Series-parallel hybrid power driving system and method for diesel tractor

Abstract

The invention provides a series-parallel hybrid power driving system and method for a diesel tractor, and belongs to the field of power transmission and control. The system comprises a first generator, a second generator, a PTO shaft, a storage battery, a first gear set, a second gear set, a third gear set, a planetary gear assembly and an engine; the output shaft of the first generator supports and drives the PTO shaft to work through the second gear set; the output end of the engine supports and drives the PTO shaft to work through the first gear set; the output end of the second motor is connected with a gear ring of the planetary gear assembly, and a sun gear of the planetary gear assembly supports and drives the PTO shaft through a third gear set; according to the series-parallel hybrid electric vehicle, the fuel economy and the dynamic property of the series-parallel hybrid electric vehicle are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of power transmission and control, and in particular to a series-parallel hybrid power driving system and method for a diesel tractor. Background Art

[0002] With the continuous advancement of agricultural modernization, agricultural machinery modernization has become an indispensable part of it. As a key carrier for realizing agricultural technology integration and large-scale application, agricultural machinery equipment is of great significance to the development of modern agriculture and ensuring food security. Faced with the dilemma that existing technologies have not yet achieved key breakthroughs in manufacturing processes and electromechanical and hydraulic integration development capabilities, the rapid development of new energy powertrain technology has provided new, effective and feasible technical ideas for solving the "bottleneck" problem of agricultural machinery transmission systems.

[0003] At present, there is a lack of development of diesel hybrid tractors in the tractor field. Limited by the funding issues of agricultural tractors, hybrid agricultural machinery has the following problems:

[0004] 1. The maximum speed of the drive motor is low, the peak torque is large, and the motor cost is too high;

[0005] 2. Unlike passenger cars, hybrid agricultural machinery is rarely equipped with charging stations in the working areas, so it is not suitable to use plug-in technology for charging. Summary of the invention

[0006] To solve the above problems, the present invention provides a series-parallel hybrid power drive system and method for a diesel tractor. The present invention adds a clutch and a pair of gears at the engine end on the basis of the series-parallel hybrid power configuration, which effectively improves the fuel economy and power of the series-parallel hybrid power vehicle, specifically including:

[0007] A series-parallel hybrid power drive system for a diesel tractor, comprising: a first generator, a second generator, a PTO shaft, a first gear set, a second gear set, a third gear set, a planetary gear assembly and an engine;

[0008] The output shaft of the first generator drives the PTO shaft to work through the second gear set;

[0009] The output end of the engine drives the PTO shaft to work through the first gear set;

[0010] The output end of the second motor is connected to the ring gear of the planetary gear assembly, and the sun gear of the planetary gear assembly drives the PTO shaft through the third gear set;

[0011] The battery provides electric power to the first generator and the second generator.

[0012] The system also includes a first clutch and a second clutch;

[0013] The first clutch is used to control the start and stop of the engine;

[0014] The second clutch is used to control the opening and closing of the PTO shaft.

[0015] A series-parallel hybrid power driving method for a diesel tractor, applied to the series-parallel hybrid power driving system for a diesel tractor, comprises:

[0016] The parallel-parallel hybrid power drive system for a diesel tractor selects a working mode according to working condition requirements, and the working modes include:

[0017] The first hybrid mode, the second hybrid mode, the third hybrid mode, the pure electric mode, the parking charging mode and the engine ignition start mode.

[0018] Preferably, when the power demanded by the PTO shaft + the power demanded by the wheel end for the engine is less than 20% of the rated power of the engine, and the power level of the battery is less than 100%, the first hybrid power mode is supported;

[0019] When the engine speed is greater than 3.14 of the speed of the planetary carrier in the planetary gear assembly, and the second motor needs to be reversed, the second hybrid mode is supported;

[0020] When the engine is on the optimal power curve of the engine, or the engine is operating near the optimal power curve of the engine; and when the battery power is less than 100%, the third hybrid mode is supported;

[0021] When the battery power is greater than 70% and the current power demand reaches 80% or more of the engine rated power, the pure electric mode can be selected;

[0022] When the battery power is less than 100%, the parking charging mode is supported;

[0023] When the engine ignition is started, switch to the engine ignition start mode.

