculated, where the minimum lubrication flow rate is a one-dimensional function table related to the gearbox oil temperature;

[0010] (1.2) Calculate the CLPM working current corresponding to the minimum lubrication flow rate, store it as the minimum lubrication current, and update the minimum lubrication current value in different subsystems;

[0011] (1.3) Calculate the maximum allowable current of the CAPM motor, where the maximum allowable current of the CAPM is the difference between the maximum bus current limit and the estimated minimum lubrication current;

[0012] (1.4) Estimate the current maximum available power of the CAPM based on the maximum allowable current of the CAPM and the current system power supply voltage. Also, obtain the maximum allowable oil pressure of the CAPM based on the ratio of the current oil pressure to the current CAPM motor power.

[0013] (1.5) Based on the calculated maximum allowable CAPM oil pressure and oil pressure-torque coefficient, the maximum transmittable torque of the clutch is obtained, thereby limiting the maximum workload of the CAPM motor.

[0014] In some optional implementation schemes, the preset condition is to satisfy at least one of the following conditions:

[0015] The generator speed is greater than the minimum lubrication speed of the generator, or the drive motor speed is greater than the minimum lubrication speed of the generator; or, after power-on, the minimum lubrication flow is output within the preset time; or, when the oil temperature sensor fails, the minimum lubrication flow is executed.

[0016] In some optional embodiments, step (1.2) includes:

[0017] (1.2.1) The first subsystem has no lubrication requirement, wherein the trigger condition of the first subsystem is that the minimum lubrication flow is 0, and the output of the first subsystem is that the minimum lubrication current is 0;

[0018] (1.2.2) The second subsystem is for setting a new minimum lubrication value. The triggering condition for the second subsystem is: if the minimum lubrication flow rate changes and the change is greater than the flow change of the set new minimum lubrication current, or if the oil temperature changes and the change is greater than the oil temperature change of the set new minimum lubrication current;

[0019] (1.2.3) The third subsystem is in the minimum lubrication state. The triggering condition of the third subsystem is: the current minimum lubrication flow is the same as the current actual cooling lubrication flow or the difference between the two is less than the preset minimum lubrication flow error;

[0020] (1.2.4) The fourth subsystem is not in the minimum lubrication state. The triggering condition of the fourth subsystem is: the current actual cooling lubrication flow rate is greater than the minimum lubrication flow rate.

[0021] In some optional embodiments, step (1.2.2) includes:

[0022] If the current minimum lubrication flow rate increases and exceeds the stored minimum lubrication flow rate by the amount of flow change of the set new minimum lubrication current, the minimum lubrication current remains unchanged, that is, the last stored minimum lubrication current is continued to be used; if the current minimum lubrication flow rate decreases and falls below the stored minimum lubrication flow rate by the amount of flow change of the set new minimum lubrication current, the stored minimum lubrication current needs to be reset to recalculate the minimum lubrication current;

[0023] If the difference between the current oil temperature and the stored minimum lubricating oil temperature exceeds the oil temperature change required for the set new minimum lubricating current, the stored minimum lubricating current will be reduced to 0 according to the preset descending slope, and then the minimum lubricating current will be recalculated and stored under the current working conditions.

[0024] The current minimum lubrication flow rate is stored as a minimum lubrication flow rate estimate, and the current oil temperature is also stored as a minimum lubrication oil temperature estimate.

[0025] In some optional embodiments, step (1.2.3) includes:

[0026] In the minimum lubrication state, if the stored minimum lubrication current is smaller than the current CLPM current, the minimum lubrication current shall be increased to the actual CLPM current value at the preset minimum lubrication current increase rate based on the stored minimum lubrication current;

[0027] If the stored minimum lubrication current is greater than the current CLPM current, the minimum lubrication current should decrease to the actual CLPM current value at the minimum lubrication current decrease rate based on the stored minimum lubrication current;

[0028] If the current CLPM current is equal to or exceeds the stored minimum lubrication current, the minimum lubrication flow estimate needs to be updated to the current minimum lubrication flow; otherwise, the minimum lubrication flow estimate remains unchanged.

[0029] If the current oil temperature is equal to or exceeds the stored minimum lubricating oil temperature, the estimated minimum lubricating oil temperature needs to be updated to the current minimum lubricating oil temperature; otherwise, the estimated minimum lubricating oil temperature remains unchanged.

