An engine start control method for a parallel P2 hybrid configuration

Abstract

The application relates to an engine starting control method for a parallel P2 hybrid configuration, which comprises the following steps: firstly, obtaining an engine ignition target rotating speed, a clutch sliding friction pressure and a motor target driving torque according to driving working condition information; secondly, controlling the clutch sliding friction with the engine sliding friction pressure to drag the engine to the engine ignition target rotating speed; thirdly, judging whether the lock-up clutch is unlocked according to the driving working condition information, controlling the clutch to be disconnected with the engine in the case of the lock-up clutch being closed; and finally, starting the engine and adjusting the rotating speed of the engine until the rotating speed of the engine reaches a preset condition, and completely connecting the clutch and the engine. Compared with the prior art, the engine starting impact is not transmitted to the transmission system through the clutch in the starting process when the lock-up clutch is closed, the impact on the transmission system in the engine starting process can be obviously reduced, and the driving smoothness is improved.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle control technology, and in particular to an engine start-up control method for a parallel P2 hybrid configuration. Background Technology

[0002] The parallel P2 hybrid configuration, as a type of parallel hybrid, has only one electric motor, which is positioned between the engine and the transmission, or can be integrated with the transmission, effectively saving space. (See attached image.) Figure 1 As shown, the system comprises an engine, a clutch (C0 clutch in the diagram), an electric motor (P2 motor in the diagram), and an automatic transmission (AT gearbox). The AT gearbox includes a lock-up clutch and a planetary gear mechanism. The lock-up clutch includes a pump wheel, a turbine, and a guide wheel, etc. Its characteristic is that it transmits power by means of the high-speed movement of the liquid, and has automatic adaptability, vibration reduction and isolation performance, etc. The electric motor can drive the vehicle alone, in which case the clutch is disengaged; it can also drive the vehicle together with the engine, in which case the clutch is engaged; it can also generate electricity by driving the motor through the engine, or use the vehicle's kinetic energy for braking energy recovery and coasting energy recovery, with the electricity stored in a high-voltage battery.

[0003] The parallel P2 hybrid drive structure is similar to the traditional fuel drive structure, with only the addition of a clutch and a motor between the engine and the automatic transmission. The modifications are minor, and it can achieve multiple working modes such as pure oil drive, pure electric drive, hybrid drive, engine power generation, and energy recovery.

[0004] However, in existing P2 hybrid systems, starting the engine while the vehicle is in motion requires disengaging the lock-up clutch; otherwise, a strong impact occurs, affecting driving smoothness. Conversely, unlocking the lock-up clutch causes sluggish vehicle response, impacting drivability. Therefore, there is an urgent need for a method that can start the engine with minimal impact while the lock-up clutch is engaged. Summary of the Invention

[0005] In view of this, it is necessary to provide an engine start control method for a parallel P2 hybrid configuration to solve the problem of large engine start-up impact force in the prior art when the lock-up clutch is engaged.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] This invention provides an engine start-up control method for a parallel P2 hybrid configuration, comprising:

[0008] Obtain vehicle operating condition information;

[0009] Based on the driving condition information, the target engine ignition speed, clutch slip pressure, and target motor drive torque are obtained.

[0010] The clutch slippage pressure is controlled to control the slippage between the clutch and the engine, and the engine is towed up to the engine ignition target speed based on the target drive torque of the motor;

[0011] Based on the driving condition information, determine whether the lock-up clutch is unlocked. If so, maintain the slipping state between the clutch and the engine. If not, control the clutch to disconnect from the engine.

[0012] Start the engine and adjust its speed until it reaches a preset speed, then fully engage the clutch and the engine.

[0013] Furthermore, the driving condition information includes the required driving torque, the lock-up clutch status (indicating whether the lock-up clutch is unlocked), engine coolant temperature, first vehicle condition information, and second vehicle condition information; obtaining the engine ignition target speed, clutch slip pressure, and electric motor target drive torque based on the driving condition information includes:

[0014] Based on the state of the lock-up clutch, the target engine ignition speed is obtained by combining the first vehicle condition information and the second vehicle condition information.

