A diesel dct powertrain resonance optimization method and system

Abstract

The application discloses a diesel DCT power assembly resonance optimization method and system, and relates to the technical field of power assembly simulation testing. Since the combustion in the cylinder of a diesel engine is insufficient and the output power is small under a low-temperature cold starting condition, the engine speed is maintained in the resonance speed interval of a dual-mass flywheel for a long time. The starting strategy of the diesel engine is optimized, the power source of the diesel DCT power assembly overcomes the resistance source of the diesel DCT power assembly, and then the starting speed of the diesel engine can quickly pass through the resonance interval of the dual-mass flywheel, so that the engine speed of the engine during starting is not maintained in the resonance speed interval of the dual-mass flywheel. The resonance optimization method can effectively reduce the resonance generated by the power system matched with the diesel engine and the DCT gearbox during low-temperature cold starting, and is beneficial to prolonging the service life of main parts in the power assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powertrain simulation test, in particular to a diesel DCT powertrain resonance optimization method and system. BACKGROUND

[0002] In the field of automobiles, there are various powertrain combinations, such as front-engine front-drive gasoline engine matching manual transmission and various automatic transmissions (including AT\CVT\DCT), and front-engine front-drive diesel engine matching manual transmission and various automatic transmissions (including AT); However, front-engine front-drive diesel engine matching wet double clutch transmission (wet DCT) is rarely seen in the current Chinese market, so research on cold start related to powertrain matching diesel engine and double mass flywheel and wet double clutch transmission is relatively rare, and foreign automobile field is also less involved. In the vehicle model matching double mass flywheel (DMF), avoiding exciting DMF resonance when the engine starts has always been the focus of research in the field of automobiles, and for a powertrain combination of a diesel engine matching double mass flywheel and wet double clutch transmission, this problem is particularly prominent. There are also similar patents researching DMF resonance, which disclose resonance detection method of double mass flywheel and avoiding double mass flywheel resonance through engine software control.

[0003] However, diesel engines differ from gasoline engines in terms of combustion. Diesel engines mainly work through compression ignition. When the engine starts at low temperature, the combustion efficiency is low due to the low ambient temperature and cylinder temperature, the combustion in the engine cylinder is insufficient, resulting in less output torque of the engine during cold start; At the same time, the battery capacity decreases under low temperature, affecting the starting power (current and voltage during starting) of the starter, resulting in smaller output torque of the starter; At this time, the engine oil and transmission oil of the wet double clutch transmission have large drag torque under low temperature.

[0004] Therefore, in the prior art, under the condition of low temperature cold start, how to make the engine speed quickly pass through the DMF resonance speed range and avoid the engine speed being in the DMF resonance speed range for a long time to cause irreversible damage to each part of the whole transmission system has become an urgent problem in the industry. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims 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 pass through the DMF resonance speed range and reduce resonance, thereby solving the problems recorded in the prior art.

[0006] The first aspect of the present application provides 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 the 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 during the cold start of the diesel engine, 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] Obtain the output power and output torque of the starter corresponding to different engine speeds, obtain the starter speed-output torque curve, and output the gear output torque of the signal gear in the dual-mass flywheel according to the transmission ratio between the driving gear ring of the starter and the signal gear of the dual-mass flywheel;

[0010] Obtain the cylinder pressure data of the diesel engine, output the engine output torque corresponding to different starting speeds according to the cylinder pressure data, determine the actual output torque of the diesel engine during cold start, and obtain the 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 gear output torque and the engine speed-output torque curve;

[0011] Fit the maximum resistance source torque curve and the maximum power source torque curve to obtain the difference comparison curve of the resistance source and the power source under different speeds of the diesel engine;

[0012] Calculate the first-order torsional vibration frequency of the torsional vibration system of the diesel engine during startup through CAE simulation, and calculate the second-order resonance speed of the diesel DCT powertrain according to the first-order torsional vibration frequency;

[0013] Determine the resonance speed interval of the second-order resonance speed in combination with CAE simulation and according to the difference comparison curve, and optimize the startup strategy of the diesel DCT powertrain according to the resonance speed interval.