[0030] In some optional embodiments, step (1.2.4) includes:

[0031] If the actual cooling lubrication flow rate is greater than the stored minimum lubrication flow rate but the current CLPM actual current is less than the stored minimum lubrication current, the stored minimum lubrication current is decreased at a preset minimum lubrication current decrease rate until it is equal to the current CLPM actual current to update the minimum lubrication current;

[0032] If the actual cooling and lubrication flow rate is less than the stored minimum lubrication flow rate or the current CLPM actual current is greater than the stored minimum lubrication current, the minimum lubrication current continues to be the stored minimum lubrication current and remains unchanged, allowing the CAPM operating current to increase. If the CAPM workload increases and the bus current increases to even the overcurrent limit, the CLP cooling and lubrication flow rate will be reduced, reducing the CLPM workload and the CLPM operating current to avoid bus overcurrent.

[0033] In some optional embodiments, step (2) includes:

[0034] (2.1) If the bus current is greater than the first bus current limit, the cooling and lubrication flow rate limit remains the cooling and lubrication flow rate limit of the previous operation cycle, wherein the initial value of the cooling and lubrication flow rate limit is the maximum flow rate of the cooling and lubrication system and is determined according to the actual cooling and lubrication system demand;

[0035] (2.2) Calculate the cooling and lubrication flow limit when the bus current exceeds the second bus current limit;

[0036] (2.3) After the bus current is lower than the first bus current limit, the cooling and lubrication flow limit increases at the preset CLPM overcurrent increase rate and returns to the maximum flow of the cooling and lubrication system;

[0037] (2.4) The final cooling and lubrication flow limit after over-current limitation is the larger of the cooling and lubrication flow limit calculated in steps (2.1) to (2.3) and the minimum lubrication flow.

[0038] In some optional embodiments, step (2.2) includes:

[0039] If the bus current is greater than the second bus current limit, the cooling and lubrication flow limit is reduced based on the cooling and lubrication flow limit of the previous operation cycle at the preset CLPM overcurrent reduction rate;

[0040] When the bus current drops below the second bus current limit but is still higher than the first bus current limit, the cooling and lubrication flow limit continues to decrease at the preset CLPM overcurrent decrease rate based on the cooling and lubrication flow limit of the previous operating cycle, and ultimately the cooling and lubrication flow limit cannot exceed the current actual or target cooling and lubrication flow.

[0041] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0042] Through a detailed and rational overcurrent protection strategy design, the BLDC motor can be effectively protected from overcurrent, while ensuring the normal operation of the hybrid electric drive system, thereby improving the reliability of the HTCU electronic control system. Furthermore, this strategy can be implemented solely through optimization of the HTCU application layer software, without requiring any changes to the underlying HTCU motor driver, HTCU hardware, or BLDC motor hardware, resulting in high efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the principle of an HTCU BLDC motor drive circuit provided by an embodiment of the present invention;

[0044] Figure 2 This is a flow chart of an overcurrent protection method for a hybrid transmission electronic control system provided by an embodiment of the present invention;

[0045] Figure 3 This is a minimum lubrication state entry condition logic block diagram provided by an embodiment of the present invention;

[0046] Figure 4 This is a logic block diagram for calculating the minimum lubrication value in the second subsystem provided by an embodiment of the present invention;

[0047] Figure 5 This is a logic block diagram for calculating the minimum lubrication value in the third subsystem provided by an embodiment of the present invention;

[0048] Figure 6 This is a logic block diagram for calculating the minimum lubrication value in a fourth subsystem provided by an embodiment of the present invention;

[0049] Figure 7 This is an overall block diagram of the minimum lubrication current calculation logic provided by an embodiment of the present invention;

[0050] Figure 8 This is a logic block diagram for calculating the maximum allowable oil pressure of a CAP provided by an embodiment of the present invention;

[0051] Figure 9 This is a logic block diagram for calculating the maximum transmittable torque of a clutch provided by an embodiment of the present invention;

[0052] Figure 10 This is a CLPM workload limit calculation logic block diagram provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0054] In the examples of the present invention, “first”, “second”, etc. are used to distinguish different objects rather than to describe a specific order or sequence.

[0055] In the embodiment of the present invention, HTCU: Hybrid Transmission Control Unit; BLDC: Brushless Direct Current; CAPM: Clutch Actuator Pump Motor; CLPM: Cooling Lubrication Pump Motor.

