Diesel DCT power assembly resonance optimization method and system

Abstract

The invention discloses a diesel DCT power assembly resonance optimization method and system, relates to the technical field of power assembly simulation testing, and aims to solve the problem that the engine speed lasts for a long time in a resonance speed interval of a dual-mass flywheel due to insufficient combustion in a cylinder and low output power of a diesel engine under a low-temperature cold start working condition. The starting strategy of the diesel engine is optimized, so that the power source of the diesel DCT power assembly overcomes the resistance source of the diesel DCT power assembly, and then the starting rotating speed of the diesel engine can quickly pass through the resonance interval of the dual-mass flywheel; by the adoption of the resonance optimization method, resonance generated by a power system with the diesel engine and the DCT gearbox matched with each other during low-temperature cold start can be effectively reduced, and the engine rotating speed can be prevented from being kept within the resonance rotating speed interval of the dual-mass flywheel all the time when the engine is started. And the service life of main parts in the power assembly can be prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of powertrain simulation testing, and in particular to a diesel DCT powertrain resonance optimization method and system. Background Art

[0002] In the automotive field, there are various powertrain combinations, such as front-wheel drive gasoline engines matched with manual transmissions and various automatic transmissions (including AT\CVT\DCT), and front-wheel drive diesel engines matched with manual transmissions and various automatic transmissions (including AT); but currently there are few front-wheel drive diesel engines matched with wet dual-clutch transmissions (wet DCT) in the Chinese market. Therefore, cold start research related to powertrains of diesel engines matched with dual-mass flywheels and wet DCT is relatively rare, and there are not many studies in the foreign automotive field. In models matched with dual-mass flywheels (DMF), avoiding the excitation of DMF resonance when the engine starts has always been a key research direction in the automotive field. For a powertrain combination of a diesel engine matched with a dual-mass flywheel and a wet dual-clutch transmission, this problem is particularly prominent. At present, there are also similar patents for studying DMF resonance, which reveal the resonance detection method of the dual-mass flywheel and the avoidance of dual-mass flywheel resonance through engine software control.

[0003] However, the combustion method of diesel engines is different from that of gasoline engines. Diesel engines mainly perform work through compression ignition. When diesel engines are cold-started at low temperatures, the ambient temperature and the temperature in the cylinder are relatively low, the combustion efficiency during compression ignition is relatively low, and the combustion in the engine cylinder is not complete, resulting in less output torque during cold start of the engine. At the same time, the battery capacity decreases under low temperature conditions, affecting the starting power of the starter (current and voltage at start-up), resulting in a smaller output torque of the starter. At this time, the engine oil and the transmission oil of the wet dual-clutch transmission have a large drag torque under low temperature conditions.

[0004] Therefore, in the prior art, while fully considering the low-temperature cold start condition, how to make the engine speed quickly pass through the DMF resonance speed range to avoid the engine speed being in the DMF resonance speed range for a long time, causing violent resonance of the entire transmission system and irreversible damage to various components has become a problem that needs to be urgently solved in the industry. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a diesel DCT powertrain resonance optimization method and system, which aims to adjust and optimize the starting strategy of the diesel engine so that the engine speed can quickly cross the DMF resonance speed range and reduce resonance, thereby solving the problems recorded in the prior art.

[0006] A first aspect of the present invention is to provide a diesel DCT powertrain resonance optimization method, the method comprising:

[0007] Obtain the starting speed and oil resistance of the diesel engine during cold start, and output a starting speed-oil resistance curve according to the starting speed and oil resistance;

[0008] Obtain the drag torque of the gearbox in the parking gear when the diesel engine is cold started, and determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque;

[0009] Obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel;

[0010] Obtaining cylinder pressure data of the diesel engine, outputting engine output torque corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine the maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve;

[0011] The maximum resistance source torque curve and the maximum power source torque curve are fitted to obtain the difference comparison curve between the resistance source and the power source at different speeds of the diesel engine;

[0012] The first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started is calculated through CAE simulation, and the second-order resonant speed of the diesel DCT powertrain is calculated based on the first-order torsional vibration frequency;

[0013] Combined with CAE simulation, the resonant speed range of the second-order resonant speed is determined according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonant speed range.

[0014] According to one aspect of the above technical solution, the steps of combining CAE simulation and determining the resonance speed range of the second-order resonance speed according to the difference comparison curve to optimize the start-up strategy of the diesel DCT powertrain according to the resonance speed range include:

[0015] Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined;

[0016] According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

[0017] According to one aspect of the above technical solution, the calculation expression of the resonance frequency is:

[0018]

[0019] The calculation expression of the resonant speed is:

[0020] n = 60f;

[0021] Where f is the resonant frequency, K is the system stiffness, M is the system moment of inertia, and n is the resonant speed.