[0014] According to one aspect of the above technical solution, the step of determining the resonance speed interval of the second-order resonance speed in combination with CAE simulation and according to the difference comparison curve, and optimizing the startup strategy of the diesel DCT powertrain according to the resonance speed interval, comprises:

[0015] Determine the resonance speed interval of the second-order resonance speed in combination with CAE simulation and according to the difference comparison curve;

[0016] According to the resonance speed interval of the second-order resonance speed, increase the moment of inertia of the secondary flywheel in the dual-mass flywheel to reduce the resonance speed of the diesel DCT powertrain.

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

[0018]

[0019] The calculation expression of the resonance rotational speed is:

[0020] n = 60f

[0021] In the formula, f is the resonance frequency, K is the system stiffness, M is the system rotational inertia, and n is the resonance rotational speed.

[0022] According to an aspect of the above technical solution, the step of obtaining the drag torque of the gearbox in the parking gear when the diesel engine is cold-starting, 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, comprises:

[0023] The diesel engine is connected with the DCT gearbox and arranged on a bench device;

[0024] The DCT gearbox is subjected to bench testing, and the drag torque of the DCT gearbox in the parking gear when the diesel engine is cold-starting is tested;

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

[0026] According to an aspect of the above technical solution, the output power and the output torque of the starter corresponding to different engine rotational speeds are obtained, the starter speed-output torque curve is obtained, and the step of outputting the gear output torque of the signal gear in the dual-mass flywheel according to the transmission ratio between the driving gear in the starter and the signal gear in the dual-mass flywheel, comprises:

[0027] The starting voltage and the starting current of the starter are monitored;

[0028] The output power and the output torque of the starter corresponding to different engine rotational speeds when cold-starting are obtained according to the starting voltage and the starting current of the starter;

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

[0030] The transmission ratio between the driving gear in the starter and the signal gear in the dual-mass flywheel is obtained;

[0031] The gear output torque of the signal gear in the dual-mass flywheel is output according to the transmission ratio between the driving gear in the starter and the signal gear in the dual-mass flywheel.

[0032] According to one aspect of the above technical solution, the first-order torsional vibration frequency of the torsional vibration system during the starting of the diesel engine is calculated through CAE simulation, and the second-order resonance speed of the diesel DCT power assembly is calculated according to the first-order torsional vibration frequency, including:

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

[0034] The second-order resonance speed of the entire diesel DCT power assembly system is calculated according to the first-order torsional vibration frequency of the torsional vibration system.

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

[0036] According to one aspect of the above technical solution, after the starting strategy of the diesel DCT power assembly is optimized, the method further includes:

[0037] 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.

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

[0039] The second aspect of the present application provides a diesel DCT power assembly resonance optimization system, which is applied to the method in the above technical solution, and the system includes:

[0040] The first processing module is used for obtaining the starting speed and oil resistance of the diesel engine during cold starting, and outputting the starting speed-oil resistance curve according to the starting speed and oil resistance.

[0041] The second processing module is used for obtaining the drag torque of the gearbox in the parking gear during the cold starting of the diesel engine, and determining the maximum resistance source torque curve of the diesel DCT power assembly according to the starting speed-oil resistance curve and the drag torque.

[0042] The third processing module is used for obtaining the output power and output torque of the starter corresponding to different engine speeds, obtaining the starter speed-output torque curve, and outputting the gear output torque of the signal gear in the dual-mass flywheel according to the transmission ratio between the driving gear ring of the starter and the signal gear of the dual-mass flywheel.

[0043] The fourth processing module is configured to acquire cylinder pressure data of the diesel engine, output engine output torque corresponding to different starting rotation speeds according to the cylinder pressure data, determine actual output torque of the diesel engine at the cold start, and obtain an engine rotation speed-output torque curve, so as to determine a maximum power source torque curve of the diesel DCT power system according to the starter rotation speed-output torque curve, the ring gear output torque and the engine rotation speed-output torque curve.

[0044] The curve fitting module is configured to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve of the resistance source and the power source at different rotation speeds of the diesel engine.