[0056] In this invention, the normal operation of the hybrid electric drive system prioritizes the proper functioning of the CAPM over nominal cooling and lubrication. However, when the electric drive system is operating, at least basic shaft and gear lubrication (i.e., minimum lubrication) must be maintained. Based on this design, the HTCU application-layer software control strategy reduces the CLPM workload by reducing the cooling and lubrication flow rate to the minimum lubrication flow rate before a busbar current overcurrent event occurs. This also reduces the CAPM workload by limiting or reducing the clutch torque capacity, ultimately preventing busbar overcurrent.

[0057] The present invention provides a hybrid transmission electronic control system overcurrent protection method, such as Figure 2As shown, it includes: under the premise of ensuring the minimum lubrication flow of the cooling and lubrication system, calculating the CLPM current under the minimum lubrication state, and then based on the maximum current limit of the bus circuit, the maximum current available to the CAPM at this time can be obtained, and then based on the maximum power that the CAPM can output under the current working voltage, the maximum allowable oil pressure of the clutch is further calculated, and finally the maximum torque that the clutch can transmit under the current working condition is calculated, thereby limiting the CAPM workload. At the same time, according to the bus current exceeding different limits, based on the current target or actual cooling and lubrication flow, the cooling and lubrication flow limit values ​​under different situations are calculated respectively, until the final target cooling and lubrication flow is reduced to the minimum lubrication flow, thereby reducing the CLPM workload. In summary, by jointly limiting the workloads of both CAPM and CLPM, overcurrent of the drive circuit bus is avoided.

[0058] In the present invention, the CAPM workload limit strategy design and calculation steps are as follows:

[0059] Step 1 Calculate the minimum lubrication flow of the cooling lubrication system:

[0060] The minimum lubrication flow is designed as a one-dimensional function table related to the transmission oil temperature. The corresponding minimum lubrication flow is obtained by looking up the table based on the current transmission oil temperature. To ensure that the minimum lubrication flow matches the actual system requirements and consider the versatility of the software module, the one-dimensional function table data is calibrable. However, considering the actual operating conditions of the electric drive assembly, minimum lubrication is not required under all conditions. At least one of the following conditions must be met:

[0061] (1) The generator speed is greater than the minimum lubrication speed of the generator, or the drive motor speed is greater than the minimum lubrication speed of the generator; the speed value can be calibrated, such as 10 rpm;

[0062] (2) Even before the electric drive assembly gear train is working, a certain initial lubrication flow is required to complete the oil filling, that is, after power is turned on, the minimum lubrication flow is output within the preset time, and the time can be calibrated according to the actual situation, such as 5s;

[0063] (3) Since the calculation of the target cooling and lubrication flow is mainly based on the oil temperature and the difference between the oil temperature and the power motor temperature, when the oil temperature sensor fails, the calculated target cooling and lubrication flow is inaccurate. To ensure the safety of the system, the minimum lubrication flow is used.

[0064] The design of the minimum lubrication calculation logic block diagram is as follows Figure 3 To help understand and illustrate the strategic design ideas of this solution, and in combination with the actual working requirements of the electric drive assembly, the oil temperature-minimum lubrication flow rate initially set in the following table is taken as an example:

[0065] Table 1

[0066] Oil temperature / ℃ -30 -11 -10 -6 -5 19 20 140 Minimum lubrication flow rate / (L / min) 0.2 0.2 0.35 0.35 0.45 0.45 2 2

[0067] Step 2 calculates the CLPM working current corresponding to the minimum lubrication flow, that is, the minimum lubrication current:

[0068] In reality, it's difficult to determine the minimum lubrication current under all operating conditions except when the system is in the minimum lubrication state. Therefore, it's necessary to store the minimum lubrication current calculated under the minimum lubrication state and then update the stored minimum lubrication current value in a specific manner under different subsystems. This solution designs the following four subsystems:

[0069] 1) First subsystem: no lubrication requirement;

[0070] The system does not require lubrication at this time.

[0071] System triggering conditions: minimum lubrication flow = 0;

[0072] System output: minimum lubrication current = 0;

[0073] 2) Second subsystem: Setting a new minimum lubrication value:

[0074] System triggering conditions: If the minimum lubrication flow changes and the change is greater than the flow change of the set new minimum lubrication current, or the oil temperature changes and the change is greater than the oil temperature change of the set new minimum lubrication current, the second subsystem will be triggered. At the same time, these changes are calibrated based on the calibrated minimum lubrication flow table and the actual performance of the cooling lubrication system.