[0022] According to one aspect of the above technical solution, the steps of obtaining the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determining the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque include:

[0023] Connect the diesel engine to the DCT gearbox and arrange it on the bench equipment;

[0024] Bench test of the DCT transmission to test the drag torque of the DCT transmission in the parking gear position during cold start of the diesel engine;

[0025] According to the starting speed-oil resistance curve and the drag torque, the maximum resistance source torque curve of the diesel DCT powertrain is determined.

[0026] According to one aspect of the above technical solution, the steps of obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel include:

[0027] Monitor the starting voltage and starting current of the starter;

[0028] According to the starting voltage and starting current of the starter, the output power and output torque of the starter corresponding to different engine speeds during cold start are obtained;

[0029] According to the output power and output torque of the starter, the starter speed-output torque curve is output;

[0030] Obtaining a transmission ratio between a drive ring gear in a starter and a signal ring gear in a dual mass flywheel;

[0031] According to the transmission ratio between the driving ring gear in the starter and the signal ring gear in the dual mass flywheel, the ring gear output torque of the signal ring gear in the dual mass flywheel is output.

[0032] According to one aspect of the above technical solution, the steps of calculating the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started by CAE simulation and calculating the second-order resonant speed of the diesel DCT powertrain according to the first-order torsional vibration frequency include:

[0033] The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during the diesel engine startup process is calculated through CAE simulation;

[0034] Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system;

[0035] The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

[0036] According to one aspect of the above technical solution, after optimizing the startup strategy of the diesel DCT powertrain, the method further includes:

[0037] The speed information of the crankshaft position sensor is collected through the data collection terminal to identify the engine starting speed of the diesel engine;

[0038] It is determined whether the engine starting speed exceeds the resonance speed range of the second-order resonance speed within a preset time.

[0039] The second aspect of the present invention is to provide a diesel DCT powertrain resonance optimization system, which is applied to the method described in the above technical solution, and the system comprises:

[0040] The first processing module is used to obtain the starting speed and oil resistance of the diesel engine during cold start, and output a starting speed-oil resistance curve according to the starting speed and oil resistance;

[0041] The second processing module is used to obtain the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque;

[0042] In the third processing module, the user obtains the output power and output torque of the starter corresponding to different engine speeds, obtains the starter speed-output torque curve, and outputs the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel;

[0043] a fourth processing module, for obtaining cylinder pressure data of the diesel engine, outputting engine output torques corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine a maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve;

[0044] A curve fitting module is used to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve between the resistance source and the power source at different speeds of the diesel engine;

[0045] A simulation calculation module is used to calculate the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started through CAE simulation, and calculate the second-order resonant speed of the diesel DCT powertrain based on the first-order torsional vibration frequency;

[0046] The resonance optimization module is used to determine the resonance speed range of the second-order resonance speed in combination with the CAE simulation and according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonance speed range.

[0047] According to one aspect of the above technical solution, the simulation calculation module is specifically used for:

[0048] The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during the diesel engine startup process is calculated through CAE simulation;

[0049] Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system;

[0050] The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

[0051] According to one aspect of the above technical solution, the resonance optimization module is specifically used for:

[0052] Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined;

[0053] According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

[0054] Compared with the prior art, the diesel DCT power system resonance optimization method and system shown in the present invention have the following beneficial effects:

[0055] The present invention proposes for the first time a power system in which a diesel engine and a DCT gearbox are matched with each other. Since the diesel engine has incomplete combustion in the cylinder under low-temperature cold start conditions and the output power is small, the engine speed lasts for a long time in the resonant speed range of the dual-mass flywheel. The present invention optimizes the starting strategy of the diesel engine so that the power source of the diesel DCT powertrain overcomes the resistance source of the diesel DCT powertrain, thereby enabling the starting speed of the diesel engine to quickly pass through the resonance range of the dual-mass flywheel to avoid the engine speed being maintained in the resonant speed range of the dual-mass flywheel when the engine is started. The resonance optimization method shown in the present invention can effectively reduce the resonance generated by the power system in which the diesel engine and the DCT gearbox are matched with each other during low-temperature cold start, which is beneficial to improving the service life of the main components in the powertrain. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0057] Figure 1 It is a schematic flow chart of a method for optimizing the resonance of a diesel DCT powertrain according to an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of the structure of a diesel DCT powertrain in one embodiment of the present invention;

