Oil-cooling electric drive cooling oil distribution method and system and vehicle

Abstract

The invention discloses an oil cooling electric drive cooling oil distribution method and system and a vehicle, and the method comprises the steps that three cooling oil channels are distributed to a stator, a rotor and a speed reducer through an oil pump, and the cooling oil channels of the stator and the rotor are provided with a first valve and a second valve which are adjustable in flow respectively; estimating the real-time temperature of the rotor according to the actually detected real-time temperatures of the stator and the rotor and the acquired comprehensive working condition information of the electric drive system in combination with a temperature estimation algorithm, and obtaining the deviation between the real-time temperature and the preset temperature; inputting the deviation and the deviation change rate into a fuzzy PI controller to generate a dynamic flow control quantity; preferentially adjusting the opening degree of the second valve to control the cooling oil flow of the rotor based on the flow control amount, and adjusting the opening degree of the first valve when the opening degree of the second valve reaches a threshold value; and the flow control quantity is continuously corrected through closed-loop feedback, so that the real-time temperature of the rotor approaches the preset temperature. According to the invention, the cooling oil quantity can be intelligently distributed in real time, and the performance optimization of the motor under the condition of certain oil quantity is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and particularly to an oil-cooled electric drive cooling oil distribution method, system and vehicle. Background Art

[0002] In the field of new energy vehicles, oil-cooled electric drives have become the mainstream direction of current electric drive design due to their advantages of high efficiency and high speed.

[0003] Currently, the oil quantity distribution of the cooling oil is mainly determined based on the results of working condition tests and motor performance. This distribution form is mainly reflected in the different apertures of the cooling oil channels at the design level, and the flow resistance of the oil channels is used to restrict the flow rate. Its main distribution objects are the reducer and the motor, and this method is simple to operate and easy to implement.

[0004] However, when a permanent magnet synchronous motor is used as the drive motor, the temperature rise characteristics of the motor stator and the motor rotor will change with the working conditions during the distribution of the cooling oil, and the difference between them is large. Specifically, in the low-speed and low-torque driving condition, the permanent magnet motor rotor generates less heat and the temperature rise is not obvious; but when driving at high speed and maintaining the same low torque, due to the significant increase in the eddy current loss of the motor rotor, the temperature rise of the motor rotor is relatively large. At the same time, the stator loss of the motor is generally positively correlated with the motor output torque, and the high-speed and high-torque condition is not common in actual applications. Moreover, if the motor rotor is in a high-temperature state for a long time, there is a risk of demagnetization failure, which will seriously affect the performance and reliability of the motor and even the entire electric drive system.

[0005] Therefore, in order to better protect the motor and avoid the demagnetization failure of the motor rotor due to high temperature, there is an urgent need for a method for distributing the oil quantity of the motor stator and rotor, which can adjust the oil quantity in a closed-loop manner according to the working conditions to optimize the temperature rise of the motor stator and rotor. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to intelligently distribute the cooling oil quantity to the motor stator, motor rotor and reducer in real time.

[0007] In the first aspect of the present invention, an oil-cooled electric drive cooling oil distribution method is provided, and the method includes: Distributing three cooling oil channels to the motor stator, motor rotor and reducer through an oil pump, wherein flow-adjustable first valves and second valves are respectively arranged in the cooling oil channels of the motor stator and the motor rotor; According to the actual detected real-time temperatures of the motor stator and the motor rotor, and the obtained comprehensive working condition information of the electric drive system, combining with the temperature estimation algorithm, estimating the real-time temperature of the motor rotor, and calculating the deviation between the estimated temperature of the motor rotor and the preset temperature; Input the deviation and the deviation change rate into a fuzzy PI controller, and output the proportional parameter and the integral parameter to generate a dynamic flow control quantity; Based on the flow control quantity, preferentially adjust the opening degree of the second valve to control the cooling oil flow of the motor rotor, and when the opening degree of the second valve reaches the threshold value, further adjust the opening degree of the first valve; Continuously correct the flow control quantity through closed-loop feedback, so that the real-time temperature of the motor rotor approaches the preset temperature.

[0008] Furthermore, the fuzzy PI controller includes: A fuzzification interface for converting the deviation and the deviation change rate into fuzzy values; A fuzzy inference engine, input the fuzzy values into the fuzzy inference engine, and perform fuzzy inference in combination with the pre-calibrated temperature rise rules in the knowledge base; and A defuzzification interface for converting the inference result of the fuzzy inference engine into the proportional parameter and the integral parameter.

