Power split hybrid power device and control method thereof

Abstract

According to the power split hybrid power device and the control method thereof, through cooperative control of a planetary gear structure and a motor, a power split system with an engine running at the highest efficiency point all the time is achieved, and the power split hybrid power device has the advantages of being efficient and intelligent. A power split hybrid power device comprises an engine, a first planetary gear device, a first motor, a second planetary gear device, a second motor, a first-stage speed reducer, a second-stage speed reducer and a control system. The first planetary gear device is connected with an engine to serve as a power input end, is connected with the second planetary gear device in parallel through the first-stage speed reducer and then is connected to a driving shaft of a vehicle through the second-stage speed reducer and the differential mechanism, and is responsible for providing parallel driving force or kinetic energy recovery for the vehicle. The control system comprises a motor control unit, a battery management unit, an inverter control unit, an analog quantity conditioning unit, a digital switching value conditioning unit and the like; according to the vehicle driving working condition, the driving mode is intelligently switched, and power output of the engine and the motor is adjusted.

Description

Technical Field

[0001] The present invention belongs to the technical field of engine application, and in particular relates to a power split hybrid power device and a control method thereof. Background Art

[0002] In recent years, hybrid power technology has become an important solution for automobile energy conservation and emission reduction, which is mainly divided into three forms: series, parallel and hybrid.

[0003] In a series hybrid system, the fuel engine is only responsible for driving the generator to generate electricity, and the electric motor alone drives the vehicle. This method can ensure that the engine operates in a relatively high efficiency range to a certain extent, but since the power requires multiple energy conversions (the engine drives the generator to generate electricity, and then the motor drives the vehicle), the energy loss is relatively large. The parallel hybrid system provides driving force through the engine and the motor, and dynamically distributes the power source according to driving needs; in this way, the engine can directly drive the vehicle under high-speed conditions, but because the motor and the engine work together, the engine usually cannot maintain the highest efficiency point. The hybrid system combines the characteristics of series and parallel, and realizes the diversion and confluence of power through a complex transmission mechanism, so that the engine can approach the high-efficiency zone in a wider range; however, this system has a complex structure, large mechanical losses, and high manufacturing and maintenance costs.

[0004] In summary, the main defects and causes of existing hybrid power systems include:

[0005] 1) Insufficient engine operating efficiency: Most existing solutions can only ensure that the engine operates in the high-efficiency zone, but cannot accurately control the engine to always maintain the highest efficiency point.

[0006] 2) Large energy conversion loss: The series scheme has multiple energy conversion problems, resulting in a decrease in overall energy utilization.

[0007] 3) High mechanical structure complexity: Most of them rely on complex planetary gear structure and multi-clutch design, which increases manufacturing cost and maintenance difficulty.

[0008] 4) Driving mode response is not flexible enough: The existing system has a lag in switching between different driving modes and fails to adjust power distribution according to working conditions in real time, affecting driving experience and system efficiency. Summary of the invention

[0009] In order to make up for the deficiencies of the prior art, the present invention aims to provide a power-split hybrid power device and a control method thereof, which realizes a power-split system in which the engine always runs at the highest efficiency point through coordinated control of a planetary gear structure and a motor, and has the characteristics of high efficiency, simplification and intelligence.

[0010] The technical problem solved by the present invention can be achieved through the following technical solutions:

[0011] In one aspect, a power split hybrid device is provided, comprising:

[0012] An engine, installed in a powertrain of the vehicle and connected to the first planetary gear device via an output shaft, for providing a main power of the vehicle;

[0013] A first planetary gear device, used to split power into driving and generating power, wherein the planet carrier is connected to the engine as the input end of the power, the ring gear is connected to the wheel drive shaft through the primary reducer, the secondary reducer and the differential as the output end, and the center gear is connected to the first motor for generating power and controlling the engine speed;

[0014] A first motor is installed beside the engine, controls the engine speed through a first planetary gear device and generates electricity, and its output is connected to an inverter to store the generated energy in a battery, and can also generate electricity in a parking condition;