[0059] Figure 3 A schematic diagram of a diesel engine speed-oil resistance curve during a low-temperature cold start in one embodiment of the present invention;

[0060] Figure 4 A schematic diagram of a starter speed-output torque curve during low-temperature cold start in one embodiment of the present invention;

[0061] Figure 5 It is a schematic diagram of a diesel engine speed-output torque curve during a low-temperature cold start of the engine in one embodiment of the present invention;

[0062] Figure 6 A schematic diagram of a comparison curve of driving force and resistance during engine starting in one embodiment of the present invention;

[0063] Figure 7 It is a schematic diagram of CAE calculation results of the first-order torsional vibration frequency of the existing DMF scheme and powertrain system;

[0064] Figure 8 It is a schematic diagram of CAE calculation results of the first-order torsional vibration frequency of the powertrain system in a new DMF solution in one embodiment of the present invention;

[0065] Fig. 9It is a structural block diagram of a diesel DCT powertrain resonance optimization system in one embodiment of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. Several embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0068] Embodiment 1

[0069] Figure 1 A schematic diagram of a diesel DCT powertrain resonance optimization method provided by the first embodiment of the present invention is shown in FIG. Figure 2 As shown, it includes a diesel engine 1, a dual-mass flywheel 2, a wet dual clutch 3 (DCT) and a starter 4. When the diesel engine 1 is started at low temperature, the starter 4 first drives the flywheel disc of the dual-mass flywheel 2 to rotate, and then drives the crankshaft of the diesel engine 1 to rotate, and injects fuel into the cylinder through software control to achieve in-cylinder compression ignition, and then drives the dual-mass flywheel 2 and the rear-end wet dual clutch transmission 3 to move.

[0070] The method comprises steps S10 to S70:

[0071] Step S10, obtaining the starting speed and the oil resistance of the diesel engine during cold start, and outputting a starting speed-oil resistance curve according to the starting speed and the oil resistance;

[0072] In this embodiment, if Figure 3 As shown, through the engine bench test, the starting speed-oil resistance curve of the diesel engine during low-temperature cold start is obtained. By finding out how much torque the diesel engine can output at different speeds during the low-temperature cold start process, the resistance of the diesel engine at low oil temperature is obtained.

[0073] Step S20, obtaining the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determining the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque.

[0074] The step of obtaining the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determining the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque includes:

[0075] Connect the diesel engine to the DCT gearbox and arrange it on the bench equipment;

[0076] Bench test of the DCT transmission to test the drag torque of the DCT transmission in the parking gear position during cold start of the diesel engine;

[0077] According to the starting speed-oil resistance curve and the drag torque, the maximum resistance source torque curve of the diesel DCT powertrain is determined.

[0078] In this embodiment, by performing a bench test on the gearbox and testing the drag torque of the gearbox in P gear when the diesel engine is cold started at low temperature, it can be concluded that the maximum drag torque of the gearbox at low temperature is about 13NM. Then, according to the starting speed-oil resistance curve and the drag torque obtained in step S10, the maximum resistance source torque curve of the entire diesel DCT powertrain can be output.

[0079] Step S30, obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel;

[0080] The steps of obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel include:

[0081] Monitor the starting voltage and starting current of the starter;

[0082] According to the starting voltage and starting current of the starter, the output power and output torque of the starter corresponding to different engine speeds during cold start are obtained;

[0083] According to the output power and output torque of the starter, the starter speed-output torque curve is output;

[0084] Obtaining a transmission ratio between a drive ring gear in a starter and a signal ring gear in a dual mass flywheel;

[0085] According to the transmission ratio between the driving ring gear in the starter and the signal ring gear in the dual mass flywheel, the ring gear output torque of the signal ring gear in the dual mass flywheel is output.

[0086] It should be noted here that the dual mass flywheel, namely DMF, stands for Dual Mass Flywheel. Its existence can greatly improve the torsional vibration problem of the engine.

[0087] Specifically, dual-mass flywheels have many different structural forms, which are generally composed of a first mass, a second mass, and a torsional vibration structure in the middle. When the engine is working, power is input to the first mass, driving the first mass to rotate. At this time, since the circumferential spring is connected to the slot on the first mass, the circumferential spring is compressed, and the power is transmitted to the force transmission plate. The force transmission plate is rigidly connected to the second mass, and then the power is transmitted to the input end of the gearbox to complete the power transmission. In essence, through this structural design of the dual-mass flywheel, it is equivalent to cutting the original flywheel into two parts, transmitting through the coil spring in the middle, and then forming a torsional vibration system to achieve the function of vibration isolation.