[0009] Furthermore, the knowledge base is obtained by calibration of an experimental prototype, and includes at least one of the relationship between the stator temperature rise and the speed of the motor, the relationship between the rotor temperature rise and the speed of the motor, and the relationship between the oil pump speed and the temperature rise.

[0010] Furthermore, the rules of the fuzzy inference include: When the absolute value of the deviation is greater than the set threshold and the deviation change rate increases positively, increase the adjustment amplitude of the valve opening; When the absolute value of the deviation tends to zero and the deviation change rate is stable, maintain the current valve opening; When the absolute value of the deviation is less than the set threshold and the deviation change rate decreases negatively, decrease the adjustment amplitude of the valve opening.

[0011] Furthermore, the method for closed-loop feedback correction includes: Use a first-order inertia link To correct the time lag between the estimated temperature and the actual detected temperature of the motor rotor, where Is the inertia time constant; Increase the weighting of the integral parameter under high-speed and high-torque working conditions, and increase the weighting of the proportional parameter under low-speed and low-torque working conditions.

[0012] In a second aspect of the present invention, an oil-cooled electric drive cooling oil distribution system is provided, including: A cooling oil channel module, which is respectively connected to the motor stator, the motor rotor and the reducer through an oil pump, and wherein the cooling oil channels of the motor stator and the motor rotor are respectively provided with a first valve and a second valve; A temperature sensor module for detecting the real-time temperatures of the motor stator and the motor rotor; and A microcontroller module configured to execute the method and output opening control signals for the first valve and the second valve.

[0013] Furthermore, the microcontroller module integrates a fuzzy PI control algorithm, which obtains knowledge base data through calibration of an experimental prototype and dynamically optimizes the proportional parameter and the integral parameter.

[0014] In a third aspect of the present invention, a vehicle is provided, which includes a motor stator, a motor rotor, a speed reducer, and the oil-cooled electric drive cooling oil distribution system as described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: According to the temperatures of the motor stator and the motor rotor and the operating conditions of the electric drive, the present invention controls the opening degrees of the first valve and the second valve based on a fuzzy PI controller, and can adjust the cooling oil quantity in a closed-loop manner, achieving the optimal temperature rise of the motor stator and rotor under a certain oil quantity, and finally controlling the motor temperature within the expected range. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic diagram of the installation of the oil-cooled electric drive oil quantity distribution and regulating valve disclosed in the embodiment of the present invention; Figure 2 It is a block diagram of the control principle of the oil-cooled electric drive oil quantity distribution disclosed in the embodiment of the present invention; Figure 3 It is a block diagram of the control logic flow of the oil-cooled electric drive oil quantity distribution and regulating valve disclosed in the embodiment of the present invention; Figure 4 It is a fuzzy PI control block diagram of the oil-cooled electric drive oil quantity distribution disclosed in the embodiment of the present invention; Figure 5 It is a transfer function block diagram of the fuzzy PI control of the oil-cooled electric drive oil quantity distribution disclosed in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] The present invention aims to provide an intelligent distribution method for the cooling oil of an oil-cooled electric drive, so as to achieve the optimal temperature rise of the motor stator and rotor under a certain amount of oil.

[0020] Specifically, the method mainly includes the following steps: Step 1: Distribute three cooling oil channels to the motor stator, motor rotor, and reducer through an oil pump. Please refer to Figure 1 , and flow-adjustable first valves and second valves are respectively arranged in the cooling oil channels of the motor stator and the motor rotor.

[0021] In this embodiment, the first valve and the second valve are equivalent to the valves A and B shown in the attached drawings.

[0022] Step 2: According to the real-time temperatures of the motor stator and the motor rotor actually detected, and the comprehensive operating condition information of the electric drive system obtained, combined with the temperature estimation algorithm, estimate the real-time temperature of the motor rotor, and calculate the deviation between the estimated temperature of the motor rotor and the preset temperature.

[0023] Please refer to Figure 2 , the temperatures of the motor stator and the motor rotor are detected in real time by temperature sensors mounted on the surfaces of the motor stator and the motor rotor. The comprehensive operating condition information of the electric drive system is collected in real time by the vehicle-mounted controller, and among them, the comprehensive operating condition information includes the motor speed, output torque, and cooling oil flow.