[0015] Based on the engine coolant temperature and the engine ignition target speed, the required engine starting torque is obtained;

[0016] The clutch slip pressure is obtained based on the engine starting torque requirement;

[0017] Based on the state of the lock-up clutch, the engine starting torque is corrected by combining the first vehicle condition information and the second vehicle condition information, and the target drive torque of the motor is obtained based on the driving torque.

[0018] Furthermore, the first vehicle condition information includes acceleration / deceleration conditions used to characterize whether the vehicle is accelerating, decelerating, or moving at a constant speed; the step of obtaining the engine ignition target speed based on the lock-up clutch state, combined with the first and second vehicle condition information, includes:

[0019] When the lock-up clutch is unlocked, a preset speed value is obtained as the engine ignition required speed, and the engine ignition required speed is corrected according to the engine coolant temperature to obtain the engine ignition target speed.

[0020] When the lock-up clutch is locked, the current actual speed of the motor is obtained as the engine ignition required speed, and the engine ignition required speed is corrected according to the acceleration and deceleration conditions and the second vehicle condition information to obtain the engine ignition target speed.

[0021] Furthermore, the second vehicle condition information includes pedal opening, gear ratio, and vehicle speed, wherein the pedal opening includes accelerator pedal opening and brake pedal opening; the step of correcting the engine ignition demand speed based on the acceleration / deceleration conditions and the second vehicle condition information to obtain the engine ignition target speed includes:

[0022] If the vehicle is accelerating, the engine ignition speed requirement is adjusted according to the accelerator pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed.

[0023] If the vehicle is decelerating, the engine ignition speed requirement is adjusted according to the brake pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed.

[0024] If the vehicle is moving at a constant speed, then the engine ignition required speed is taken as the engine ignition target speed.

[0025] Furthermore, the step of correcting the engine starting torque requirement based on the lock-up clutch state, combined with the first vehicle condition information and the second vehicle condition information, and obtaining the target drive torque of the electric motor based on the driving torque requirement, includes:

[0026] Based on the state of the lock-up clutch, a first correction coefficient is obtained;

[0027] Based on the acceleration / deceleration conditions, a second correction coefficient is obtained based on the rate of change of the pedal opening;

[0028] The engine starting torque is corrected based on the first correction coefficient and the second correction coefficient, and the target driving torque of the motor is obtained based on the driving torque.

[0029] Furthermore, obtaining the first correction coefficient based on the lock-up clutch state includes:

[0030] When the lock-up clutch is unlocked, the first correction coefficient is obtained based on the torque transmission characteristics of the lock-up clutch.

[0031] Furthermore, the step of obtaining the second correction coefficient based on the pedal opening according to the acceleration / deceleration condition includes:

[0032] If the vehicle is accelerating, the second correction coefficient is obtained based on the rate of change of the accelerator pedal opening.

[0033] If the vehicle is decelerating, the second correction coefficient is obtained based on the rate of change of the brake pedal opening.

[0034] Furthermore, the step of controlling the slippage between the clutch and the engine based on the clutch slippage pressure, and towing the engine to the engine ignition target speed based on the target drive torque of the motor, includes:

[0035] Real-time acquisition of motor torque;

[0036] If the vehicle is in an acceleration state or a constant speed state, when the real-time torque of the motor is increased to the required torque of the motor, the clutch and the engine are controlled to start slipping according to the clutch slipping pressure.

[0037] If the vehicle is decelerating, the clutch and engine are directly controlled to slip based on the clutch slip pressure.

[0038] Furthermore, the control of disconnecting the clutch from the engine includes:

[0039] The clutch is gradually disconnected from the engine, while the torque of the motor is simultaneously controlled to change from the target drive torque to the required driving torque.

[0040] Furthermore, the preset conditions include:

[0041] When the lock-up clutch is unlocked, the difference between the engine speed and the motor speed is less than the first speed difference;

[0042] When the lock-up clutch is unlocked, the difference between the engine speed and the motor speed is less than the second speed difference;

[0043] Wherein, the second speed difference is smaller than the first speed difference.