[0075] Judgment and calculation logic in the second subsystem: Case 1: If the minimum lubrication flow increases and the flow change exceeds the stored minimum lubrication flow by more than the set new minimum lubrication current, the minimum lubrication current remains unchanged, that is, the last stored minimum lubrication current continues to be used. The corresponding working conditions are: the flow difference threshold is calibrated to 0.5L / min, the current minimum lubrication flow is 2L / min, and the stored minimum lubrication flow is 0.45L / min. The actual oil temperature must have increased during this process, so the oil viscosity decreases, the oil resistance to the cooling lubrication oil pump decreases, the CLPM load decreases, and the current consumed also decreases. As the oil temperature continues to rise, the minimum lubrication current should also decrease. At this time, the minimum lubrication current takes the minimum lubrication current value corresponding to the stored minimum lubrication flow estimate of 0.45L / min. Conversely, if the minimum lubrication flow rate decreases and is lower than the stored minimum lubrication flow rate by the amount of flow change required to set the new minimum lubrication current, the stored minimum lubrication current must be reset to recalculate the minimum lubrication current. This corresponds to the following operating conditions: the flow difference calibration value remains at 0.5 L / min, the current minimum lubrication flow rate is 0.45 L / min, and the stored minimum lubrication flow rate is 2 L / min. Scenario 2: The difference between the current oil temperature and the stored minimum lubrication oil temperature exceeds the amount of oil temperature change required to set the new minimum lubrication current (e.g., 5°C), indicating a significant change in the system operating conditions. The stored minimum lubrication current must be reduced to 0 according to the preset decreasing slope, and the minimum lubrication current must then be recalculated and stored for the current operating conditions. Furthermore, in both of these scenarios, the current minimum lubrication flow rate is stored as the estimated minimum lubrication flow rate. Similarly, the current oil temperature is also stored as the estimated minimum lubrication oil temperature. (Note: The estimated minimum lubrication flow rate is an intermediate variable introduced to calculate the minimum lubrication current, rather than the minimum lubrication flow rate calculated based on the oil temperature as defined above. Similarly, the estimated minimum lubrication oil temperature is also an intermediate variable introduced to calculate the minimum lubrication current, rather than the oil temperature corresponding to the current minimum lubrication flow rate or the current oil temperature.) The calculation logic block diagram is designed as follows Figure 4 shown.

[0076] 3) The third subsystem: in the minimum lubrication state;

[0077] System triggering condition: When the current minimum lubrication flow is the same as the current actual cooling lubrication flow or the difference between the two is less than the preset minimum lubrication flow error (a smaller value that can be calibrated), enter the system.

[0078] Judgment and calculation logic in the third subsystem: When in the minimum lubrication state, the minimum lubrication current is the actual CLPM current, but considering that the actual current will not change suddenly, the specific analysis is as follows: If the stored minimum lubrication current is smaller than the current CLPM current, the minimum lubrication current should be based on the stored minimum lubrication current and rise to the actual CLPM current value at the preset minimum lubrication current rise rate; conversely, if the stored minimum lubrication current is larger than the current CLPM current, the minimum lubrication current should be based on the stored minimum lubrication current and fall to the actual CLPM current value at the minimum lubrication current fall rate. Among them, the minimum lubrication current change rate needs to be calibrated according to the actual CLPM operating conditions. Similarly, when entering the system, if the current CLPM current is equal to or exceeds the stored minimum lubrication current, the minimum lubrication flow estimate needs to be updated to the current minimum lubrication flow. Otherwise, the minimum lubrication flow estimate remains unchanged. Similarly, the same is true for the minimum lubricating oil temperature estimate. The calculation logic block diagram is designed as follows Figure 5 shown.

[0079] 4) The fourth subsystem: not in minimum lubrication:

[0080] System triggering conditions: None of the above three system triggering conditions are met, that is, the current actual cooling and lubrication flow rate is greater than the minimum lubrication flow rate.

