Power dividing type hybrid power system and energy consumption optimization control method thereof
By setting up brakes on the sun gear and adopting energy consumption optimization control methods, the internal consumption problem of planetary power shunt hybrid light trucks at high vehicle speeds is solved, and the engine fuel efficiency and the vehicle energy consumption optimization are achieved.
Patent Information
- Application Number
- CN202411961579.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-03-18
AI Technical Summary
The existing planetary power shunt hybrid light trucks have internal consumption at high vehicle speeds, resulting in reduced engine fuel efficiency and high energy consumption.
By setting a brake on the sun wheel, the generator avoids internal consumption at negative speeds, and adopts an energy consumption optimization control method to dynamically calculate the critical vehicle speed of the engine direct drive, and switch to the engine direct drive mode when the vehicle speed is reached, and the engine efficiency is further improved through the torque adjustment of the driving motor.
It effectively avoids internal friction of planetary hybrid vehicles at high speeds, improves the fuel economy of the vehicle, and ensures that the engine is always in the area with the highest fuel thermal efficiency.
Smart Images
Figure CN119636387A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of hybrid electric vehicles, and in particular to a power split hybrid system and an energy consumption optimization control method thereof. Background Art
[0002] The power-split hybrid light truck is a light truck that uses special hybrid technology. The core of the system is to divide the engine power into multiple branches, which are transmitted to the wheel end to drive the vehicle. The power-split hybrid system divides the engine power into two branches: mechanical power flow and electric power flow. The mechanical power flow is directly transmitted to the wheel end through the transmission system, while the electric power flow is converted into electrical energy through the generator and then transmitted to the wheel end through the motor to drive the vehicle. By adjusting the power output ratio, it is possible to keep the internal combustion engine running in the best economic zone at all times, thereby improving fuel economy.
[0003] In order to ensure that the engine of existing hybrid light trucks using planetary power split operates in the optimal area, the engine speed increases slowly as the vehicle speed increases. When the vehicle speed increases to a certain level, the generator speed will drop from positive speed to zero and further become negative speed. When the generator speed becomes negative, the generator changes from generating electricity to consuming energy, causing internal friction and reducing the engine fuel efficiency. Summary of the invention
[0004] In order to overcome the deficiencies of the above-mentioned technology, the purpose of the present invention is to provide a power-split hybrid system and an energy consumption optimization control method thereof, so as to solve the problem that the internal friction of the hybrid light truck with planetary power split at high speed leads to reduced engine fuel efficiency and high energy consumption.
[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0006] A power split hybrid system comprises a generator, wherein the generator is connected to a sun wheel of a planetary gearbox via a primary gear reduction, and the special feature of the system is that a brake is arranged on the sun wheel.
[0007] Furthermore, the power-split hybrid system is used for a hybrid light truck.
[0008] The energy consumption optimization control method of the power split hybrid system is special in that it includes the following steps:
[0009] 1) Determine the optimal operating curve and operating range of the engine; based on the optimal operating curve and operating range of the engine, determine the engine operating speed range of the vehicle at high speed under the current vehicle load, and calculate the vehicle speed when the generator speed is zero;
[0010] 2) Calculate the engine power lost by the generator due to the internal friction of the vehicle at different negative speeds when the vehicle speed exceeds the speed at which the generator speed is zero;
[0011] 3) Calculate the engine fuel consumption rate of the current vehicle after direct drive at different vehicle speeds when the vehicle speed exceeds the speed at which the generator speed is zero;
[0012] 4) Based on the engine fuel consumption rate after direct drive, calculate the engine power loss of the current vehicle after direct drive at different vehicle speeds;
[0013] 5) When the engine power loss after direct drive is the same as the engine power loss of the generator due to the internal friction of the whole vehicle at different negative speeds, the current vehicle speed is obtained as the critical vehicle speed;
[0014] 6) If the current vehicle speed reaches the critical speed, the generator is controlled to stop outputting torque, and the vehicle switches to engine direct drive mode. At this time, the engine torque is adjusted by the drive motor. If the drive motor torque is positive, the drive motor assists the drive. If the drive motor torque is negative, the drive motor generates electricity to increase the engine load.
[0015] As a preferred solution, in step 1), the engine optimal operating curve and operating range are determined by the engine map; the high vehicle speed refers to a vehicle speed of not less than 65 km / h. The engine map is a map of engine torque, speed and fuel consumption rate, and the current fuel consumption rate of the engine can be obtained through the current engine speed and torque.