[0044] This invention provides an engine start-up control method for a parallel P2 hybrid configuration. First, it acquires vehicle operating condition information and, based on this information, obtains the engine ignition target speed, clutch slip pressure, and motor target drive torque. Then, it controls the clutch to slip with the engine based on the clutch slip pressure and, based on the motor target drive torque, tows the engine to the engine ignition target speed. Next, it determines whether the lock-up clutch is unlocked based on the vehicle operating condition information. If unlocked, the slip state between the clutch and the engine is maintained; otherwise, the clutch is disconnected from the engine. Finally, the engine is started and its speed is adjusted until it reaches a preset speed, fully engaging the clutch and the engine. Compared to existing technologies, this invention utilizes the hydraulic transmission characteristics of the lock-up clutch during unlocking to reduce the impact on the transmission system during engine start-up. Conversely, when the lock-up clutch is engaged, it disengages during start-up, preventing the engine start-up impact from being transmitted to the transmission system through the clutch. This significantly reduces the impact on the transmission system during engine start-up and improves driving smoothness. Attached Figure Description

[0045] Figure 1 This is a structural schematic diagram of a parallel P2 hybrid configuration in the prior art;

[0046] Figure 2 A flowchart illustrating an embodiment of the engine start-up control method for a parallel P2 hybrid configuration provided by the present invention.

[0047] Figure 3 for Figure 2 A flowchart of a method according to an embodiment of step S202;

[0048] Figure 4 for Figure 3 A flowchart of a method according to an embodiment of step S301;

[0049] Figure 5 for Figure 3 A flowchart of a method according to an embodiment of step S304. Detailed Implementation

[0050] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0051] It is understood that the technical terms and English abbreviations used in this article are all existing technologies, and those skilled in the art can understand their meaning based on the context. Due to space limitations, they will not be explained in detail here.

[0052] In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically defined.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] Combination Figure 2 As shown, a specific embodiment of the present invention discloses an engine start-up control method for a parallel P2 hybrid configuration, comprising:

[0055] S201. Obtain vehicle operating condition information;

[0056] S202. Based on the driving condition information, obtain the engine ignition target speed, clutch slip pressure and motor target drive torque;

[0057] S203. Control the slippage between the clutch and the engine according to the clutch slippage pressure, and lift the engine to the engine ignition target speed based on the target drive torque of the motor;

[0058] S204. Determine whether the lock-up clutch is unlocked based on the driving condition information. If yes, maintain the slipping state between the clutch and the engine. If no, control the clutch to disconnect from the engine.

[0059] S205. Start the engine and adjust the engine speed until the engine speed reaches the preset condition, and fully engage the clutch and the engine.

[0060] Compared to existing technologies, this invention utilizes the hydraulic transmission characteristics of the lock-up clutch during unlocking to reduce the impact on the transmission system during engine startup. Conversely, when the lock-up clutch is engaged, the clutch is disengaged during startup, preventing the engine startup impact from being transmitted to the transmission system through the clutch. This significantly reduces the impact on the transmission system during engine startup and improves driving smoothness.

[0061] It should be noted that, in the above process, driving condition information refers to data related to the vehicle's driving status and operating conditions, including vehicle speed, SOC, pedal opening, and temperature. This information can be acquired and recorded through devices such as onboard sensors, dashcams, and vehicle diagnostic tools.

[0062] The engine ignition target speed refers to the speed at which the engine is expected to ignite in practice in order to reduce impact, which is different from the speed required by the engine in theory.

[0063] Similarly, the target drive torque of the motor refers to the torque that the motor needs to output when towing the engine in actual operation in order to reduce impact, which is different from the torque that the motor needs to output when towing the engine in theoretical condition.