[0024] Preferably, when the working mode is the first hybrid mode:

[0025] The first clutch is engaged, the engine is split through the first gear assembly, a part of the power of the engine is transmitted to the PTO shaft and the battery, and another part of the power of the engine is transmitted to the sun gear of the planetary gear assembly through the third gear assembly;

[0026] The first generator is idling without load, and the battery stores the surplus electric energy transmitted by the engine through the second gear assembly;

[0027] The second generator is transmitted to the ring gear through a gear pair, and the speed is coupled with the engine power flow at the planetary gear, and the final torque and speed are output through the planetary gear.

[0028] Preferably, when the working mode is the second hybrid mode:

[0029] The first clutch is engaged, the engine is started and split through the first gear assembly, a part of the power of the engine is coupled with the power of the first generator and transmitted to the PTO shaft, and another part of the power of the engine is transmitted to the sun gear of the planetary gear assembly;

[0030] The second generator recovers surplus electric energy through the planetary gear assembly and stores the surplus electric energy in the battery.

[0031] Preferably, when the working mode is the third hybrid mode:

[0032] The first clutch is engaged;

[0033] If the first generator is in an unloaded state, the engine is started and diverted through the first gear assembly, a portion of the kinetic energy of the engine is diverted through the first gear assembly to drive the PTO shaft to work, another portion of the power of the engine is diverted through the planetary gear assembly, a portion of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another portion of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly;

[0034] If the first generator is in a power generation state, the engine is started and diverted through the first gear assembly, a portion of the power of the engine is diverted to the PTO shaft and the first generator through the first gear assembly, the first generator generates electricity through the received power, the PTO shaft works through the received power, another portion of the power of the engine is diverted through the planetary gear assembly, a portion of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another portion of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly.

[0035] Preferably, when the working mode is pure electric mode:

[0036] The first clutch is in a disconnected state, the first generator is in a generating state and drives the PTO shaft to work;

[0037] The second generator is disconnected and the rotor of the second generator is floated.

[0038] Preferably, when the working mode is the parking charging mode:

[0039] The first clutch is in a connected state, the engine is started, the battery is in a charged state, the second generator is disconnected, and the rotor of the second generator is floating.

[0040] Preferably, when the working mode is the engine ignition start mode:

[0041] The first generator outputs power, the second generator is not connected, the first clutch is connected, and the second clutch is not connected.

[0042] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0043] The working efficiency of the diesel engine is improved, and the power and fuel consumption of the tractor using the hybrid power configuration are improved. The system can output the engine and dual-motor hybrid power, which not only effectively improves the power and fuel economy of the tractor, but also can use the diesel engine to charge the battery, solving the charging problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 is a schematic diagram of a system of the present invention;

[0046] Figure 2 is a schematic diagram of a first hybrid power mode of the present invention;

[0047] Figure 3 is a schematic diagram of a second hybrid power mode of the present invention;

[0048] Figure 4 is a schematic diagram of a third hybrid power mode of the present invention;

[0049] Figure 5 This is a schematic diagram of a pure electric mode of the present invention;

[0050] Figure 6 This is a schematic diagram of the parking charging mode of the present invention;

[0051] Figure 7 It is a schematic diagram of the engine ignition start mode of the present invention;

[0052] Figure 8 It is a schematic diagram of the braking recovery mode of the present invention.

[0053] In the figure:

[0054] M1-first generator; M2-second generator;

[0055] PTO-PTO shaft;

[0056] C1-first clutch; C2-second clutch;

[0057] i1-first gear set, i2-second gear set; i3-third gear set;

[0058] C-planet carrier inside the planetary gear assembly; S-sun gear inside the planetary gear assembly; R-ring gear inside the planetary gear assembly. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "one" or "the" do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0061] It should be noted that the terms "up", "down", "left", "right", "front" and "back" used in the present invention are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0062] like Figures 1 to 8As shown, the present invention provides a series-parallel hybrid power drive system for a diesel tractor in a first aspect, comprising: a first generator, a second generator, a PTO shaft, a first gear set, a second gear set, a third gear set, a planetary gear assembly and an engine; in the present application, the specific structures of the first generator, the second generator, the PTO shaft, the first gear set, the second gear set, the third gear set, the planetary gear assembly and the engine are prior art and will not be elaborated in the present application.

[0063] The system of the present application mainly adds a clutch and a pair of gears on the engine end based on the series-parallel hybrid configuration of the prior art (a multi-mode series-parallel hybrid vehicle drive system with patent publication number CN117698403A), which effectively improves the fuel economy and power of the series-parallel hybrid vehicle.