[0016] Furthermore, in step 2), the calculation formula of the engine power lost by the generator due to the internal friction of the whole vehicle at different negative speeds is as follows:
[0017]
[0018] Where: P mg1loss is the engine power lost due to vehicle internal friction at different negative speeds; T e,req is the engine required torque; f k1 is the planetary gear characteristic coefficient; ω mg1,req The required speed of the generator.
[0019] As a preferred solution, in step 3), the engine fuel consumption rate is based on the engine required torque and speed after direct drive, and is obtained through the engine map;
[0020] The engine required torque and speed after direct drive are obtained by the following formula:
[0021]
[0022] T e,req =Twhl,req / i fd ;
[0023] Where: e,req T is the engine required speed; whl,req is the wheel torque requirement, obtained through the vehicle throttle map; T e,req is the engine required torque; whl,req is the required wheel speed; i fd The vehicle throttle map is a map of the vehicle's current speed, throttle depth and required torque. The vehicle's current required torque is obtained through the current speed and throttle depth.
[0024] As a preferred solution, in step 4), the calculation formula for the engine power loss after direct drive is as follows:
[0025]
[0026] Where P engloss P is the engine power loss after direct drive; e,req Be is the engine power required after direct drive; dv is the engine fuel consumption rate under direct drive condition; Be hev It is the engine fuel consumption rate of the vehicle in hybrid state at the current speed.
[0027] Is the percentage of power lost due to the degradation of engine fuel consumption. hev Available through the engine map.
[0028] As a preferred solution, in step 6), the process of controlling the generator to stop outputting torque is achieved by a brake, and the brake is arranged on a sun gear connected to the generator.
[0029] As a preferred solution, in step 6), the driving motor torque is calculated as follows:
[0030]
[0031] Where, T mg2,req Adjust the torque for the drive motor; T whl,req is the wheel torque requirement; fd Mainly reduce efficiency; T e,target is the optimal torque at the current engine speed; i amt is the transmission ratio of the drive motor.
[0032] Wheel torque required T whl,req It can be obtained from the vehicle throttle map. The engine torque is adjusted by the drive motor to achieve decoupling from the vehicle's required torque, and further adjust the engine torque to a lower fuel consumption area.
[0033] A vehicle controller is special in that it includes an energy consumption optimization control unit for executing the above energy consumption optimization control method.
[0034] Compared with the prior art, the present invention has the following beneficial effects:
[0035] The present invention provides a power split hybrid system and an energy consumption optimization control method thereof, which avoids the internal friction of the planetary hybrid vehicle at high speeds by adding a brake to the sun gear, and avoids the situation where the engine efficiency loss after direct drive is greater than the internal friction when the vehicle is light through the energy consumption optimization control method. The required direct drive speed of the vehicle is dynamically calculated by the power loss under direct drive of the engine, thereby improving the fuel economy of the vehicle. When the engine is directly driven, the engine efficiency is further improved by adjusting the torque of the drive motor. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 It is a schematic diagram of the architecture of a power split hybrid system in the prior art;
[0037] Figure 2 It is a schematic diagram of the architecture of a power split hybrid system in a specific embodiment of the present invention;
[0038] Figure 3 is a lever diagram;
[0039] In the figure: 1. Engine; 2. Shock absorber; 3. Brake; 4. Sun gear; 5. Generator; 6. Two-speed hybrid transmission; 7. Ring gear; 8. Drive motor; 9. Planetary carrier; 10. Wheel. DETAILED DESCRIPTION
[0040] In order to better explain the present invention, the main contents of the present invention are further explained below in conjunction with the drawings and specific embodiments, but the contents of the present invention are not limited to the following embodiments.
[0041] Example 1
[0042] like Figure 1 The figure shows a power split hybrid system, including an engine 1, which is connected to a planetary carrier 9 through a shock absorber 2. The planetary carrier 9, the sun gear 4, the planetary gears and the ring gear 7 form a planetary gearbox, which is used to reduce the transmission ratio and increase the torque of the motor. The planetary gearbox can decouple the speed and torque of the engine 1 from the wheel end, ensure that the engine 1 works on the optimal fuel consumption line, and improve the thermal efficiency of the engine fuel. The generator 5 is connected to the sun gear 4 through a first-stage gear reduction, and the drive motor 8 is connected to the ring gear 7 through a two-speed hybrid gearbox 6, and the ring gear 7 is connected to the wheel 10. The structure of the above power split hybrid system is a prior art and will not be elaborated here.