[0064] Specifically, in combination Figure 3 As shown, in a preferred embodiment, the driving condition information includes driving demand torque, lock-up clutch status (indicating whether the lock-up clutch is unlocked), engine coolant temperature, first vehicle condition information, and second vehicle condition information; step S202, obtaining the engine ignition target speed, clutch slip pressure, and motor target drive torque based on the driving condition information, specifically includes:

[0065] S301. Based on the state of the lock-up clutch, and in combination with the first vehicle condition information and the second vehicle condition information, the engine ignition target speed is obtained.

[0066] S302. Based on the engine coolant temperature and the engine ignition target speed, obtain the engine starting torque requirement;

[0067] S303. Obtain the clutch slip pressure based on the engine starting torque requirement;

[0068] S304. Based on the state of the lock-up clutch, the engine starting torque is corrected by combining the first vehicle condition information and the second vehicle condition information, and the target drive torque of the motor is obtained based on the driving torque.

[0069] In the above process, the driving torque requirement is the torque that the motor needs to output in order for the vehicle to achieve the desired driving conditions, and the engine start torque requirement is the torque that the motor needs to output when the engine is started alone. The sum of the driving torque requirement and the engine start torque requirement is the target driving torque of the motor.

[0070] Since the engine starting torque required in this embodiment is calculated with reference to the engine coolant temperature, the target driving torque of the motor obtained in this embodiment is closer to the actual situation than the torque that the motor needs to output when towing the engine under purely theoretical conditions, which can improve starting efficiency.

[0071] Furthermore, in combination Figure 4As shown, in a preferred embodiment, the first vehicle condition information includes acceleration / deceleration conditions characterizing whether the vehicle is accelerating, decelerating, or moving at a constant speed; step S301 in the above process, obtaining the engine ignition target speed based on the lock-up clutch state, combined with the first and second vehicle condition information, includes:

[0072] S401. Determine whether the locking clutch is unlocked;

[0073] When the locking clutch is unlocked:

[0074] S402. Obtain the preset speed value as the engine ignition required speed;

[0075] S403. Correct the engine ignition speed requirement based on the engine coolant temperature to obtain the engine ignition target speed.

[0076] When the lock-up clutch is locked:

[0077] S404. Obtain the current actual speed of the motor as the required speed for engine ignition.

[0078] S405. Based on the acceleration / deceleration conditions and the second vehicle condition information, the engine ignition required speed is corrected to obtain the engine ignition target speed.

[0079] In the above process, the engine ignition required speed is the theoretically required speed for engine ignition under the current operating conditions. The preset speed value is the default speed required for engine ignition under ideal conditions. When the lock-up clutch is unlocked, due to the characteristics of hydraulic transmission, the impact of the engine starting directly at the preset speed value has a relatively small impact on driving stability. However, when the lock-up clutch is engaged, using the motor speed as the engine ignition required speed makes the engagement between the motor and the engine smoother and reduces shock.

[0080] Furthermore, in a preferred embodiment, the second vehicle condition information includes pedal opening, gear ratio, and vehicle speed, wherein the pedal opening includes accelerator pedal opening and brake pedal opening; step S404 in the above process, correcting the engine ignition demand speed according to the acceleration / deceleration conditions and the second vehicle condition information to obtain the engine ignition target speed, includes:

[0081] If the vehicle is accelerating, the engine ignition speed requirement is adjusted according to the accelerator pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed.

[0082] If the vehicle is decelerating, the engine ignition speed requirement is adjusted according to the brake pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed.

[0083] If the vehicle is moving at a constant speed, then the engine ignition required speed is taken as the engine ignition target speed.

[0084] In this embodiment, when the lock-up clutch is in the locked state, the engine ignition speed requirement is further corrected according to the vehicle's state. That is, the engine ignition speed requirement can be increased or decreased according to the vehicle's acceleration or deceleration, while no correction is made for the engine ignition speed requirement in the constant speed state. Finally, the target engine ignition speed is obtained. This can make up for the difference in actual speed caused by clutch disengagement during the start-up process, further shorten the engine start-up time, and reduce shock.

[0085] Furthermore, the above steps S302, obtaining the engine starting torque based on the engine water temperature and the engine ignition target speed, and S303, obtaining the clutch slip pressure based on the engine starting torque, can all be achieved by any existing technology, and will not be elaborated on in this article.