[0064] The output shaft of the first generator supports driving the PTO shaft through the second gear set; the output end of the engine supports driving the PTO shaft through the first gear set; the output end of the second motor is connected to the ring gear of the planetary gear assembly, and the sun gear of the planetary gear assembly supports driving the PTO shaft through the third gear set.

[0065] The system also includes a first clutch and a second clutch; the first clutch is used to control the start and stop of the engine; the second clutch is used to control the start and stop of the PTO shaft.

[0066] In this system, the hybrid power configuration combines the advantages of the series and parallel configurations. Through the coupling of different energy sources, the transmission system can have higher driving efficiency and energy utilization. And due to the existence of the planetary gear set, the size and mass of each component are relatively small. Therefore, based on the above analysis, considering the complex and changeable working conditions of the tractor, a hybrid power system configuration scheme is proposed.

[0067] The system is composed of an engine, a first generator and a second generator, a planetary gear set and several gear sets (first gear set, second gear set and third gear set). The two generators are mainly driven by the engine to generate electricity, and secondly can be used for braking energy recovery and engine starting. The second generator can be coupled with the power transmitted by the engine and the first generator in the planetary gear set for output.

[0068] The driving torque of a hybrid tractor needs to remain constant under various working conditions, and the speed needs to be changed according to requirements. The purpose of the hybrid configuration is to ensure that the engine can still operate in an efficient working range under different conditions, thereby improving the engine's fuel economy and power.

[0069] Based on the above requirements, the hybrid system in this paper adopts a parallel-parallel transmission, and the power coupling device is a single planetary gear and a gear pair. The parallel-parallel transmission of dual motors and engines can achieve the purpose of the engine driving the motor to generate electricity and coupling with the motor to output power, as well as improving the working efficiency of the engine, and adapting to different working conditions.

[0070] The hybrid power system designed in this system can realize parallel and hybrid switching. In the first hybrid power mode, after the engine power is split, part of it is output to the PTO shaft or the PTO shaft and the first generator, and part of it is output to the output shaft after the convergence speed coupling with the second generator in the planetary gear. This mode can realize parallel and hybrid switching. If the first generator is idling without load, this mode is parallel transmission. At this time, the final speed is obtained by the superposition of the engine and the second generator speed coupling. The torque of the engine and the second generator is in a certain proportion. The engine torque is uncontrollable but the speed is controllable, and it can work in the high-efficiency range. If the first generator is working in a charging state, the mode is hybrid.

[0071] In the second hybrid power mode, a part of the engine power is diverted to the first motor for torque coupling to drive the PTO shaft, and the other part is diverted to the planetary gear and output to the second generator and the output shaft. At this time, the system is a hybrid transmission.

[0072] The third hybrid mode can realize the switching between parallel transmission and hybrid transmission like the first hybrid mode. After the engine power is diverted by the gear pair, part of it drives the PTO shaft to work or drives the PTO shaft and the first generator to generate electricity, and part of it is diverted by the planetary gear to the second generator and the output shaft. If the first generator is idling without load, this mode is parallel transmission. If the first generator is working in the charging state, this mode is hybrid.

[0073] In pure electric mode, the engine is turned off and the first clutch is disconnected, the first generator outputs power to the shaft, the second generator is not powered, and the rotor floats, so that the PTO low-power operation can be achieved when the tractor is in pure electric parking. The above three hybrid modes can control the engine to operate in the high-efficiency working range under various working conditions.

[0074] In a second aspect, the present invention provides a series-parallel hybrid power driving method for a diesel tractor, which is applied to the series-parallel hybrid power driving system for a diesel tractor, comprising:

[0075] The parallel-parallel hybrid power drive system for a diesel tractor selects a working mode according to working condition requirements, and the working modes include:

[0076] The first hybrid mode, the second hybrid mode, the third hybrid mode, the pure electric mode, the parking charging mode and the engine ignition start mode.

[0077] In a specific implementation mode, when the power required by the PTO shaft + the power required by the wheel end for the engine is less than 20% of the rated power of the engine, and the power of the battery is less than 100%, the first hybrid power mode is supported;

[0078] When the engine speed is greater than 3.14 of the speed of the planetary carrier in the planetary gear assembly, and the second motor needs to be reversed, the second hybrid mode is supported;

[0079] When the engine is on the optimal power curve of the engine, or the engine is operating near the optimal power curve of the engine; and when the battery power is less than 100%, the third hybrid mode is supported;

[0080] When the battery power is greater than 70% and the current power demand reaches 80% or more of the engine rated power, the pure electric mode can be selected;

[0081] When the battery power is less than 100%, the parking charging mode is supported;

[0082] When the engine ignition is started, switch to the engine ignition start mode.