[0045] The simulation calculation module is configured to calculate a first-order torsional vibration frequency of a torsional vibration system of the diesel engine at the start by CAE simulation, and calculate a second-order resonance rotation speed of the diesel DCT power system according to the first-order torsional vibration frequency.

[0046] The resonance optimization module is configured to determine a resonance rotation speed interval of the second-order resonance rotation speed in combination with the CAE simulation and according to the difference comparison curve, and optimize a starting strategy of the diesel DCT power system according to the resonance rotation speed interval.

[0047] According to an aspect of the above technical solution, the simulation calculation module is specifically configured to:

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

[0049] The second-order resonance rotation speed of the entire diesel DCT power system is calculated according to the first-order torsional vibration frequency of the torsional vibration system.

[0050] The second-order resonance rotation speed is represented as the resonance rotation speed of the dual-mass flywheel.

[0051] According to an aspect of the above technical solution, the resonance optimization module is specifically configured to:

[0052] The resonance rotation speed interval of the second-order resonance rotation speed is determined in combination with the CAE simulation and according to the difference comparison curve.

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

[0054] Compared with the prior art, the diesel DCT power system resonance optimization method and system shown in the present application has the beneficial effects that:

[0055] The application first proposes a power system matched with a diesel engine and a DCT gearbox, and because the combustion in the cylinder of the diesel engine is insufficient and the output power is small in the low-temperature cold starting condition, the engine speed is maintained in the resonance speed interval of the dual-mass flywheel for a long time, the application optimizes the starting strategy of the diesel engine, 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 speed of the diesel engine can quickly pass through the resonance interval of the dual-mass flywheel, so as to avoid the engine speed being maintained in the resonance speed interval of the dual-mass flywheel during engine starting, and the resonance generated by the power system matched with the diesel engine and the DCT gearbox in the low-temperature cold starting condition can be effectively reduced by using the resonance optimization method, which is beneficial to improving the service life of the main parts in the power assembly. BRIEF DESCRIPTION OF DRAWINGS

[0056] The above and / or additional aspects and advantages of the application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings in which:

[0057] Figure 1 It is a flowchart of the diesel DCT power assembly resonance optimization method in an embodiment of the application;

[0058] Figure 2 It is a structural diagram of the diesel DCT power assembly in an embodiment of the application;

[0059] Figure 3 It is a diesel engine speed-oil resistance curve diagram during low-temperature cold starting in an embodiment of the application;

[0060] Figure 4 It is a starter speed-output torque curve diagram during low-temperature cold starting in an embodiment of the application;

[0061] Figure 5 It is a diesel engine speed-output torque curve diagram during low-temperature cold starting of the engine in an embodiment of the application;

[0062] Figure 6 It is a comparison curve diagram of driving force and resistance during engine starting in an embodiment of the application;

[0063] Figure 7 It is a CAE calculation result diagram of the first-order torsional vibration frequency of the power assembly system in the prior art DMF scheme;

[0064] Figure 8 It is a CAE calculation result diagram of the first-order torsional vibration frequency of the power assembly system in the new DMF scheme in an embodiment of the application;

[0065] Figure 9A structural block diagram of a diesel DCT power assembly resonance optimization system in an embodiment of the present application. DETAILED DESCRIPTION

[0066] In order to make the objects, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. The accompanying drawings show several embodiments of the present application. However, the present application can be realized 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 application more thorough and comprehensive.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0068] Embodiment One

[0069] Figure 1 A flowchart of a diesel DCT power assembly resonance optimization method provided by the first embodiment of the present application is shown in FIG. 1. The hardware structure of the diesel DCT power assembly is shown in FIG. 2, which 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 flywheel disc of the dual-mass flywheel 2 is first driven to rotate by the starter 4, thereby driving the crankshaft of the diesel engine 1 to rotate, and through software control, fuel is injected into the cylinder to realize in-cylinder compression ignition, and then the dual-mass flywheel 2 and the wet dual clutch transmission 3 at the rear end are driven to move. Figure 2

[0070] The method includes steps S10-S70:

[0071] In step S10, the starting speed and oil resistance of the diesel engine during cold start are obtained, and a starting speed-oil resistance curve is output according to the starting speed and the oil resistance.