[0086] Furthermore, in combination Figure 5 As shown, in a preferred embodiment, step S304, which involves correcting the engine starting torque requirement based on the lock-up clutch state, the first vehicle condition information, and the second vehicle condition information, and obtaining the target drive torque for the electric motor based on the driving torque requirement, specifically includes:

[0087] S501. Obtain the first correction coefficient based on the state of the lock-up clutch;

[0088] S502. Based on the acceleration / deceleration conditions, a second correction coefficient is obtained based on the rate of change of the pedal opening.

[0089] S503. Correct the engine starting torque requirement according to the first correction coefficient and the second correction coefficient, and obtain the target driving torque of the motor based on the driving torque requirement.

[0090] In the above process, the first correction coefficient and the second correction coefficient can be adjusted by addition or multiplication according to actual needs to correct the engine starting torque. The corrected engine starting torque takes into account the torque transmission deviation generated when the vehicle accelerates and decelerates and the locking clutch is engaged, so that the actual output torque is more in line with the actual situation, which can shorten the engine speed adjustment time and thus reduce the engine starting time.

[0091] Specifically, in a preferred embodiment, step S501, obtaining the first correction coefficient based on the lock-up clutch state, specifically includes:

[0092] When the locking clutch is unlocked:

[0093] The first correction coefficient is obtained based on the torque transmission characteristics of the lock-up clutch.

[0094] The first correction factor can be a preset value obtained based on the torque transmission characteristics of the lock-up clutch. When the lock-up clutch is locked, there is no engagement process and no torque transmission loss. Therefore, the torque required for engine starting is not corrected based on the torque transmission characteristics of the lock-up clutch. At this time, according to the correction method of the first correction factor, its value can be 1 (corrected by multiplication) or 0 (corrected by addition), etc.

[0095] Specifically, in a preferred embodiment, step S502, obtaining a second correction coefficient based on the pedal opening according to the acceleration / deceleration condition, specifically includes:

[0096] If the vehicle is accelerating, the second correction coefficient is obtained based on the rate of change of the accelerator pedal opening.

[0097] If the vehicle is decelerating, the second correction coefficient is obtained based on the rate of change of the brake pedal opening.

[0098] Unlike the first correction factor, the above process corrects the engine starting torque requirement by adjusting the angle of vehicle acceleration and deceleration. Similarly, when the vehicle is traveling at a constant speed, there is no speed change requirement, so there is no need to correct from the angle of acceleration and deceleration. In this case, according to the correction method of the second correction factor, its value can be 1 (corrected by multiplication) or 0 (corrected by addition), etc.

[0099] Furthermore, in a preferred embodiment, step S203, controlling the slippage between the clutch and the engine based on the clutch slippage pressure, and towing the engine to the engine ignition target speed based on the target drive torque of the motor, specifically includes:

[0100] Real-time acquisition of motor torque;

[0101] If the vehicle is in an acceleration state or a constant speed state, when the real-time torque of the motor is increased to the required torque of the motor, the clutch and the engine are controlled to start slipping according to the clutch slipping pressure.

[0102] If the vehicle is decelerating, the clutch and engine are directly controlled to slip based on the clutch slip pressure.

[0103] The real-time motor torque mentioned above refers to the motor torque detected in real time, specifically the torque output by the motor at the moment the current step is executed. This process can further shorten engine start-up time and reduce shock, while proper clutch slippage timing also ensures vehicle handling.

[0104] Furthermore, in a preferred embodiment, in step S204 above, controlling the clutch to disconnect from the engine includes:

[0105] The clutch is gradually disconnected from the engine, while the torque of the motor is simultaneously controlled to change from the target drive torque to the required driving torque.

[0106] Similarly, the above process can also ensure that engine start-up time is further shortened and shock is reduced, while proper clutch disengagement timing can also ensure vehicle handling.