[0024] Among them, the temperature estimation algorithm generally regards each component of the motor (such as stator winding, stator core, rotor winding, rotor core, etc.) as a thermal node with lumped parameters, and describes the heat transfer relationship between them through thermal resistance and heat capacity. According to the law of conservation of energy, a heat balance equation is established, and by solving these equations, the temperatures of each thermal node can be obtained.

[0025] Step 3: Input the deviation and the deviation change rate into the fuzzy PI controller, and output the proportional parameter and the integral parameter to generate a dynamic flow control quantity.

[0026] In this embodiment, the fuzzy PI controller includes a fuzzification interface, a fuzzy inference engine, a knowledge base, and a defuzzification interface. Among them, the fuzzification interface is used to convert the deviation and the rate of change of deviation into fuzzy values. The fuzzy inference engine inputs the fuzzy values into the fuzzy inference engine and performs fuzzy inference in combination with the pre-calibrated temperature rise rules in the knowledge base. The defuzzification interface converts the inference result of the fuzzy inference engine into a proportional parameter and an integral parameter.

[0027] In a further solution of this embodiment, the absolute value of the deviation and the rate of change of deviation are converted into fuzzy values in the fuzzy domain through the fuzzification interface; the fuzzy values are input into the fuzzy inference engine, and fuzzy inference is performed in combination with the pre-calibrated temperature rise rules in the knowledge base; the inference result is converted through the defuzzification interface, and the proportional parameter and the integral parameter are output; the flow control quantity is generated from the proportional parameter and the integral parameter.

[0028] Among them, the knowledge base is obtained by calibration of the experimental prototype and includes at least one of the relationship between the temperature rise of the motor stator and the speed, the relationship between the temperature rise of the motor rotor and the speed, and the relationship between the speed of the oil pump and the temperature rise. After the knowledge base obtains the parameters, adjustment rules or preset valve openings, control parameters, etc. are formulated according to the temperature rise situation of the electronic rotor, so as to quickly respond under some working conditions.

[0029] Among them, the rules of fuzzy inference are: When the absolute value of the deviation is greater than the set threshold and the rate of change of deviation increases positively, the adjustment amplitude of the valve opening is increased.

[0030] When the absolute value of the deviation tends to zero and the rate of change of deviation is stable, the current valve opening is maintained.

[0031] When the absolute value of the deviation is less than the set threshold and the rate of change of deviation decreases negatively, the adjustment amplitude of the valve opening is decreased.

[0032] Step 4: Based on the flow control quantity, preferentially adjust the opening of the second valve to control the cooling oil flow of the motor rotor, and when the opening of the second valve reaches the threshold, further adjust the opening of the first valve.

[0033] Please refer to Figure 3 , since the temperature rise rate of the motor rotor is much higher than that of the motor stator during high-speed operation, and if the temperature of the motor rotor exceeds the Curie point of the permanent magnet material, irreversible demagnetization failure will occur, resulting in a permanent decrease in the performance of the motor. Therefore, in this embodiment, the opening of the adjustable second valve is preferentially changed to adjust the cooling oil flow of the motor rotor; when the opening of the second valve reaches the limit value, the opening of the first valve is further adjusted.

[0034] Step 5: Continuously correct the flow control quantity through closed-loop feedback so that the real-time temperature of the motor rotor approaches the preset temperature.

[0035] Please refer to Figure 4 - 5, the method of closed-loop feedback correction includes: on the one hand, using a first-order inertia link to correct the time lag between the estimated temperature and the actual detected temperature of the motor rotor, where is the inertia time constant; on the other hand, increasing the weighting of the integral parameter under high-speed and high-torque conditions to quickly eliminate the steady-state error; increasing the weighting of the proportional parameter under low-speed and low-torque conditions to enhance the response speed.

[0036] Those skilled in the art further explain that if the set real-time temperature of the estimated motor rotor is accurate, the estimated temperature is only delayed significantly in time compared to the detected temperature, so it can be equivalent to a first-order inertia link . Since the temperature rise generated by the motor operation is a first-order inertia link with hysteresis , the lag time and the inertia time constant can be obtained through experiments, and the valve opening and the actuator are simplified to a proportional function . It can be seen that this method can perform closed-loop control on the motor temperature rise disturbance caused by load changes , so the temperature rise effect of the motor stator and rotor is good.

[0037] The present invention also protects an oil-cooled electric drive cooling oil distribution system, including a cooling oil channel module, a temperature sensor module, and a microcontroller module, where: The cooling oil channel module is respectively connected to the motor stator, the motor rotor, and the reducer through an oil pump, and the cooling oil channels of the motor stator and the motor rotor are respectively provided with a first valve and a second valve.