[0015] The second planetary gear device has a fixed planet carrier and a ring gear connected to the wheel drive shaft through a primary reducer, a secondary reducer and a differential, and is responsible for providing auxiliary driving force or kinetic energy recovery for the vehicle;

[0016] A second motor is connected to the central wheel of the second planetary gear device, and dynamically adjusts the torque output according to the accelerator pedal and vehicle speed signal for auxiliary driving or braking kinetic energy recovery;

[0017] A primary reducer synchronously connecting the ring gears of the first planetary gear device and the second planetary gear device;

[0018] The secondary reducer and differential are the transmission mechanisms used to drive the vehicle.

[0019] Furthermore, it also includes a control system for intelligently switching driving modes according to the vehicle's driving conditions, controlling the power generation frequency and voltage of the first motor in real time, and adjusting the engine speed and power output of the second motor; the control system includes a motor control unit, a battery management unit, an inverter control unit, an analog quantity conditioning unit, and a digital switch quantity conditioning unit.

[0020] On the other hand, a control method based on the above-mentioned power split hybrid device is provided, comprising the following contents:

[0021] When the battery power is higher than the set minimum value, the second motor provides pure electric driving force, the engine does not start, and the second motor controls the vehicle driving according to the accelerator pedal opening signal and the vehicle speed signal;

[0022] When the battery power is lower than the set minimum value, the engine starts, and the main driving force is output through the planetary carrier of the first planetary gear device. The first motor adjusts the engine speed by controlling the power generation frequency and voltage to keep it running at the highest efficiency point. The second motor controls power generation or driving according to the accelerator pedal opening signal and vehicle speed signal. It will not switch to pure electric operation mode until the battery power exceeds the set hybrid maximum power.

[0023] When you release the accelerator or brake, the second motor enters the power generation mode, converting the vehicle's kinetic energy into electrical energy through the second planetary gear device and storing it in the battery;

[0024] When the battery power continues to drop to 5% below the set minimum power, the first motor increases the engine speed by controlling the power generation frequency and voltage to maintain its output of greater power. The second motor controls power generation or driving according to the accelerator pedal opening signal and the vehicle speed signal, but its maximum power is subject to the power generated by the first generator to ensure that the battery power no longer continues to drop.

[0025] Furthermore, when the vehicle battery charge reaches a set high value (set by the driver, generally the minimum value plus 5%-20%), the control system shuts down the engine and switches to pure electric drive mode at all speeds.

[0026] Furthermore, if the battery power is low to a set minimum value, the control system starts the engine, and the power is diverted to the ring gear of the first planetary gear device to drive the vehicle, while driving the first motor through its center wheel to generate electricity. The speed of the first motor controls the engine speed at the optimal efficiency point, and the second motor determines whether to generate electricity or drive according to the accelerator pedal opening signal and the vehicle speed signal.

[0027] Furthermore, the control strategy of the first motor is as follows: the first motor controls the speed of the engine by adjusting the power generation frequency and voltage according to the vehicle speed to ensure that it always runs at the highest efficiency speed point; when the battery power continues to decrease, the engine speed is increased to increase the power output of the engine; the engine controls the fuel injection amount according to the output torque of the best efficiency point at the operating speed, controls the power output, and meets the requirements of optimal efficiency.

[0028] Furthermore, the engine outputs power through the planetary carrier of the first planetary gear device, and drives the vehicle and the first motor to generate electricity at the same time. The first motor controls the engine speed by adjusting the power generation frequency and voltage to ensure that it always runs at the highest efficiency point. The specific power distribution relationship formula is as follows:

[0029] The speed of the first motor n 1 With the engine speed n f , the rotational speed n of the ring gear of the first planetary gear device in relation to the vehicle speed q , the reduction ratio i of the first planetary gear device 1The relationship is:

[0030] n 1 =n f +i 1 ·(n f -n q ),

[0031] The ring gear output torque M of the first planetary gear device q With engine torque M f The relationship is:

[0032]

[0033] The torque M of the first motor 1 With engine torque M f The relationship is:

[0034]

[0035] Furthermore, the control system optimizes the output torque or energy recovery intensity of the second motor according to the throttle opening signal and the energy recovery coefficient according to different driving modes, and the second motor dynamically adjusts the output mode according to the real-time working conditions, including:

[0036] Driving mode: Provides auxiliary driving force and cooperates with the engine to drive the vehicle;

[0037] Power generation mode: Recover kinetic energy during braking and convert it into electrical energy and store it in the battery.