[0072] In this embodiment, as shown in FIG. 3, the starting speed-oil resistance curve of the diesel engine during low-temperature cold start is obtained through engine bench testing, and the maximum torque that the diesel engine can output at different speeds during the low-temperature cold start process of the diesel engine is obtained, and the resistance of the diesel engine at low oil temperature is obtained. Figure 3

[0073] ​​Step S20, 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.

[0074] The step of obtaining the drag torque of the gearbox in the parking gear 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, comprises:

[0075] Connect the diesel engine with the DCT gearbox and arrange it on a bench device;

[0076] Perform bench test on the DCT gearbox, and test the drag torque of the DCT gearbox in the parking gear when the diesel engine is cold started;

[0077] Determine the maximum resistance source torque curve of the diesel DCT powertrain according to the starting speed-oil resistance curve and the drag torque.

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

[0079] Step S30, obtain the output power and output torque of the starter corresponding to different engine speeds, obtain the starter speed-output torque curve, and output the gear output torque of the signal gear in the dual-mass flywheel according to the transmission ratio between the driving gear of the starter and the signal gear of the dual-mass flywheel.

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

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

[0082] According to the starting voltage and starting current of the starter, obtain the output power and output torque of the starter corresponding to different engine speeds when cold started;

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

[0084] Obtain the transmission ratio between the driving gear in the starter and the signal gear in the dual-mass flywheel.

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

[0086] It should be noted that the dual mass flywheel, i.e. DMF, is a full name of Dual Mass Flywheel, and its existence can greatly improve the torsional vibration problem of the engine.

[0087] Specifically, the dual mass flywheel has many different structural forms, and generally consists 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 to drive the first mass to rotate. At this time, the circumferential spring is connected to the clamping groove on the first mass, and the circumferential spring is compressed to transmit power to the transmission plate. The transmission plate is rigidly connected to the second mass, and then the power is transmitted to the input end of the transmission, completing the transmission of power. In essence, through the structural design of the dual mass flywheel, the original flywheel is cut into two parts, and the power is transmitted through the spiral spring in the middle, thereby forming a torsional vibration system and realizing the function of vibration isolation.

[0088] In this embodiment, as shown in Figure 4 , the output power of the starter at different engine speeds under low temperature condition of the starter is tested by monitoring the starting voltage and starting current of the starter, and then the output torque of the starter is obtained, that is, the starter speed-output torque curve under low temperature cold start is obtained. Then, according to the transmission ratio between the driving 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 driving ring gear of the starter and the signal ring gear of the dual mass flywheel is 1:10, that is, the output torque of the starter is amplified by 10 times, and then the output torque on the signal ring gear of the dual mass flywheel is obtained.

[0089] In step S40, the cylinder pressure data of the diesel engine is obtained, the engine output torque corresponding to different starting speeds is output according to the cylinder pressure data, the actual output torque of the diesel engine under cold start is determined, the engine speed-output torque curve is obtained, and the maximum power source torque curve of the diesel DCT powertrain is determined according to the starter speed-output torque curve, the ring gear output torque and the engine speed-output torque curve.

[0090] In this embodiment, as shown in Figure 5 , the engine output torque at different starting speeds is obtained by testing the cylinder pressure data on the engine test bench, the actual output torque of the diesel engine under low temperature working condition can be displayed, and the diesel engine speed-output torque curve as shown in Figure 4 is obtained.

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

[0092] In this embodiment, as shown in Figure 6 According to the test data, the difference comparison curve of the resistance source and the power source at different engine speeds can be preliminarily fitted by considering the damping effect of the DMF at low temperature, and it can be seen that the driving torque (power source) and the resistance torque (resistance source) are close in a certain speed range. If the resonance speed range of the entire powertrain coincides with the range, resonance of the dual-mass flywheel, i.e. resonance of the entire transmission system, is easy to occur. Therefore, the resonance generated when the cold-start diesel engine starts needs to be optimized in this embodiment, for example, the calibration of the starting speed is optimized.