[0038] The temperature sensor module is used to detect the real-time temperatures of the motor stator and the motor rotor.

[0039] The microcontroller module is configured to execute the above method and output the opening control signals of the first valve and the second valve. The microcontroller module is also integrated with a fuzzy PI control algorithm, and the fuzzy PI control algorithm obtains the knowledge base data through calibration of the experimental prototype and dynamically optimizes the proportional parameter and the integral parameter.

[0040] In addition, a vehicle including a motor rotor, a motor stator, a reducer, and the above oil-cooled electric drive cooling oil distribution system also belongs to the protection scope of the present invention.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An oil-cooling electric drive cooling oil distribution method, characterized in that, The method includes: Distributing three cooling oil channels to the motor stator, motor rotor, and reducer through an oil pump. Among them, the cooling oil channels of the motor stator and the motor rotor are respectively provided with a first valve and a second valve with adjustable flow rates; According to the real-time temperatures of the motor stator and the motor rotor actually detected, as well as the comprehensive operating condition information of the electric drive system obtained, combined with a temperature estimation algorithm, estimate the real-time temperature of the motor rotor, and calculate the deviation between the estimated temperature of the motor rotor and the preset temperature; Input the deviation and the deviation change rate into a fuzzy PI controller, and output a proportional parameter and an integral parameter to generate a dynamic flow control quantity; Based on the flow control quantity, preferentially adjust the opening degree of the second valve to control the cooling oil flow of the motor rotor, and when the opening degree of the second valve reaches a threshold value, further adjust the opening degree of the first valve; Continuously correct the flow control quantity through closed-loop feedback, so that the real-time temperature of the motor rotor approaches the preset temperature.

2. The oil-cooling electric drive cooling oil distribution method according to claim 1, wherein The fuzzy PI controller includes: A fuzzy interface for converting the deviation and the deviation change rate into fuzzy values; A fuzzy inference engine that inputs the fuzzy values into the fuzzy inference engine and performs fuzzy inference in combination with the pre-calibrated temperature rise rules in the knowledge base; and A defuzzification interface for converting the inference result of the fuzzy inference engine into the proportional parameter and the integral parameter.

3. The oil cooling electric drive cooling oil distribution method according to claim 2, wherein, The knowledge base is obtained through calibration of an experimental prototype and includes at least one of the relationship between the temperature rise of the motor stator and the rotational speed, the relationship between the temperature rise of the motor rotor and the rotational speed, and the relationship between the rotational speed of the oil pump and the temperature rise.

4. The oil-cooling electric drive cooling oil distribution method according to claim 2, characterized in that The rules of the fuzzy inference include: When the absolute value of the deviation is greater than the set threshold and the deviation change rate increases positively, increase the valve opening adjustment amplitude; When the absolute value of the deviation tends to zero and the deviation change rate is stable, maintain the current valve opening; When the absolute value of the deviation is less than the set threshold and the deviation change rate decreases negatively, decrease the valve opening adjustment amplitude.

5. The oil cooling electric drive cooling oil distribution method according to claim 1, characterized in that, The method for closed-loop feedback correction includes: Using a first-order inertia link correct the time lag between the estimated temperature and the actually detected temperature of the motor rotor, where is the inertia time constant; Increase the weighting of the integral parameter under high-speed and high-torque operating conditions, and increase the weighting of the proportional parameter under low-speed and low-torque operating conditions.

6. An oil-cooled electric drive cooling oil distribution system, characterized in that, Includes: A cooling oil channel module connected to the motor stator, motor rotor, and reducer respectively through an oil pump, where the cooling oil channels of the motor stator and the motor rotor are respectively provided with a first valve and a second valve; A temperature sensor module for detecting the real-time temperatures of the motor stator and the motor rotor; And A microcontroller module configured to execute the method according to any one of claims 1-5 and output opening control signals for the first valve and the second valve.

7. The oil-cooled electric drive cooling oil distribution system according to claim 6, characterized in that The microcontroller module integrates a fuzzy PI control algorithm, and the fuzzy PI control algorithm obtains knowledge base data through calibration of an experimental prototype and dynamically optimizes the proportional parameter and the integral parameter.

8. A vehicle, characterized in that, Includes a motor stator, a motor rotor, a reducer, and an oil-cooled electric drive cooling oil distribution system according to any one of claims 6-7.

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