[0088] In this embodiment, if Figure 4 As shown, by monitoring the starting voltage and starting current of the starter, testing the output power of the starter at different engine speeds under low temperature conditions, and then obtaining the output torque of the starter, the starter speed-output torque curve during low temperature cold start can be obtained; then, based on the transmission ratio between the drive ring gear of the starter and the signal of the dual mass flywheel, the output torque on the signal ring gear of the dual mass flywheel is calculated. In this embodiment, the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel is 1:10, that is, the torque output by the starter is amplified 10 times to obtain the output torque on the signal ring gear of the dual mass flywheel.

[0089] Step S40, obtaining cylinder pressure data of the diesel engine, outputting engine output torques corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine a maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve;

[0090] In this embodiment, if Figure 5 As shown in the figure, the engine output torque at different starting speeds can be obtained by testing the cylinder pressure data on the engine bench, which can show the actual output torque of the diesel engine under low temperature conditions. Figure 4 The diesel engine speed-output torque curve is shown.

[0091] Step S50, fitting the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve between the resistance source and the power source at different speeds of the diesel engine.

[0092] In this embodiment, if Figure 6 As shown, based on the above test data, considering the damping effect of DMF under low temperature conditions, the difference comparison curve of the resistance source and the driving source under different engine speeds can be preliminarily fitted. It can be seen that the driving torque (power source) and the resistance torque (resistance source) are relatively close in a certain speed range. If the resonant speed range of the entire powertrain coincides with this range, it is easy to produce resonance of the dual mass flywheel, that is, the resonance of the entire transmission system. Therefore, in this embodiment, it is necessary to optimize the resonance generated when the diesel engine is cold started, such as optimizing the calibration of the starting speed.

[0093] Step S60, calculating the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started by CAE simulation, and calculating the second-order resonant speed of the diesel DCT powertrain according to the first-order torsional vibration frequency;

[0094] The steps of calculating the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started by CAE simulation and calculating the second-order resonant speed of the diesel DCT powertrain according to the first-order torsional vibration frequency include:

[0095] The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during the diesel engine startup process is calculated through CAE simulation;

[0096] Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system;

[0097] The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

[0098] In this embodiment, the first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, DMF, and DCT gearbox in the engine startup state is calculated by CAE simulation, and then the second-order resonant speed of the entire diesel DCT powertrain is calculated. The second-order resonant speed can be characterized as the DMF resonant speed. It can be seen that the resonant frequency of the entire powertrain of the original DMF scheme in this embodiment is 12.2HZ, which is converted into the second-order resonant speed of the engine of 366rpm. Figure 7 n1 is marked in the figure.

[0099] Step S70 , combining CAE simulation and determining the resonance speed range of the second-order resonance speed according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonance speed range.

[0100] The steps of combining CAE simulation and determining the resonance speed range of the second-order resonance speed according to the difference comparison curve to optimize the start strategy of the diesel DCT powertrain according to the resonance speed range include:

[0101] Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined;

[0102] According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

[0103] The calculation expression of the resonance frequency is:

[0104]

[0105] The calculation expression of the resonant speed is:

[0106] n = 60f;

[0107] Where f is the resonant frequency, K is the system stiffness, M is the system moment of inertia, and n is the resonant speed.

[0108] In this embodiment, after optimizing the startup strategy of the diesel DCT powertrain, the method further includes:

[0109] The speed information of the crankshaft position sensor is collected through the data collection terminal to identify the engine starting speed of the diesel engine;

[0110] It is determined whether the engine starting speed exceeds the resonance speed range of the second-order resonance speed within a preset time.

[0111] In this embodiment, according to the theoretical calculation formula of the resonant frequency and resonant speed, increasing the moment of inertia of the DMF secondary flywheel is beneficial to reducing the resonant speed of the entire powertrain. After the resonant speed drops, the output torque of the starter is greater, and the power source will be greater than the resistance source, which is beneficial for the engine to quickly pass through the DMF resonance range when starting, avoiding the excitation of DMF resonance. Figure 8 In the CAE simulation analysis, it can be seen that by optimizing the rotational inertia of the DMF secondary flywheel, the resonance frequency of the entire powertrain can be reduced to 9HZ, which is converted into the second-order resonance speed of the engine to 270rpm. Figure 8 n2 is marked in the figure. At this time, the resonant speed is reduced to the range of 270rpm, and the driving force at this time is much greater than the resistance; therefore, by optimizing the starting strategy in this embodiment, the diesel DCT powertrain can quickly pass the resonant speed when starting at low temperature, avoiding serious damage to components caused by maintaining the resonant speed range.