[0083] In a specific implementation manner, when the working mode is the first hybrid power mode:

[0084] When the sum of the power required by the PTO shaft and the power required by the wheel end for the engine is less than 20% of the rated power of the engine and the battery power is not 100%, switching can be performed, and the first hybrid mode can be selected at this time.

[0085] In the first hybrid power mode, the first clutch is connected, the engine is diverted through the first gear assembly, part of the power of the engine is transmitted to the PTO shaft and the battery, and the other part of the power of the engine is transmitted to the sun gear of the planetary gear assembly through the third gear assembly; the first generator is idling at no load, and the battery stores the surplus electric energy transmitted by the engine through the second gear assembly; the second generator is transmitted to the ring gear through the gear pair, and the speed is coupled with the engine power at the planetary row, and the final torque and speed are output through the planetary gear.

[0086] In the first hybrid mode, the first generator can be idling without load or working in the power generation state, and the battery discharges to supply power to the second generator. The engine is started and the first clutch is connected. At this time, the power of the engine is divided through the gear pair, part of which is transmitted to the PTO shaft or the PTO shaft and the first generator, and the other part of the power is transmitted to the sun gear of the planetary gear (planetary gear assembly). When the first generator is idling without load, the power of the second generator is transmitted to the ring gear through the gear pair, and the speed is coupled with the engine power at the planetary gear, and the final torque and speed are output through the planetary gear. This mode belongs to the parallel speed coupling hybrid mode, and the working state of the first generator is determined according to the load condition. If the load is large, the first generator works in the power generation state and supplies power to the second generator together with the battery. This mode is suitable for the working conditions of the tractor with low power and high speed, such as low load work such as tractor sowing. Adjusting the second generator can keep the engine working in the high efficiency area.

[0087] When the working mode is the second hybrid mode: when the engine speed is greater than 3.14 times the planetary carrier speed, the second generator needs to reverse to support the selection of the second hybrid mode.

[0088] In the second hybrid power mode: the first clutch is engaged, the engine is started and diverted through the first gear assembly, a portion of the power of the engine and the power of the first generator are torque-coupled and transmitted to the PTO shaft, and another portion of the power of the engine is transmitted to the sun gear of the planetary gear assembly; the second generator recovers surplus electric energy through the planetary gear assembly and stores it in the battery.

[0089] In the second hybrid mode, the engine is started, and its power is divided through the gear pair. A part of the power is coupled with the first generator for torque and then output to the PTO shaft, and the other part is transmitted to the planetary sun gear. Different from the first hybrid mode, the first generator acts as a drive motor. The battery discharges to power the first generator.

[0090] After the engine power is split again by the planetary gear, part of it is transferred to the second generator through the ring gear for power generation, and the other part is output through the planetary gear for the final torque and speed. The working state of the first generator can be changed according to the load condition. For example, when the load is too large and the battery power supply is insufficient, the second generator and the battery will supply power to the first generator together; if the load is small, the surplus energy after the second generator generates power is stored in the battery.

[0091] This hybrid mode belongs to the series-parallel hybrid mode and is suitable for working conditions where the tractor is traveling at low speed and the workload varies greatly, such as tractor plowing. By adjusting the first generator, the engine can work at the optimal working point without being affected by the working conditions.

[0092] When the working mode is the third hybrid mode: when the engine is working at 10% near the optimal power curve and the battery power is not 100%, it can be switched to the third hybrid mode.

[0093] In the third hybrid power mode: the first clutch is engaged; if the first generator is in an unloaded state, the engine is started and diverted through the first gear assembly, a part of the kinetic energy of the engine is diverted through the first gear assembly to drive the PTO shaft to work, another part of the power of the engine is diverted through the planetary gear assembly, a part of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another part of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly; if the first generator is in a power generation state, the engine is started and diverted through the first gear assembly, a part of the power of the engine is diverted to the PTO shaft and the first generator through the first gear assembly, the first generator generates electricity through the received power, the PTO shaft works through the received power, another part of the power of the engine is diverted through the planetary gear assembly, a part of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another part of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly.