[0107] Furthermore, in a preferred embodiment, step S205, starting the engine and adjusting its speed until the engine speed reaches a preset condition, and fully engaging the clutch and the engine, includes the following preset conditions:

[0108] When the lock-up clutch is unlocked, the difference between the engine speed and the motor speed is less than the first speed difference;

[0109] When the lock-up clutch is unlocked, the difference between the engine speed and the motor speed is less than the second speed difference;

[0110] Wherein, the second speed difference is smaller than the first speed difference.

[0111] When the engine speed meets the above preset conditions, engaging the clutch can minimize engagement shock and improve driving smoothness.

[0112] The present invention also provides a more detailed embodiment to more clearly illustrate the above steps S201 to S205:

[0113] 1. Collect signals such as SOC, vehicle speed, accelerator pedal opening, and brake pedal opening (i.e., the driving condition information mentioned below; unless otherwise specified, all directly acquired data is assumed to be the driving condition information). Determine if there is an engine start requirement. If there is no engine start requirement, proceed to the next step; otherwise, return to the previous step.

[0114] 2. Determine the driver's acceleration demand based on the accelerator pedal signal. If there is an acceleration demand (i.e., the acceleration condition described in the acceleration / deceleration conditions), further determine whether the lock-up clutch needs to be unlocked based on the current gear and the desired gear. If there is no acceleration demand (i.e., the deceleration condition described in the acceleration / deceleration conditions), determine the driver's deceleration demand based on the brake pedal signal. This provides information such as the lock-up clutch status and acceleration / deceleration conditions.

[0115] (1) Engine starting procedure when the lock-up clutch is unlocked under acceleration conditions:

[0116] A. Continuously acquire the real-time torque Tq of the motor and the torque Tq1 required for driving;

[0117] The preset speed value is directly used as the engine ignition required speed r1, and the ignition speed increment r0 is set according to the engine water temperature. The engine ignition target speed R = r1 + r0 is obtained by correcting r1.

[0118] Calculate the engine starting torque Tq2 required to reach the engine ignition target speed R based on the current engine coolant temperature and the engine ignition target speed R.

[0119] The clutch slip pressure F is calculated based on the engine starting torque Tq2.

[0120] The first correction coefficient Str1 is obtained based on the torque transmission characteristics of the lock-up clutch, and the second correction coefficient Str2 under acceleration conditions is obtained based on the rate of change of the accelerator pedal opening. At this time, the target drive torque Tq3 of the motor is: Tq3=Tq1+Tq2*Str1*Str2;

[0121] Then the motor torque can be adjusted. During the process of the motor real-time torque Tq increasing from the initial value to the motor target drive torque Tq3, when Tq is greater than Tq1, the control clutch starts to slip, and the engine ignites after reaching the engine ignition target speed.

[0122] B. Determine if the engine ignition was successful, and simultaneously determine the lock-up clutch's engagement request:

[0123] i. Engine failed to start, lock-up clutch did not request engagement: Engine ignition continues.

[0124] ii. The engine failed to start and the lock-up clutch requested to be locked: proceed to (3)A. Engine start procedure when the lock-up clutch is locked.

[0125] iii. Once the engine starts successfully, the engine speed is adjusted until the speed difference between the engine and the motor is less than the first speed difference dr1. Then, the clutch is engaged, the clutch is locked, and torque distribution is performed.

[0126] (2) Engine starting procedure when the lock-up clutch is unlocked under deceleration conditions:

[0127] A. Continuously acquire the real-time torque Tq of the motor and the torque Tq1 required for driving. Under deceleration conditions, Tq0 is greater than Tq1.

[0128] The preset speed value is directly used as the engine ignition required speed r1, and the ignition speed increment r0 is set according to the engine water temperature. The engine ignition target speed R = r1 + r0 is obtained by correcting r1.

[0129] Calculate the engine starting torque Tq2 required to reach the engine ignition target speed R based on the current engine coolant temperature and the engine ignition target speed R.

[0130] The clutch slip pressure F is calculated based on the engine starting torque Tq2.