[0081] Judgment and calculation logic within the fourth subsystem: Two situations need to be considered. Situation 1: The actual cooling and lubrication flow is greater than the stored minimum lubrication flow, but the current CLPM actual current is less than the stored minimum lubrication current. In order to avoid sudden changes in the calculated current, the current CLPM current is not directly assigned to the minimum lubrication current. Instead, the stored minimum lubrication current is reduced at a preset minimum lubrication current decrease rate to be equal to the current CLPM actual current to update the minimum lubrication current. This situation is generally when the oil temperature rises and the CLPM current consumption decreases. Reducing the minimum lubrication current can increase the current available to the CAPM. Situation 2: The actual cooling and lubrication flow is less than the stored minimum lubrication flow or the current CLPM actual current is greater than the stored minimum lubrication current. The minimum lubrication current continues to take the stored minimum lubrication current and remains unchanged. In this case, the CAPM operating current can be allowed to increase. If the CAPM workload increases and the bus current increases or even reaches the overcurrent limit, the CLP cooling and lubrication flow will be reduced, reducing the CLPM workload, reducing the CLPM operating current, and avoiding bus overcurrent. The calculation logic block diagram is designed as follows Figure 6 shown.

[0082] The overall logical framework for calculating the minimum lubrication current of the above four subsystems is as follows: Figure 7 shown.

[0083] Step 3 Calculate the maximum allowable current of the CAPM motor

[0084] The maximum allowable current of CAPM is the difference between the maximum bus current limit and the estimated minimum lubrication current, where the maximum bus current limit depends on the HTCU hardware circuit and the underlying software overcurrent protection strategy.

[0085] Step 4 Calculate the maximum allowable oil pressure of CAP

[0086] The maximum allowable oil pressure of the CAPM is calculated based on the idea of ​​busbar available power limitation under the current working conditions. That is, the maximum allowable current of the CAPM and the current system power supply voltage are used to estimate the current maximum available power of the CAPM. At the same time, the maximum allowable oil pressure of the CAP can be finally obtained based on the ratio of the current oil pressure to the current CAPM motor power. The calculation logic block diagram is designed as follows: Figure 8 shown.

[0087] Step 5: Calculate the maximum transmittable torque of the clutch

[0088] Based on the calculated maximum allowable oil pressure and oil pressure-torque coefficient of the CAPM, the maximum torque that the clutch can transmit can be obtained, thereby limiting the maximum working load of the CAPM motor and ultimately preventing the CAPM from overloading and causing overcurrent. The calculation logic block diagram is designed as follows: Figure 9 shown.

[0089] The design and calculation steps of the CLPM workload limit strategy are as follows:

[0090] Step 1 Calculate the cooling and lubrication flow limit when the bus current exceeds the first limit

[0091] When the bus current is greater than the first bus current limit, the cooling and lubrication flow limit maintains the cooling and lubrication flow limit of the previous operation cycle. The initial value of the cooling and lubrication flow limit is the maximum flow of the cooling and lubrication system and is determined according to the actual cooling and lubrication system requirements. The first bus current limit can be determined according to the actual operating limitations of the HTCU hardware and CLPM. For example, if the maximum bus current limit is 30A, the first bus current limit can be 26A.

[0092] Step 2 calculates the cooling and lubrication flow limit when the bus current exceeds the second bus current limit;

[0093] When the bus current exceeds the second bus current limit (using 29A as an example), the cooling and lubrication flow rate limit should decrease based on the cooling and lubrication flow rate limit of the previous operating cycle at the preset CLPM overcurrent reduction rate. If the bus current exceeds the second bus current limit and then drops below the second bus current limit but still exceeds the first bus current limit due to a decrease in CLPM or CAPM workload, the cooling and lubrication flow rate limit will continue to decrease at the same rate based on the cooling and lubrication flow rate limit of the previous operating cycle. The final cooling and lubrication flow rate limit cannot exceed the current actual or target cooling and lubrication flow rate. (The target cooling and lubrication flow rate depends on the motor power, oil temperature, and motor speed. The initial target cooling and lubrication flow rate calculation can refer to existing technologies.)

[0094] Step 3 calculates the cooling and lubrication flow limit after the bus current is lower than the first bus current limit;

[0095] When the bus current drops below the first bus current limit, the cooling and lubrication flow limit should increase at the preset CLPM overcurrent rise rate and return to the maximum flow of the cooling and lubrication system, so that the cooling and lubrication demand during normal operation is not affected.

[0096] Step 4 calculates the final cooling and lubrication flow limit after over-current limitation.

[0097] The final cooling and lubrication flow limit after overcurrent limitation is the larger of the cooling and lubrication flow limit calculated in step 1 to step 3 and the minimum lubrication flow. This ensures that CLPM can provide minimum lubrication even when it is under overcurrent limitation. The above calculation steps and logic block diagram are shown in the figure. Figure 10 shown.