[0043] like Figure 2 As shown, the present invention is provided with a brake 3 on the sun gear 4. When the rotation speed of the generator 5 drops to a certain value, the brake 3 is locked and the generator 5 stops outputting torque.
[0044] To ensure that the engine 1 works in the optimal area, the speed of the engine 1 increases slowly as the vehicle speed increases. When the vehicle speed increases to a certain speed, the speed of the generator 5 will start to decrease from a positive speed. When the vehicle speed increases to a certain speed, the speed of the generator 5 will drop to zero. As the vehicle speed continues to increase, the speed of the generator 5 will further become a negative speed. Figure 3 As shown. When the generator 5 changes to a negative speed, the generator 5 changes from generating electricity to consuming energy, which forms internal friction and reduces the fuel efficiency of the engine 1. Therefore, the present invention adds a brake 3 to the sun gear 4. When the vehicle speed approaches the critical speed, the brake 3 can be locked, the sun gear 4 speed is 0, and the generator 5 has no torque output. All the torque of the engine 1 is output from the ring gear 7, and the whole vehicle realizes direct drive of the engine 1 to avoid internal friction.
[0045] Example 2
[0046] For a hybrid light truck using the power split hybrid system in Example 1, when its brake is locked, the sun gear speed is 0, and the generator has no torque output. All the engine torque is output from the ring gear, and the whole vehicle realizes direct engine drive, which can effectively avoid internal friction. At this time, the engine speed and torque calculation formula are as follows:
[0047]
[0048] T e,req =T whl,req / i fd ;
[0049] Where: e,req T is the engine required speed; whl,req is the wheel torque requirement, obtained through the vehicle throttle map; T e,req is the engine required torque; whl,req is the required wheel speed; i fd Main reducer speed ratio.
[0050] The above-mentioned power split hybrid system can effectively avoid internal friction, but if the brake is locked when the generator just changes to negative speed, the following situation may occur: when the high-speed torque required by the whole vehicle is small, the engine is in a high-speed and low-torque state, and the engine fuel consumption rate may deteriorate by more than 20% compared with the optimal area, and the energy loss is greater than the internal friction loss. At this time, the fuel consumption control strategy needs to be further optimized. Therefore, this embodiment provides an energy consumption optimization control method for a power split hybrid system, which specifically includes the following steps:
[0051] 1) Determine the optimal working curve and working range of the engine through the engine map, determine the engine working speed range of the current vehicle at high speed, and calculate the speed at which the generator speed is 0 based on the determined engine working speed range. High speed means that the speed is not less than 65km / h.
[0052] 2) Calculate the engine power lost by the current vehicle generator at different negative speeds due to the internal friction of the vehicle when the vehicle speed exceeds the speed at which the generator speed is zero:
[0053]
[0054] Where: P mg1loss is the engine power lost due to vehicle internal friction at different negative speeds of the generator; T e,req is the engine required torque; f k1 is the planetary gear characteristic coefficient; ω mg1,req The required speed of the generator.
[0055] Among them, the engine demand torque T e,req Through the engine demand power and engine demand speed ω e,req Obtained, with wheel power requirement p whl,req As the engine required power. The calculation formula is as follows:
[0056] T e,req =p whl,req ×9549 / ω e,req .
[0057] In the above formula, the engine required speed ω e,req Through the engine optimal line MAP (engine required speed and engine required power relationship) and the wheel required power p whl,req Solve, the calculation formula is as follows:
[0058] ω e,req =ω(p whl,req ).
[0059] Generator required speed ω mg1,req By driving the motor required speed ω mg2,req and engine speed requirement ω e,req The calculation formula is as follows:
[0060] ω mg1,req =(1+f k1 )×ω e,req -f k1 ×ω mg2,req ;
[0061] in:
[0062]
[0063] 3) After the vehicle reaches a speed where the generator speed is 0, the current required torque of the vehicle is calculated through the vehicle throttle map. The current required torque of the vehicle is the wheel required torque T whl,req Before the brake is locked, the VCU calculates the engine torque and speed required by the vehicle in direct drive according to the following formula, and confirms the engine fuel consumption rate Be after direct drive through the engine map. dv .