[0038] Furthermore, the control system intelligently switches between pure electric mode and hybrid power mode according to the battery power:

[0039] When the battery power is higher than the set value, the pure electric mode is prioritized and the second motor drives the vehicle independently;

[0040] When the battery power is lower than the set value, it switches to hybrid mode, and the engine and the second motor work together;

[0041] When the battery charge is below 5% of the set minimum charge, the control system increases the engine speed, thereby increasing the engine output power, while limiting the output power of the second motor to keep the battery charge from continuing to decline, thereby avoiding a "stall" situation.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] (1) Improved fuel economy: The engine of the present invention always operates at the highest efficiency point, and it is estimated that the fuel efficiency is significantly improved by more than 10%.

[0044] (2) Simplified mechanical structure: The present invention eliminates multiple clutches and multiple brakes in the traditional hybrid system and adopts a planetary gear device to achieve power distribution and energy recovery, thereby reducing system complexity and manufacturing costs.

[0045] (3) Intelligent driving mode: The present invention realizes seamless switching between pure electric and hybrid modes, meeting various operating conditions such as low-speed driving in cities and high-speed cruising.

[0046] (4) Enhanced adaptability: The present invention can dynamically adjust the coordinated operation of the engine and the motor to ensure power continuity and driving stability under extreme driving conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a structural diagram of a hybrid power device of the present invention;

[0048] Figure 2 It is a cross-sectional view of the hybrid power device of the present invention.

[0049] In the figure: 100 - engine, 200 - first planetary gear device, 300 - first motor, 400 - second planetary gear device, 500 - second motor, 600 - primary reducer, 700 - secondary reducer, 800 - differential. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] like Figure 1 and Figure 2As shown, a power split hybrid device includes an engine 100, a first planetary gear device 200, a first motor 300, a second planetary gear device 400, a second motor 500, a primary reducer 600, a secondary reducer 700, a differential 800 and a control system, wherein the engine 100 is installed in the powertrain of the vehicle and is connected to the first planetary gear device 200 through an output shaft to provide the main power of the vehicle; the first planetary gear device 200 splits the power into driving and generating electricity, its planet carrier is connected to the engine 100 as the input end of the power, and its ring gear is connected to the wheel drive shaft as the output end through the primary reducer 600, the secondary reducer 700 and the differential 800, and its center wheel is connected to the first planetary gear device 200. The first motor 300 is connected to the first planetary gear device 200 for power generation and engine speed control; the first motor 300 is installed next to the engine 100, controls the speed of the engine 100 and generates electricity through the first planetary gear device 200, and its output is connected to the inverter to store the generated energy in the battery, and can also generate electricity under parking conditions; the planet carrier of the second planetary gear device 400 is fixed, and its ring gear is connected to the wheel drive shaft through the primary reducer 600, the secondary reducer 700 and the differential 800, which is responsible for providing auxiliary driving force or kinetic energy recovery for the vehicle; the second motor 500 is connected to the central wheel of the second planetary gear device 400, and dynamically adjusts the torque output according to the accelerator pedal and vehicle speed signal for auxiliary driving or braking kinetic energy recovery.

[0052] The primary reducer 600 is synchronously connected to the ring gears of the first planetary gear device 200 and the second planetary gear device 400; the secondary reducer 700 and the differential 800 are used to drive the transmission mechanism of the vehicle. The first planetary gear device 200 is connected to the engine 100 as the input end of the power, and is connected to the driving shaft of the vehicle through the secondary reducer 700 and the differential 800 after being connected in parallel with the second planetary gear device 400 through the primary reducer 600, and is responsible for providing parallel driving force or kinetic energy recovery for the vehicle.