[0098] Through the above-mentioned technical solution, the present invention, from a system perspective, fully considers the system's operational requirements and operating conditions, interrelates the CAPM and CLPM operating conditions, rationally allocates bus current, and comprehensively designs the calculation logic for overcurrent protection of the electronic control system. To calculate the CAPM workload limit, four subsystems are designed based on the actual operating conditions of the cooling and lubrication system. Within each subsystem, the changes in the actual cooling and lubrication system parameters are analyzed in detail to calculate the minimum lubrication current value. This limits the maximum allowable CAPM workload while ensuring basic lubrication of the hybrid electric drive assembly. To calculate the CLPM workload limit, three different cooling and lubrication flow rate limits are designed based on different bus overcurrent conditions. When the bus current exceeds a certain overcurrent limit, the cooling and lubrication system is restricted to a minimum lubrication state at a calibrable CLPM overcurrent drop rate, reducing the CLPM workload. When the bus current returns to normal, the cooling and lubrication system restrictions are lifted at a calibrable CLPM overcurrent rise rate, allowing system operation to return to normal.

[0099] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

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

Claims

1. A hybrid transmission electronic control system overcurrent protection method, characterized in that: include: (1) Under the premise of ensuring the minimum lubrication flow of the cooling and lubricating system, the current of the cooling and lubricating oil pump motor (CLPM) under the minimum lubrication state is calculated. Then, based on the maximum current limit of the bus circuit, the maximum current available to the clutch oil pump motor (CAPM) at this time is obtained. Then, based on the maximum power output of the CAPM under the current working voltage, the maximum allowable oil pressure of the clutch is calculated. Finally, the maximum torque that can be transmitted by the clutch under the current working condition is calculated, thereby limiting the workload of the CAPM. (2) According to the bus current exceeding different limit values, based on the current target or actual cooling and lubrication flow rate, the cooling and lubrication flow rate limit values ​​under different situations are calculated respectively until the final target cooling and lubrication flow rate is reduced to the minimum lubrication flow rate, thereby reducing the CLPM workload.

2. The method according to claim 1, characterized in that Step (1) includes: (1.1) When the preset conditions are met, calculate the minimum lubrication flow rate of the cooling lubrication system, where the minimum lubrication flow rate is a one-dimensional function table related to the transmission oil temperature; (1.2) Calculate the CLPM operating current corresponding to the minimum lubrication flow rate, store it as the minimum lubrication current, and update the minimum lubrication current value in different subsystems; (1.3) Calculate the maximum allowable current of the CAPM motor, where the maximum allowable current of the CAPM is the difference between the maximum bus current limit and the estimated minimum lubrication current. (1.4) Estimate the current maximum available power of the CAPM using the maximum allowable current of the CAPM and the current system supply voltage. Also, calculate the maximum allowable oil pressure of the CAPM based on the ratio of the current oil pressure to the current CAPM motor power. (1.5) Based on the calculated maximum allowable CAPM oil pressure and oil pressure-torque coefficient, the maximum transmittable torque of the clutch is obtained, thereby limiting the maximum workload of the CAPM motor.

3. The method according to claim 2, characterized in that The preset condition is that at least one of the following conditions is met: The generator speed is greater than the minimum lubrication speed of the generator, or the drive motor speed is greater than the minimum lubrication speed of the generator; or, after power-on, the minimum lubrication flow is output within the preset time; or, when the oil temperature sensor fails, the minimum lubrication flow is executed.

4. The method according to claim 2 or 3, characterized in that Step (1.2) includes: (1.2.1) The first subsystem has no lubrication requirement, where the trigger condition for the first subsystem is that the minimum lubrication flow is 0, and the output of the first subsystem is that the minimum lubrication current is 0; (1.2.2) The second subsystem is for setting a new minimum lubrication value. The triggering conditions for the second subsystem are: if the minimum lubrication flow rate changes and the change is greater than the flow change of the set new minimum lubrication current, or if the oil temperature changes and the change is greater than the oil temperature change of the set new minimum lubrication current; (1.2.3) The third subsystem is in the minimum lubrication state. The triggering condition for the third subsystem is: the current minimum lubrication flow is the same as the current actual cooling lubrication flow or the difference between the two is less than the preset minimum lubrication flow error; (1.2.4) The fourth subsystem is not in the minimum lubrication state. The triggering condition of the fourth subsystem is: the current actual cooling lubrication flow is greater than the minimum lubrication flow.