[0064] The calculation formula for the engine required torque and speed after direct drive is as follows:
[0065]
[0066] T e,req =T whl,req / i fd ;
[0067] Where: e,req T is the engine required speed; whl,req is the wheel torque required; T e,req is the engine required torque; whl,req is the required wheel speed; i fd Main reduction ratio.
[0068] 4) Calculate the engine power loss after direct drive:
[0069]
[0070] Where P engloss P is the engine power loss after direct drive; e req Be is the engine power required after direct drive; dv is the engine fuel consumption rate under direct drive condition; Be hev It is the engine fuel consumption rate of the current vehicle in hybrid state at the current speed, which can be obtained through the engine map. is the percentage of power lost due to degradation of the engine's fuel consumption.
[0071] 5) Compare P mg1loss and P engloss , when P engloss =P mg1loss When the vehicle speed is calculated by the current engine power loss, the critical speed at which the direct drive efficiency is better than the hybrid can be calculated. The required torque of the vehicle is different under different vehicle weight conditions, so the calculated critical speed is different. In this way, the optimal critical direct drive speed of the vehicle can be determined according to different vehicle weights.
[0072] 6) When the vehicle speed reaches the critical speed, the brake is locked, the generator stops outputting torque, and then the engine is connected in parallel with the drive motor. At this time, the engine torque can be adjusted by the drive motor to achieve decoupling from the vehicle's required torque, and further adjust the engine torque to a lower fuel consumption area. At this time, the drive motor adjustment torque is calculated as follows:
[0073]
[0074] Where, T AMT,req Adjust the torque for the drive motor; T whl,req is the wheel torque requirement, obtained from the vehicle throttle map; i fd With η fd is the main reduction ratio and main reduction efficiency; T e,target is the optimal torque at the current engine speed; i amt is the transmission ratio of the drive motor. If the torque of the drive motor is positive, the drive motor assists the drive, and if the torque is negative, the drive motor generates electricity to increase the engine load.
[0075] The energy consumption optimization control method of the present invention is further described below by taking a power-split hybrid light truck as an example in which the energy consumption optimization control method of the present invention is applied.
[0076] The current vehicle is a hybrid light truck with a total weight of 4.5 tons.
[0077] The method of the present invention is used to optimize the energy consumption of the hybrid light truck, including the following steps:
[0078] First, calculate the vehicle speed when the generator speed is zero, which is 65km / h.
[0079] Subsequently, the engine power lost by the generator due to the internal friction of the vehicle at different negative speeds and the engine power loss of the current vehicle after direct drive at different speeds are calculated when the vehicle speed exceeds 65km / h, and the critical vehicle speed is determined to be 80km / h when the engine power loss after direct drive is the same as the engine power lost by the generator due to the internal friction of the vehicle at different negative speeds.
[0080] The critical speed obtained with the current vehicle load is 80km / h. When the current vehicle speed reaches 80km / h, the brake is locked, the generator stops outputting torque, and the vehicle switches to engine direct drive mode. When the speed is lower than 80km / h, the brake is opened, the generator outputs torque, and the vehicle remains in hybrid mode.
[0081] With the current vehicle load and the brakes locked at the critical speed, the vehicle's fuel consumption per 100 kilometers under the CHTC-LT condition is 7.9L / 100km.
[0082] With the current vehicle load, when the brakes are not used, the fuel consumption of the vehicle under CHTC-LT conditions is 8.1L / 100km.
[0083] With the current vehicle load, when the brake is locked when the generator speed is zero, that is, the vehicle speed is 65km / h, the fuel consumption of the whole vehicle is 8.2L / 100km under the CHTC-LT condition.
[0084] Example 3
[0085] A vehicle controller comprises an energy consumption optimization control unit for executing the above energy consumption optimization control method.
[0086] The above energy consumption optimization control method performs a calculation in a trip through the energy consumption optimization control unit, obtains the relevant parameters of the current vehicle through the vehicle controller, and calculates the critical vehicle speed at which the direct drive efficiency corresponding to the current vehicle load is better than the hybrid based on the relevant parameters of the current vehicle. When the vehicle speed reaches the critical speed, the lock is controlled to lock, the generator stops outputting torque, and the engine is directly driven. When the vehicle speed drops below the critical speed, the lock is opened, the generator outputs torque, and hybrid drive is performed.