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

[0094] The step of calculating the first-order torsional vibration frequency of the torsional vibration system of the diesel engine during starting by CAE simulation and calculating the second-order resonance speed of the diesel DCT powertrain according to the first-order torsional vibration frequency includes:

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

[0096] The second-order resonance speed of the entire diesel DCT powertrain system is calculated according to the first-order torsional vibration frequency of the torsional vibration system.

[0097] The second-order resonance speed is represented as the resonance 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, the DMF and the DCT gearbox in the starting state of the engine is calculated by CAE simulation, and the second-order resonance speed of the entire diesel DCT powertrain is calculated. The second-order resonance speed can be represented as the DMF resonance speed. It can be seen that the resonance frequency of the entire powertrain of the original DMF scheme in this embodiment is 12.2 HZ, which is converted into the second-order resonance speed of the engine as 366 rpm, as shown by n1 in Figure 7

[0099] Step S70, determining the resonance speed range of the second-order resonance speed in combination with 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.

[0100] ​The resonance speed interval of the second-order resonance speed is determined in combination with CAE simulation and according to the difference comparison curve, and a step of optimizing the starting strategy of the diesel DCT power assembly according to the resonance speed interval comprises the following steps:

[0101] The resonance speed interval of the second-order resonance speed is determined in combination with CAE simulation and according to the difference comparison curve;

[0102] According to the resonance speed interval of the second-order resonance speed, the rotational inertia of the secondary flywheel in the double-mass flywheel is increased to reduce the resonance speed of the diesel DCT power assembly.

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

[0104]

[0105] The calculation expression of the resonance speed is as follows:

[0106] n = 60f;

[0107] In the formula, f is the resonance frequency, K is the system stiffness, M is the system rotational inertia, and n is the resonance speed.

[0108] After the starting strategy of the diesel DCT power assembly is optimized, the method further comprises the following steps:

[0109] 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;

[0110] It is judged whether the engine starting speed is in the resonance speed interval of the second-order resonance speed within a preset time.

[0111] In this embodiment, according to the theoretical calculation formula of the resonance frequency and the resonance speed, increasing the rotational inertia of the DMF secondary flywheel is beneficial to the resonance speed of the entire power assembly. After the resonance speed is reduced, the output torque of the starter is greater, and the power source will be greater than the resistance source, which is beneficial to the engine starting to quickly pass through the DMF resonance interval and avoid exciting the 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 power assembly can be reduced to 9HZ, which is converted into the second-order resonance speed of the engine as 270rpm, as indicated by n2 in Figure 8 In this embodiment, by optimizing the starting strategy, the diesel DCT power assembly can quickly pass through the resonance speed during low-temperature starting, and avoid maintaining in the resonance speed interval to cause serious damage to the parts.

[0112] Compared with the prior art, the diesel DCT powertrain resonance optimization method has the beneficial effects that:

[0113] The diesel engine and the DCT gearbox are matched with each other in the power system, and the diesel engine has insufficient combustion in the cylinder and small output power in the low-temperature cold starting condition, so that the engine speed is maintained in the resonance speed interval of the dual-mass flywheel for a long time. The starting strategy of the diesel engine is optimized, the power source of the diesel DCT powertrain overcomes the resistance source of the diesel DCT powertrain, and then the starting speed of the diesel engine can quickly pass through the resonance interval of the dual-mass flywheel, so as to avoid the engine speed being maintained in the resonance speed interval of the dual-mass flywheel during the engine starting. The resonance optimization method can effectively reduce the resonance of the diesel engine and the DCT gearbox in the low-temperature cold starting condition, and is beneficial to prolonging the service life of the main parts in the powertrain.

[0114] Embodiment two

[0115] Please refer to Figure 9 , which is a diesel DCT powertrain resonance optimization system provided by the second embodiment of the present application, applied to the method in the first embodiment, the system comprises:

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

[0117] The second processing module is used for obtaining the drag torque of the gearbox in the parking gear during the cold starting of the diesel engine, 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;

[0118] The third processing module is used for obtaining the output power and the output torque of the starter corresponding to different engine speeds, obtaining a starter speed-output torque curve, and outputting the gear output torque of the signal gear in the dual-mass flywheel according to the transmission ratio between the driving gear ring of the starter and the signal gear of the dual-mass flywheel;

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

[0120] The curve fitting module is configured to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a difference comparison curve of the resistance source and the power source of the diesel engine at different rotational speeds.