5. The method according to claim 4, characterized in that Step (1.2.2) includes: If the current minimum lubrication flow rate increases and exceeds the stored minimum lubrication flow rate by the amount of flow change of the set new minimum lubrication current, the minimum lubrication current remains unchanged, that is, the last stored minimum lubrication current is continued to be used; if the current minimum lubrication flow rate decreases and falls below the stored minimum lubrication flow rate by the amount of flow change of the set new minimum lubrication current, the stored minimum lubrication current needs to be reset to recalculate the minimum lubrication current; If the difference between the current oil temperature and the stored minimum lubricating oil temperature exceeds the oil temperature change required for the set new minimum lubricating current, the stored minimum lubricating current will be reduced to 0 according to the preset descending slope, and then the minimum lubricating current will be recalculated and stored under the current working conditions. The current minimum lubrication flow rate is stored as a minimum lubrication flow rate estimate, and the current oil temperature is also stored as a minimum lubrication oil temperature estimate.

6. The method according to claim 5, characterized in that Step (1.2.3) includes: In the minimum lubrication state, if the stored minimum lubrication current is smaller than the current CLPM current, the minimum lubrication current shall be increased to the actual CLPM current value at the preset minimum lubrication current increase rate based on the stored minimum lubrication current; If the stored minimum lubrication current is greater than the current CLPM current, the minimum lubrication current should decrease to the actual CLPM current value at the minimum lubrication current decrease rate based on the stored minimum lubrication current; If the current CLPM current is equal to or exceeds the stored minimum lubrication current, the minimum lubrication flow estimate needs to be updated to the current minimum lubrication flow; otherwise, the minimum lubrication flow estimate remains unchanged. If the current oil temperature is equal to or exceeds the stored minimum lubricating oil temperature, the estimated minimum lubricating oil temperature needs to be updated to the current minimum lubricating oil temperature; otherwise, the estimated minimum lubricating oil temperature remains unchanged.

7. The method according to claim 6, characterized in that Step (1.2.4) includes: If the actual cooling lubrication flow rate is greater than the stored minimum lubrication flow rate but the current CLPM actual current is less than the stored minimum lubrication current, the stored minimum lubrication current is decreased at a preset minimum lubrication current decrease rate until it is equal to the current CLPM actual current to update the minimum lubrication current; If the actual cooling and lubrication flow rate is less than the stored minimum lubrication flow rate or the current CLPM actual current is greater than the stored minimum lubrication current, the minimum lubrication current continues to be the stored minimum lubrication current and remains unchanged, allowing the CAPM operating current to increase. If the CAPM workload increases and the bus current increases or even reaches the overcurrent limit, the CLPM cooling and lubrication flow rate will be reduced to reduce the CLPM workload, reduce the CLPM operating current, and avoid bus overcurrent.

8. The method according to claim 1, characterized in that Step (2) includes: (2.1) If the bus current is greater than the first bus current limit, the cooling and lubrication flow limit remains at the cooling and lubrication flow limit of the previous operating cycle, where the initial value of the cooling and lubrication flow limit is the maximum flow of the cooling and lubrication system and is determined based on the actual cooling and lubrication system requirements; (2.2) Calculate the cooling and lubrication flow limit when the bus current exceeds the second bus current limit; (2.3) After the bus current falls below the first bus current limit, the cooling and lubrication flow limit increases at the preset CLPM overcurrent rise rate and returns to the maximum flow of the cooling and lubrication system; (2.4) The final cooling and lubrication flow limit after over-current limitation is the larger of the cooling and lubrication flow limit calculated in steps (2.1) to (2.3) and the minimum lubrication flow.

9. The method according to claim 8, characterized in that Step (2.2) includes: If the bus current is greater than the second bus current limit, the cooling and lubrication flow limit is reduced based on the cooling and lubrication flow limit of the previous operation cycle at the preset CLPM overcurrent reduction rate; When the bus current drops below the second bus current limit but is still higher than the first bus current limit, the cooling and lubrication flow limit continues to decrease at the preset CLPM overcurrent decrease rate based on the cooling and lubrication flow limit of the previous operating cycle, and ultimately the cooling and lubrication flow limit cannot exceed the current actual or target cooling and lubrication flow.

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