[0112] In summary, compared with the prior art, the diesel DCT powertrain resonance optimization method shown in this embodiment has the following beneficial effects:

[0113] This embodiment proposes for the first time a power system in which a diesel engine and a DCT gearbox are matched with each other. Since the diesel engine has incomplete combustion in the cylinder under low-temperature cold start conditions and the output power is small, the engine speed lasts for a long time in the resonance speed range of the dual-mass flywheel. This embodiment optimizes the starting strategy of the diesel engine so that the power source of the diesel DCT powertrain overcomes the resistance source of the diesel DCT powertrain, thereby enabling the starting speed of the diesel engine to quickly pass through the resonance range of the dual-mass flywheel to avoid the engine speed being maintained in the resonance speed range of the dual-mass flywheel when the engine is started. The resonance optimization method shown in this embodiment can effectively reduce the resonance generated by the power system in which the diesel engine and the DCT gearbox are matched with each other during low-temperature cold start, which is beneficial to improving the service life of the main components in the powertrain.

[0114] Embodiment 2

[0115] See also Fig. 9 , shown is a diesel DCT powertrain resonance optimization system provided by the second embodiment of the present invention, which is applied to the method described in the first embodiment above, and the system comprises:

[0116] The first processing module is used to obtain the starting speed and oil resistance of the diesel engine during cold start, and output a starting speed-oil resistance curve according to the starting speed and oil resistance;

[0117] The second processing module is used to obtain the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque;

[0118] In the third processing module, the user obtains the output power and output torque of the starter corresponding to different engine speeds, obtains the starter speed-output torque curve, and outputs the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel;

[0119] a fourth processing module, for obtaining cylinder pressure data of the diesel engine, outputting engine output torques corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine a maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve;

[0120] A curve fitting module is used to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve between the resistance source and the power source at different speeds of the diesel engine;

[0121] A simulation calculation module is used to calculate the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started through CAE simulation, and calculate the second-order resonant speed of the diesel DCT powertrain based on the first-order torsional vibration frequency;

[0122] The resonance optimization module is used to determine the resonance speed range of the second-order resonance speed in combination with the CAE simulation and according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonance speed range.

[0123] In this embodiment, the simulation calculation module is specifically used for:

[0124] The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during the diesel engine startup process is calculated through CAE simulation;

[0125] Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system;

[0126] The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

[0127] In this embodiment, the resonance optimization module is specifically used for:

[0128] Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined;

[0129] According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

[0130] Compared with the prior art, the diesel DCT powertrain resonance optimization system shown in this embodiment has the following beneficial effects:

[0131] This embodiment proposes for the first time a power system in which a diesel engine and a DCT gearbox are matched with each other. Since the diesel engine has incomplete combustion in the cylinder under low-temperature cold start conditions and the output power is small, the engine speed lasts for a long time in the resonance speed range of the dual-mass flywheel. This embodiment optimizes the starting strategy of the diesel engine so that the power source of the diesel DCT powertrain overcomes the resistance source of the diesel DCT powertrain, thereby enabling the starting speed of the diesel engine to quickly pass through the resonance range of the dual-mass flywheel to avoid the engine speed being maintained in the resonance speed range of the dual-mass flywheel when the engine is started. The resonance optimization system shown in this embodiment can effectively reduce the resonance generated by the power system in which the diesel engine and the DCT gearbox are matched with each other during low-temperature cold start, which is beneficial to improving the service life of the main components in the powertrain.

[0132] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0133] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A diesel DCT powertrain resonance optimization method, characterized in that: The method comprises: Obtain the starting speed and oil resistance of the diesel engine during cold start, and output a starting speed-oil resistance curve based on the starting speed and oil resistance; Obtain the drag torque of the gearbox in the parking gear when the diesel engine is cold started, and determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque; Obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel; Obtaining cylinder pressure data of the diesel engine, outputting engine output torque corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine the maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve; The maximum resistance source torque curve and the maximum power source torque curve are fitted to obtain the difference comparison curve between the resistance source and the power source at different speeds of the diesel engine; The first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started is calculated through CAE simulation, and the second-order resonant speed of the diesel DCT powertrain is calculated based on the first-order torsional vibration frequency; Combined with CAE simulation, the resonant speed range of the second-order resonant speed is determined according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonant speed range.

2. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that: The steps of combining CAE simulation and determining the resonance speed range of the second-order resonance speed according to the difference comparison curve, and optimizing the start strategy of the diesel DCT powertrain according to the resonance speed range, include: Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined; According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

3. The diesel DCT powertrain resonance optimization method according to claim 2, characterized in that: The calculation expression of the resonant frequency is: The calculation expression of the resonant speed is: n = 60f; Where f is the resonant frequency, K is the system stiffness, M is the system moment of inertia, and n is the resonant speed.

4. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that: The steps of obtaining the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determining the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque include: Connect the diesel engine to the DCT gearbox and arrange it on the bench equipment; Bench test of the DCT transmission to test the drag torque of the DCT transmission in the parking gear position during cold start of the diesel engine; According to the starting speed-oil resistance curve and the drag torque, the maximum resistance source torque curve of the diesel DCT powertrain is determined.

5. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that: The steps of obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel include: Monitor the starting voltage and starting current of the starter; According to the starting voltage and starting current of the starter, the output power and output torque of the starter corresponding to different engine speeds during cold start are obtained; According to the output power and output torque of the starter, the starter speed-output torque curve is output; Obtaining a transmission ratio between a drive ring gear in a starter and a signal ring gear in a dual mass flywheel; According to the transmission ratio between the driving ring gear in the starter and the signal ring gear in the dual mass flywheel, the ring gear output torque of the signal ring gear in the dual mass flywheel is output.

6. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that: The steps of calculating the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started by CAE simulation and calculating the second-order resonant speed of the diesel DCT powertrain according to the first-order torsional vibration frequency include: The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during diesel engine startup is calculated through CAE simulation; Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system; The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

7. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that: After optimizing the startup strategy of the diesel DCT powertrain, the method further includes: The speed information of the crankshaft position sensor is collected through the data acquisition terminal to identify the engine starting speed of the diesel engine; It is determined whether the engine starting speed exceeds the resonance speed range of the second-order resonance speed within a preset time.

8. A diesel DCT powertrain resonance optimization system, characterized in that: The method applied to any one of claims 1 to 7, wherein the system comprises: The first processing module is used to obtain the starting speed and oil resistance of the diesel engine during cold start, and output a starting speed-oil resistance curve according to the starting speed and oil resistance; The second processing module is used to obtain the drag torque of the gearbox in the parking gear position when the diesel engine is cold started, and determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque; In the third processing module, the user obtains the output power and output torque of the starter corresponding to different engine speeds, obtains the starter speed-output torque curve, and outputs the ring gear output torque of the signal ring gear in the dual mass flywheel according to the transmission ratio between the drive ring gear of the starter and the signal ring gear of the dual mass flywheel; a fourth processing module, for obtaining cylinder pressure data of the diesel engine, outputting engine output torques corresponding to different starting speeds according to the cylinder pressure data, determining the actual output torque of the diesel engine during cold start, and obtaining an engine speed-output torque curve, so as to determine a maximum power source torque curve of the diesel DCT powertrain according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve; A curve fitting module is used to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve between the resistance source and the power source at different speeds of the diesel engine; A simulation calculation module is used to calculate the first-order torsional vibration frequency of the torsional vibration system when the diesel engine is started through CAE simulation, and calculate the second-order resonant speed of the diesel DCT powertrain based on the first-order torsional vibration frequency; The resonance optimization module is used to determine the resonance speed range of the second-order resonance speed in combination with the CAE simulation according to the difference comparison curve, so as to optimize the starting strategy of the diesel DCT powertrain according to the resonance speed range.

9. The diesel DCT powertrain resonance optimization system according to claim 8, characterized in that: The simulation calculation module is specifically used for: The first-order torsional vibration frequency of the torsional vibration system composed of the engine crankshaft, dual-mass flywheel and DCT gearbox during diesel engine startup is calculated through CAE simulation; Calculate the second-order resonant speed of the entire diesel DCT powertrain system based on the first-order torsional vibration frequency of the torsional vibration system; The second-order resonant speed is characterized as the resonant speed of the dual-mass flywheel.

10. The diesel DCT powertrain resonance optimization system according to claim 8, characterized in that: The resonance optimization module is specifically used for: Combined with CAE simulation and based on the difference comparison curve, the resonance speed range of the second-order resonance speed is determined; According to the resonance speed range of the second-order resonance speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonance speed of the diesel DCT powertrain.

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