[0121] The simulation calculation module is configured to calculate a first torsional vibration frequency of a torsional vibration system of the diesel engine during startup by CAE simulation, and calculate a second resonance rotational speed of the diesel DCT powertrain according to the first torsional vibration frequency.

[0122] The resonance optimization module is configured to determine a resonance rotational speed interval of the second resonance rotational speed in combination with the CAE simulation and according to the difference comparison curve, and optimize a startup strategy of the diesel DCT powertrain according to the resonance rotational speed interval.

[0123] In the embodiment, the simulation calculation module is specifically configured to:

[0124] calculate a first torsional vibration frequency of a torsional vibration system composed of the engine crankshaft, the dual-mass flywheel and the DCT gearbox during startup of the diesel engine by CAE simulation;

[0125] calculate a second resonance rotational speed of the entire diesel DCT powertrain system according to the first torsional vibration frequency of the torsional vibration system;

[0126] The second resonance rotational speed is represented as a resonance rotational speed of the dual-mass flywheel.

[0127] In the embodiment, the resonance optimization module is specifically configured to:

[0128] determine a resonance rotational speed interval of the second resonance rotational speed in combination with the CAE simulation and according to the difference comparison curve;

[0129] increase a rotational inertia of a secondary flywheel in the dual-mass flywheel to reduce the resonance rotational speed of the diesel DCT powertrain according to the resonance rotational speed interval of the second resonance rotational speed.

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

[0131] The embodiment first proposes a power system matched with a diesel engine and a DCT gearbox, and because the combustion in the cylinder of the diesel engine is insufficient and the output power is small in the low-temperature cold start condition, the engine speed is maintained in the resonance speed interval of the dual-mass flywheel for a long time. The embodiment optimizes the starting strategy of the diesel engine, 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 speed of the diesel engine can quickly pass through the resonance interval of the dual-mass flywheel, so as to avoid the engine speed being maintained in the resonance speed interval of the dual-mass flywheel when the engine starts. Therefore, the resonance optimization system shown in the embodiment can effectively reduce the resonance generated by the power system matched with the diesel engine and the DCT gearbox in the low-temperature cold start, and is beneficial to prolong the service life of the main parts in the power assembly.

[0132] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0133] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that, for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for optimizing resonance in a diesel DCT powertrain, characterized in that, The method includes: Obtain the starting speed and oil resistance of a diesel engine during cold start, and output the starting speed-oil resistance curve based on the starting speed and oil resistance. The drag torque of the transmission in parking gear when the diesel engine is cold started is obtained, and the maximum resistance source torque curve of the diesel DCT powertrain is determined based on the starting speed-oil resistance curve and the drag torque. The output power and output torque of the starter corresponding to different engine speeds are obtained to obtain the starter speed-output torque curve. Based on the transmission ratio between the drive gear ring of the starter and the signal gear ring of the dual-mass flywheel, the output torque of the signal gear ring in the dual-mass flywheel is output. Obtain the cylinder pressure data of the diesel engine, output the engine output torque corresponding to different starting speeds based on the cylinder pressure data, determine the actual output torque of the diesel engine during cold start, and obtain the engine speed-output torque curve. Based on the starter speed-output torque curve, the gear ring output torque and the engine speed-output torque curve, determine the maximum power source torque curve of the diesel DCT powertrain. By fitting the torque curve of the maximum resistance source and the torque curve of the maximum power source, a comparison curve of the difference between the resistance source and the power source at different speeds of the diesel engine is obtained. The first-order torsional vibration frequency of the diesel engine's torsional vibration system during startup is calculated using CAE simulation, and the second-order resonance speed of the diesel DCT powertrain is calculated based on the first-order torsional vibration frequency. By combining CAE simulation and determining the resonance speed range of the second-order resonance speed based on the difference comparison curve, the starting strategy of the diesel DCT powertrain can be optimized according to the resonance speed range.