[0131] The first correction coefficient Str1 is obtained based on the torque transmission characteristics of the lock-up clutch, and then the second correction coefficient Str4 under deceleration conditions is obtained based on the rate of change of the brake pedal opening. At this time, the target driving torque Tq3 of the motor is: Tq3=Tq1+Tq2*Str1*Str4;

[0132] Then, the clutch can be directly controlled to start slipping, and at the same time, the real-time torque Tq of the motor changes from the initial value to the target driving torque Tq3. After the engine reaches the target ignition speed, the engine ignites.

[0133] B. Determine if the engine ignition was successful, and simultaneously determine the lock-up clutch's engagement request:

[0134] i. Engine failed to start, lock-up clutch did not request engagement: Engine ignition continues.

[0135] ii. The engine failed to start and the lock-up clutch requested to be locked: proceed to (3)B. Engine start procedure when the lock-up clutch is locked.

[0136] iii. Once the engine starts successfully, the engine speed is adjusted until the speed difference between the engine and the motor is less than the first speed difference dr1. Then, the clutch is engaged, the clutch is locked, and torque distribution is performed.

[0137] (3) Engine starting procedure when the lock-up clutch is engaged:

[0138] A. Under acceleration conditions:

[0139] Continuously acquire the real-time torque Tq of the motor and the torque Tq1 required for driving;

[0140] At this point, the current actual speed Rem of the motor is taken as the engine ignition required speed r1. At the same time, based on the throttle pedal opening, transmission ratio and vehicle speed, the increase in motor speed dr3 during the period from clutch disengagement to engine start is estimated. Then, the engine ignition required speed is corrected to obtain the engine ignition target speed R = r1 + dr3.

[0141] Calculate the engine starting torque Tq2 required to reach the engine ignition target speed R based on the current engine coolant temperature and the engine ignition target speed R.

[0142] The clutch slip pressure F is calculated based on the engine starting torque Tq2.

[0143] At this point, the lock-up clutch is engaged, so the value of the first correction coefficient Str1 can be set to 1. Then, the second correction coefficient Str2 under acceleration conditions is obtained based on the rate of change of the accelerator pedal opening. At this point, the target drive torque Tq3 of the motor is: Tq3 = Tq1 + Tq2 * Str2.

[0144] Then the motor torque can be adjusted. During the process of the motor real-time torque Tq increasing from the initial value to the motor target drive torque Tq3, when Tq is greater than Tq1, the control clutch starts to slip. After the engine reaches the engine ignition target speed, the clutch disengages and enters the (4) engine start and speed adjustment stage.

[0145] B. Under deceleration conditions:

[0146] When the brake pedal is pressed and the lock-up clutch is engaged, the motor performs energy recovery and continuously acquires the real-time motor torque Tq and the driving demand torque Tq1, where the driving demand torque Tq1 is less than 0.

[0147] At this point, the current actual speed Rem of the motor is taken as the engine ignition required speed r1. At the same time, based on the brake pedal opening, transmission ratio and vehicle speed, the decrease in motor speed dr4 during the period from clutch disengagement to engine start is estimated. The engine ignition required speed is then corrected to obtain the engine ignition target speed R = r1 - dr4.

[0148] Calculate the engine starting torque Tq2 required to reach the engine ignition target speed R based on the current engine coolant temperature and the engine ignition target speed R.

[0149] The clutch slip pressure F is calculated based on the engine starting torque Tq2.

[0150] At this time, the lock-up clutch is locked, so the value of the first correction coefficient Str1 can be set to 1. Then, the second correction coefficient Str4 under deceleration condition is obtained according to the rate of change of the brake pedal opening. At this time, the target drive torque Tq3 of the motor is: Tq3=Tq1+Tq2*Str4;

[0151] Then you can directly control the clutch to start slipping, and at the same time the real-time torque Tq of the motor changes from the initial value to the target driving torque Tq3. After the engine reaches the target speed for engine ignition, the clutch disengages and enters the (4) engine start and speed regulation stage.