[0094] In the third hybrid mode, the first generator can work in the power generation state or no-load idling as in the first hybrid mode. The engine is started and the first clutch is connected. At this time, the power of the engine is split through the gear pair, part of which is transmitted to the PTO shaft or the PTO shaft and the first generator, and the other part of the power is transmitted to the sun gear of the planetary gear. When the first generator is idling, the engine power is split through the gear pair, and part of the power drives the PTO shaft to work. The second generator works in the power generation state. After the engine power is split again in the planetary gear, part of the power is transmitted to the second generator through the ring gear for power generation, and the other part of the power is output through the planetary gear for the final torque and speed. The battery works in the charging state and is charged by the second generator. This mode belongs to the parallel hybrid mode. When the first generator works in the power generation state, the engine power is split through the gear pair and partly transmitted to the PTO shaft and the first generator, driving the PTO shaft to work and driving the first generator to generate electricity at the same time. At this time, the battery is charged by the second generator and the first generator together. This mode can realize the switching between parallel and hybrid modes, improve the utilization of engine power, and is suitable for the low-power operation of PTO when the tractor is running at low speed.

[0095] When the working mode is pure electric mode: the pure electric mode can be switched when the battery power is greater than 70% and the current required power reaches 80% of the engine rated power.

[0096] In the pure electric mode: the first clutch is in the disconnected state, the first generator is in the generating state and drives the PTO shaft to work; the second generator is disconnected, and the rotor of the second generator floats.

[0097] In pure electric mode, the engine is turned off and the first clutch is disconnected. The second generator is not powered and the rotor is floating. The first generator acts as a drive motor to output power, and the battery supplies power to the first generator. The power of the first generator is diverted to the PTO shaft and the planetary sun gear through the gear pair, so the PTO can perform certain light load work. The output shaft does not work. This mode is suitable for the tractor in the pure electric state when it is parked, allowing the PTO to undertake certain light load work.

[0098] When the working mode is parking charging mode:

[0099] The first clutch is in the connected state, the engine is started, the battery is in the charging state, the second generator is disconnected, and the rotor of the second generator is floating. In this mode, the battery is in the charging mode and is charged by the first generator. The engine is started, the first clutch is connected, and the second clutch is disconnected. The first generator acts as a generator, driven by the power diverted from the engine to generate electricity, and the PTO shaft can also perform certain light-load work. The second generator is not powered, and the rotor is floating. This mode is suitable for tractor parking and charging, and can allow the PTO to undertake certain light-load work during charging.

[0100] When the working mode is engine ignition start mode:

[0101] The first generator outputs power, the second generator is not connected, the first clutch is connected, and the second clutch is not connected. In this mode, the first generator outputs power. The battery supplies power to the first generator. The second generator is not powered, and the rotor floats. The first clutch is connected, and the second clutch is disengaged. At this time, the power output by the first generator is input to the engine through the gear pair to provide it with the torque required for starting. This mode is suitable for engine starting to reduce fuel consumption during engine starting.

[0102] The method also includes a braking recovery mode, in which the second generator is in a power generation state or the first generator and the second generator are in a power generation state at the same time, and the battery is in a charging state. The braking energy is input to the planetary gear through the output shaft for diversion. Part of the energy drives the second generator to generate electricity through the ring gear. The other part of the energy is diverted again through the gear pair and transferred to the first generator and the engine. Part of the secondary diverted energy provides braking torque for the engine, and the other part can also drive the first generator to charge the battery. This mode is suitable for recovering braking energy when the tractor brakes.

[0103] Table 1: Working status of each component in each mode:

[0104] Table-1

[0105]

[0106] The system and method improve the working efficiency of the diesel engine and improve the power and fuel consumption of the tractor using the hybrid power configuration. The configuration can output the hybrid power of the engine and the dual motors, which not only effectively improves the power and fuel economy of the tractor, but also can use the diesel engine to charge the battery, solving the charging problem.

[0107] The following points need to be explained:

[0108] (1) The drawings of the embodiments of the present invention only involve structures related to the embodiments of the present invention. Other structures may refer to conventional designs.

[0109] (2) For the sake of clarity, in the drawings used to describe the embodiments of the present invention, the thickness of layers or regions is exaggerated or reduced, that is, these drawings are not drawn according to the actual scale. It is understood that when an element such as a layer, film, region or substrate is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element or there may be intermediate elements.