[0053] The control system includes a motor control unit, a battery management unit, an inverter control unit, an analog quantity conditioning unit, a digital switch quantity conditioning unit, etc., which are used to intelligently switch the driving mode according to the vehicle's driving conditions, control the power generation frequency and voltage of the first motor 300 in real time, and adjust the engine speed and the power output of the second motor 500.

[0054] It can be understood that the power of the engine 100 is split through the first planetary gear device 200, part of which drives the vehicle through the ring gear, and part of which drives the first motor 300 to generate electricity through the central wheel. The present application eliminates multiple clutches and brakes in the traditional hybrid system, and adopts a planetary gear device to achieve power splitting and merging. Through the first planetary gear device 200 and the second planetary gear device 400 combined with the precise control of the first motor 300, the speed of the engine 100 is strictly maintained at its highest efficiency point, significantly improving fuel efficiency. The parallel power design is adopted to meet the power requirements of the vehicle while using the excess engine power for power generation and storage, avoiding the multi-stage energy conversion loss of the traditional series system.

[0055] The control method based on the above power split hybrid power device includes the following contents:

[0056] (1) When the battery power level is higher than a set minimum value (set by the driver, the setting range is initially set to 30%-70%), the second motor 500 provides pure electric driving force, the engine 100 does not start working, and the second motor 500 controls the vehicle driving according to the accelerator pedal opening signal and the vehicle speed signal.

[0057] (2) When the battery power is lower than the set minimum value, the engine 100 starts and outputs the main driving force through the planetary carrier of the first planetary gear device 200. The first motor 300 adjusts the speed of the engine 100 by controlling the power generation frequency and voltage to keep it running at the highest efficiency point. The second motor 500 controls power generation or driving according to the accelerator pedal opening signal and the vehicle speed signal until the battery power is higher than the set hybrid maximum power and then switches to the pure electric operation mode; the power is diverted to the ring gear of the first planetary gear device 200 to drive the vehicle, and at the same time, the center wheel drives the first motor 300 to generate electricity. The speed of the engine 100 is controlled by the speed of the first motor 300 to be at the best efficiency point. The second motor 500 determines whether to generate electricity or drive according to the accelerator pedal opening signal and the vehicle speed signal.

[0058] (3) When the accelerator or brake is released, the second motor 500 enters the power generation mode, converting the vehicle's kinetic energy into electrical energy through the second planetary gear device 400 and storing it in the battery.

[0059] (4) When the battery power continues to drop to 5% below the set minimum power, the first motor 300 increases the speed of the engine 100 by controlling the power generation frequency and voltage to maintain its greater power output. The second motor 500 controls power generation or driving according to the accelerator pedal opening signal and the vehicle speed signal, but its maximum power is subject to the power generated by the first generator 200 to ensure that the battery power does not continue to drop, avoid the "stall" problem caused by power interruption or low power, and ensure driving safety.

[0060] (5) When the vehicle battery charge reaches a set high value, the control system shuts down the engine 100 and switches to pure electric drive mode at all speeds.

[0061] The control strategy of the first motor 300 of the present application is: the first motor 300 controls the speed of the engine 100 by adjusting the power generation frequency and voltage according to the vehicle speed, ensuring that it always runs at the highest efficiency speed point; when the battery power continues to decrease, the power output of the engine 100 is increased by increasing the speed of the engine 100; the engine 100 controls the injection amount according to the output torque of the best efficiency point at the operating speed, controls the power output, and meets the requirements of optimal efficiency.