[0087] The present invention firstly avoids the internal friction of the planetary hybrid vehicle at high speed by adding a brake to the sun gear, and dynamically calculates the required direct-drive speed of the vehicle through the power loss under direct-drive of the engine. After the engine is directly driven, the torque of the driving motor is adjusted to further improve the engine efficiency, ensuring that the vehicle engine is always in the area with the highest fuel thermal efficiency at different weights.
[0088] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection claimed in the present invention is defined by the attached claims and their equivalents. Other parts not described belong to the prior art.
Claims
1. A power split hybrid system, comprising a generator, wherein the generator is connected to the sun gear of a planetary gearbox through a primary gear reduction, and is characterized in that: The sun gear is provided with a brake.
2. The power split hybrid system according to claim 1, characterized in that: The power split hybrid system is used for a hybrid light truck.
3. A method for optimizing energy consumption control of a power split hybrid system, characterized in that: The following steps are involved: 1) Determine the optimal operating curve and operating range of the engine; based on the optimal operating curve and operating range of the engine, determine the engine operating speed range of the vehicle at high speed under the current vehicle load, and calculate the vehicle speed when the generator speed is zero; 2) Calculate the engine power lost by the generator due to the internal friction of the vehicle at different negative speeds when the vehicle speed exceeds the speed at which the generator speed is zero; 3) Calculate the engine fuel consumption rate of the current vehicle after direct drive at different vehicle speeds when the vehicle speed exceeds the speed at which the generator speed is zero; 4) Based on the engine fuel consumption rate after direct drive, calculate the engine power loss of the current vehicle after direct drive at different vehicle speeds; 5) When the engine power loss after direct drive is the same as the engine power loss of the generator due to the internal friction of the whole vehicle at different negative speeds, the current vehicle speed is obtained as the critical vehicle speed; 6) If the current vehicle speed reaches the critical speed, the generator is controlled to stop outputting torque, and the vehicle switches to engine direct drive mode. At this time, the engine torque is adjusted by the drive motor. If the drive motor torque is positive, the drive motor assists the drive. If the drive motor torque is negative, the drive motor generates electricity to increase the engine load.
4. The energy consumption optimization control method according to claim 3 is characterized in that: In step 1), the optimal operating curve and operating range of the engine are determined by the engine map; the high vehicle speed refers to a vehicle speed not less than 65 km / h.
5. The energy consumption optimization control method according to claim 3, characterized in that: In step 2), the calculation formula of the engine power lost by the generator due to the internal friction of the whole vehicle at different negative speeds is as follows: Where: P mg1loss is the engine power lost due to vehicle internal friction at different negative speeds; T e,req is the engine required torque; f k1 is the planetary gear characteristic coefficient; ω mg1,req The required speed of the generator.
6. The energy consumption optimization control method according to claim 3, characterized in that: In step 3), the engine fuel consumption rate is based on the engine required torque and speed after direct drive, and is obtained through the engine map; The engine required torque and speed after direct drive are obtained by the following formula: T e,req =T whl,req / i fd ; Where: e,req is the engine required speed; T whl,req is the wheel torque requirement, obtained through the vehicle throttle map; T e,req is the engine required torque; whl,req is the required wheel speed; i fd Main reducer speed ratio.
7. The energy consumption optimization control method according to claim 3 is characterized in that: In step 4), the calculation formula of the engine power loss after direct drive is as follows: Where P engloss P is the engine power loss after direct drive; e,req Be is the engine power required after direct drive; dv is the engine fuel consumption rate under direct drive condition; Be hev It is the engine fuel consumption rate of the vehicle in hybrid state at the current speed.
8. The energy consumption optimization control method according to claim 3, characterized in that: In step 6), the process of controlling the generator to stop outputting torque is achieved by a brake, and the brake is arranged on a sun gear connected to the generator.
9. The energy consumption optimization control method according to any one of claims 3 to 8, characterized in that: In step 6), the driving motor torque is calculated as follows: Where, T mg2,req Adjust the torque for the drive motor; T whl,req is the wheel torque requirement; η fd Mainly reduce efficiency; T e,target is the optimal torque at the current engine speed; i amt is the transmission ratio of the drive motor.
10. A vehicle controller, characterized in that: It comprises an energy consumption optimization control unit, which is used to execute the energy consumption optimization control method described in any one of claims 3 to 9.