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

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

4. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that, The steps for obtaining the drag torque of the transmission in parking gear during a cold start of a diesel engine, and determining the maximum resistance source torque curve of the diesel DCT powertrain based on the starting speed-oil resistance curve and the drag torque, include: The diesel engine and DCT transmission are connected and mounted on a test bench. A bench test was conducted on the DCT transmission to test the drag torque of the DCT transmission in parking gear during a cold start of the diesel engine. Based on the starting speed-oil resistance curve and 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 starter's output power and output torque corresponding to different engine speeds, obtaining the starter speed-output torque curve, and outputting the output torque of the signal gear ring in the dual-mass flywheel based on the transmission ratio between the starter's drive gear ring and the signal gear ring of the dual-mass flywheel include: Monitor the starting voltage and starting current of the starter motor; Based on the starter's starting voltage and starting current, obtain the starter's output power and output torque corresponding to different engine speeds during cold start; Based on the starter motor's output power and output torque, output the starter motor speed-output torque curve; Obtain the transmission ratio between the drive gear ring in the starter and the signal gear ring in the dual-mass flywheel; Based on the transmission ratio between the drive gear ring in the starter and the signal gear ring in the dual-mass flywheel, the output torque of the signal gear ring in the dual-mass flywheel is determined.

6. The diesel DCT powertrain resonance optimization method according to claim 1, characterized in that, The steps for calculating the first-order torsional vibration frequency of the diesel engine's torsional vibration system during startup using CAE simulation, and then calculating the second-order resonance speed of the diesel DCT powertrain based on the first-order torsional vibration frequency, include: The first-order torsional vibration frequency of the torsional vibration system consisting of the engine crankshaft, dual-mass flywheel and DCT transmission during the diesel engine start-up process was calculated using CAE simulation. The second-order resonant speed of the entire diesel DCT powertrain system is calculated 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 starting strategy of the diesel DCT powertrain, the method further includes: The crankshaft position sensor's rotational speed information is collected through a data acquisition terminal to identify the diesel engine's starting speed. Determine 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 system, applicable to the method of any one of claims 1-7, comprises: The first processing module is used to obtain the starting speed and oil resistance of the diesel engine during cold start, and output the starting speed-oil resistance curve based on the starting speed and oil resistance. The second processing module is used to obtain the drag torque of the transmission in parking gear when the diesel engine is cold started, and to determine the maximum resistance source torque curve of the diesel DCT powertrain based on the starting speed-oil resistance curve and the drag torque. The third processing module allows the user to obtain the starter's output power and output torque corresponding to different engine speeds, obtain the starter speed-output torque curve, and output the output torque of the signal gear ring in the dual-mass flywheel based on the transmission ratio between the starter's drive gear ring and the signal gear ring of the dual-mass flywheel. The fourth processing module is used to acquire the cylinder pressure data of the diesel engine, output the engine output torque corresponding to different starting speeds based on the cylinder pressure data, determine the actual output torque of the diesel engine during cold start, and obtain the engine speed-output torque curve. Based on the starter speed-output torque curve, the gear ring output torque and the engine speed-output torque curve, the maximum power source torque curve of the diesel DCT powertrain is determined. The curve fitting module is used to fit the maximum resistance source torque curve and the maximum power source torque curve to obtain a comparison curve of the difference between the resistance source and the power source at different engine speeds. The simulation calculation module is used to calculate the first-order torsional vibration frequency of the diesel engine's torsional vibration system during startup using CAE simulation, and to calculate the second-order resonance speed of the diesel DCT powertrain based on the first-order torsional vibration frequency. The resonance optimization module is used to combine CAE simulation and determine the resonance speed range of the second-order resonance speed based on 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 consisting of the engine crankshaft, dual-mass flywheel and DCT transmission during the diesel engine start-up process was calculated using CAE simulation. The second-order resonant speed of the entire diesel DCT powertrain system is calculated 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: The resonant speed range of the second-order resonant speed is determined by combining CAE simulation and based on the difference comparison curve; Based on the resonant speed range of the second-order resonant speed, the rotational inertia of the secondary flywheel in the dual-mass flywheel is increased to reduce the resonant speed of the diesel DCT powertrain.

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