[0062] The engine 100 outputs power through the planet carrier of the first planetary gear device 200, and drives the vehicle and the first motor 300 to generate electricity. The first motor 300 controls the speed of the engine 100 by adjusting the power generation frequency and voltage to ensure that it always runs at the highest efficiency point. The specific power distribution relationship formula is as follows:

[0063] The rotation speed n of the first electric machine 300 1 The speed n of the engine 100 f , the rotation speed n of the ring gear of the first planetary gear device 200 related to the vehicle speed q , the reduction ratio i of the first planetary gear device 200 1 The relationship is:

[0064] n 1 =n f +i 1 ·(n f -n q ),

[0065] The ring gear output torque M of the first planetary gear device 200 q With engine 100M torque f The relationship is:

[0066]

[0067] The torque M of the first electric machine 300 1 With engine 100M torque f The relationship is:

[0068]

[0069] The control system of the present application optimizes the output torque or energy recovery intensity of the second motor 500 according to the different driving modes (economy / sports), the throttle opening signal and the energy recovery coefficient, and the second motor 500 dynamically adjusts the output mode according to the real-time working conditions, including:

[0070] 1) Driving mode: providing parallel driving force and driving the vehicle in coordination with the engine 100;

[0071] 2) Power generation mode: Recover kinetic energy during braking and convert it into electrical energy and store it in the battery.

[0072] Through the precise control of the second motor 500, efficient braking kinetic energy recovery is achieved, and energy distribution is dynamically adjusted according to actual working conditions to improve overall energy utilization.

[0073] The control system can maintain high system efficiency under both low-speed and high-speed conditions, and intelligently switch between pure electric mode and hybrid power mode according to the battery power and vehicle operating conditions: when the battery power is higher than the set value, the pure electric mode is prioritized, and the second motor 500 independently drives the vehicle; when the battery power is lower than the set value, it switches to hybrid mode, and the engine 100 and the second motor 500 work together; when the battery power is less than 5% of the set minimum power, the control system increases the engine output power by increasing the engine 100 speed, and at the same time limits the output power of the second motor 500 to prevent the battery power from continuing to decline.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power split hybrid device, characterized in that: include An engine (100) is installed in a powertrain of a vehicle and connected to a first planetary gear device (200) via an output shaft to provide main power for the vehicle; A first planetary gear device (200) is used to split power into driving and power generation, wherein the planet carrier is connected to the engine (100) as a power input end, and the ring gear is connected to the wheel drive shaft via a primary reducer (600), a secondary reducer (700) and a differential (800) as an output end, and the center wheel is connected to the first motor (300) for power generation and engine speed control; A first motor (300) is installed next to the engine (100), controls the speed of the engine (100) through the first planetary gear device (200) and generates electricity, and its output is connected to an inverter to store the generated energy in a battery, and can also generate electricity in a parking condition; The second planetary gear device (400) has a fixed planet carrier and a ring gear connected to a wheel drive shaft via a primary reducer (600), a secondary reducer (700) and a differential (800), and is responsible for providing auxiliary driving force or kinetic energy recovery for the vehicle; A second motor (500) is connected to the central wheel of the second planetary gear device (400), and dynamically adjusts the torque output according to the accelerator pedal and vehicle speed signal, so as to assist driving or brake kinetic energy recovery; A primary reducer (600) synchronously connects the ring gears of the first planetary gear device (200) and the second planetary gear device (400); The secondary speed reducer (700) and the differential (800) are used to drive the transmission mechanism of the vehicle.

2. A power split hybrid device according to claim 1, characterized in that: It also includes a control system for intelligently switching driving modes according to the vehicle's driving conditions, controlling the power generation frequency and voltage of the first motor (300) in real time, and adjusting the engine speed and the power output of the second motor (500); the control system includes a motor control unit, a battery management unit, an inverter control unit, an analog quantity conditioning unit, and a digital switch quantity conditioning unit.