[0110] (3) In the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0111] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A series-parallel hybrid power drive system for a diesel tractor, characterized in that: include: a first generator, a second generator, a PTO shaft, a battery, a first gear set, a second gear set, a third gear set, a planetary gear assembly, and an engine; The output shaft of the first generator drives the PTO shaft to work through the second gear set; The output end of the engine drives the PTO shaft to work through the first gear set; The output end of the second motor is connected to the ring gear of the planetary gear assembly, and the sun gear of the planetary gear assembly drives the PTO shaft through the third gear set; The battery provides electric power to the first generator and the second generator.

2. The series-parallel hybrid power drive system for a diesel tractor according to claim 1, further comprising a first clutch and a second clutch; The first clutch is used to control the start and stop of the engine; The second clutch is used to control the opening and closing of the PTO shaft.

3. A parallel-parallel hybrid power driving method for a diesel tractor, characterized in that: The parallel-parallel hybrid power drive system for a diesel tractor as described in claims 1 to 2 comprises: The parallel-parallel hybrid power drive system for a diesel tractor selects a working mode according to working condition requirements, and the working modes include: The first hybrid mode, the second hybrid mode, the third hybrid mode, the pure electric mode, the parking charging mode and the engine ignition start mode.

4. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the power demanded by the PTO shaft + the power demanded by the wheel end for the engine is less than 20% of the rated power of the engine, and the battery power is less than 100%, the first hybrid power mode is supported; When the engine speed is greater than 3.14 of the speed of the planetary carrier in the planetary gear assembly, and the second motor needs to be reversed, the second hybrid mode is supported; When the engine is on the optimal power curve of the engine, or the engine is operating near the optimal power curve of the engine; and; the battery power is less than 100%, supporting the selection of the third hybrid mode; When the battery power is greater than 70% and the current power demand reaches 80% or more of the engine rated power, the pure electric mode can be selected; When the battery power is less than 100%, the parking charging mode is supported; When the engine ignition is started, switch to the engine ignition start mode.

5. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is the first hybrid mode: The first clutch is engaged, the engine is split through the first gear assembly, a part of the power of the engine is transmitted to the PTO shaft and the battery, and another part of the power of the engine is transmitted to the sun gear of the planetary gear assembly through the third gear assembly; The first generator is idling without load, and the battery stores the surplus electric energy transmitted by the engine through the second gear assembly; The second generator is transmitted to the ring gear through a gear pair, and the speed is coupled with the engine power flow at the planetary gear, and the final torque and speed are output through the planetary gear.

6. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is the second hybrid mode: The first clutch is engaged, the engine is started and split through the first gear assembly, a part of the power of the engine is coupled with the power of the first generator and transmitted to the PTO shaft, and another part of the power of the engine is transmitted to the sun gear of the planetary gear assembly; The second generator recovers surplus electric energy through the planetary gear assembly and stores the surplus electric energy in the battery.

7. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is the third hybrid mode: The first clutch is engaged; If the first generator is in an unloaded state, the engine is started and diverted through the first gear assembly, a portion of the kinetic energy of the engine is diverted through the first gear assembly to drive the PTO shaft to work, another portion of the power of the engine is diverted through the planetary gear assembly, a portion of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another portion of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly; If the first generator is in a power generation state, the engine is started and diverted through the first gear assembly, a portion of the power of the engine is diverted to the PTO shaft and the first generator through the first gear assembly, the first generator generates electricity through the received power, the PTO shaft works through the received power, another portion of the power of the engine is diverted through the planetary gear assembly, a portion of the power diverted by the planetary gear assembly drives the second generator to generate electricity through the ring gear of the planetary gear assembly, and another portion of the power diverted by the planetary gear assembly outputs the final torque and speed through the planetary gear of the planetary gear assembly.

8. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is pure electric mode: The first clutch is in a disconnected state, the first generator is in a generating state and drives the PTO shaft to work; The second generator is disconnected and the rotor of the second generator is floated.

9. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is parking charging mode: The first clutch is in a connected state, the engine is started, the battery is in a charged state, the second generator is disconnected, and the rotor of the second generator is floating.

10. The parallel-parallel hybrid power driving method for a diesel tractor according to claim 3, characterized in that: When the working mode is engine ignition start mode: The first generator outputs power, the second generator is not connected, the first clutch is connected, and the second clutch is not connected.

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