3. A control method for a power split hybrid device according to claim 2, characterized in that: Includes the following: When the battery power is higher than a set minimum value, the second motor (500) provides pure electric driving force, the engine (100) does not start working, and the second motor (500) controls vehicle driving according to an accelerator pedal opening signal and a vehicle speed signal; When the battery power is lower than a set minimum value, the engine (100) starts, outputs the main driving force through the planetary carrier of the first planetary gear device (200), the first motor (300) adjusts the engine (100) speed by controlling the power generation frequency and voltage to keep it running at the highest efficiency point, and the second motor (500) controls power generation or driving according to the accelerator pedal opening signal and the vehicle speed signal until the battery power is higher than the set hybrid maximum power and then switches to a pure electric operation mode; When the accelerator or brake is released, the second motor (500) enters a power generation mode, converts the kinetic energy of the vehicle into electrical energy through the second planetary gear device (400), and stores it in the battery; When the battery power level continues to drop to 5% below the set minimum power level, the first motor (300) increases the engine (100) speed by controlling the power generation frequency and voltage to maintain a higher power output, and the second motor (500) controls power generation or driving according to the accelerator pedal opening signal and the vehicle speed signal, but its maximum power is subject to the power generated by the first generator (200), ensuring that the battery power level does not continue to drop.

4. The control method according to claim 3, characterized in that: When the battery power of the vehicle reaches a set high value, the control system shuts down the engine (100) and switches to a pure electric driving mode at all speeds.

5. The control method according to claim 3, characterized in that: If the battery power level drops to a set minimum value, the control system starts the engine (100), and the power is diverted to the ring gear of the first planetary gear device (200) to drive the vehicle, while the center wheel drives the first motor (300) to generate electricity. The speed of the engine (100) is controlled by the speed of the first motor (300) to keep the speed at the optimal efficiency point, and the second motor (500) determines whether to generate electricity or drive according to the accelerator pedal opening signal and the vehicle speed signal.

6. The control method according to claim 3, characterized in that: The control strategy of the first motor (300) is as follows: the first motor (300) controls the rotation speed of the engine (100) by adjusting the power generation frequency and voltage according to the vehicle speed, thereby ensuring that the engine (100) always runs at the highest efficiency rotation speed point; when the battery power continues to decrease, the power output of the engine (100) is increased by increasing the rotation speed of the engine (100); the engine (100) controls the fuel injection amount according to the output torque at the best efficiency point at the running speed, thereby controlling the power output.

7. The control method according to claim 6, characterized in that: The engine (100) outputs power through the planetary carrier of the first planetary gear device (200), and drives the vehicle and the first motor (300) to generate electricity at the same time. The first motor (300) controls the speed of the engine (100) by adjusting the power generation frequency and voltage to ensure that it always runs at the highest efficiency point. The specific power distribution relationship formula is as follows: The rotation speed n1 of the first motor (300) and the rotation speed n1 of the engine (100) f , the rotation speed n of the ring gear of the first planetary gear device (200) related to the vehicle speed q , the reduction ratio i1 of the first planetary gear device (200) is: n1=n f +i1 (n f -n q , The ring gear output torque M of the first planetary gear device (200) q With engine (100) torque M f The relationship is: The torque M1 of the first motor (300) and the torque M of the engine (100) f The relationship is:

8. The control method according to claim 3, characterized in that: The control system optimizes the output torque or energy recovery intensity of the second motor (500) according to different driving modes, based on the throttle opening signal and the energy recovery coefficient, and the second motor (500) dynamically adjusts the output mode according to the real-time working conditions, including: Driving mode: providing auxiliary driving force and driving the vehicle in coordination with the engine (100); Power generation mode: Recover kinetic energy during braking and convert it into electrical energy and store it in the battery.

9. The control method according to claim 3 or 8, characterized in that: The control system intelligently switches between pure electric mode and hybrid mode according to the battery power: When the battery power is higher than a set value, the pure electric mode is prioritized, and the second motor (500) independently drives the vehicle; When the battery power is lower than a set value, the hybrid mode is switched to, and the engine (100) and the second motor (500) work in coordination; When the battery power level is less than 5% of the set minimum power level, the control system increases the engine (100) speed to increase the engine output power, while limiting the output power of the second motor (500) to prevent the battery power level from continuing to decrease.

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