[0152] C. Under conditions without acceleration or deceleration:

[0153] Continuously acquire the real-time torque Tq of the motor and the torque Tq1 required for driving;

[0154] At this point, the current actual speed Rem of the motor is taken as the engine ignition demand speed r1, and also as the engine ignition target speed R. At this point, the correction amount of the engine ignition demand speed can be regarded as 0.

[0155] Calculate the engine starting torque Tq2 required to reach the engine ignition target speed R based on the current engine coolant temperature and the engine ignition target speed R.

[0156] The clutch slip pressure F is calculated based on the engine starting torque Tq2.

[0157] At this time, the lock-up clutch is engaged, so the value of the first correction coefficient Str1 can be set to 1. At the same time, since there is no need for vehicle speed change, the value of the second correction coefficient can also be set to 1. At this time, the target drive torque Tq3 of the motor is: Tq3 = Tq1 + Tq2.

[0158] Then the motor torque can be adjusted. During the process of the motor real-time torque Tq increasing from the initial value to the motor target drive torque Tq3, when Tq is greater than Tq1, the control clutch starts to slip. After the engine reaches the engine ignition target speed, the clutch disengages and enters the (4) engine start and speed adjustment stage.

[0159] (4) Engine start-up and speed adjustment stage:

[0160] The real-time torque Tq of the motor gradually changes to the driving demand torque Tq1 as the clutch disengages. After the clutch is fully disengaged, the engine is ignited. If the engine starts successfully, the engine speed is adjusted. If the engine fails to start, the ignition continues. The engine speed is controlled to the current speed of the motor. When the speed difference is less than the second speed difference dr2 (dr2 is less than dr1), the clutch is controlled to engage. After engagement, torque distribution is performed.

[0161] The beneficial effects of this embodiment are:

[0162] 1. Based on the state of the lock-up clutch, different engine starting methods are developed to avoid interfering with the driver's acceleration and deceleration needs. Specifically:

[0163] a) If the lock-up clutch is engaged, the P2 motor will lift the engine to a higher speed through clutch slippage, and then the clutch will disengage, allowing the engine to start again. The key point of this method is that when the clutch is disengaged and the engine is started, the engine starting shock will not be transmitted to the transmission system through the clutch. Moreover, compared to starting the engine at idle speed, there is less vibration and noise at high speed. Therefore, combining these two points can effectively improve driving smoothness and comfort.

[0164] b. If the lock-up clutch is unlocked, the P2 motor, through clutch slippage, pulls the engine to a lower speed before starting the engine and then adjusting the speed. The key point of this method is that after engine ignition, the engine's own speed adjustment capability (i.e., speed adjustment through controlling engine fuel injection) and the clutch slippage torque can be combined to shorten the engine speed adjustment time and the mode switching process. Combined with the hydraulic transmission characteristics when the lock-up clutch is open, this can reduce the impact on the transmission system. At the same time, during this process, the clutch is in a slippage state, and the transmitted torque is determined by the clutch oil pressure, thus reducing the impact of torque fluctuations during engine start-up on driving smoothness.

[0165] 2. Based on the vehicle's acceleration and deceleration conditions, different engine starting torques and target starting speeds are set to shorten the starting time, while ensuring that the engine starting process does not affect the normal driving of the vehicle. Specifically:

[0166] a) Under acceleration conditions, a second correction coefficient for the engine starting torque is obtained based on the rate of change of the accelerator pedal opening. This allows for a larger engine starting torque than the actual torque required, thereby increasing the clutch slip pressure, causing the engine speed to increase rapidly and shortening the starting time. Simultaneously, if the lock-up clutch is engaged at this time, and the clutch disengages during the starting process, the increase in motor speed (dr3) during the period from clutch disengagement to engine start is estimated based on the controlled accelerator pedal opening, transmission ratio, and vehicle speed. This allows for adjustment of the engine ignition target speed, shortening the engine speed adjustment time.

[0167] b. Under deceleration conditions, a second correction coefficient for the engine starting torque is obtained based on the rate of change of the brake pedal opening. If there is a demand for energy recovery torque, the negative torque of the engine on the drive motor during engine starting can be used to achieve the deceleration target. Simultaneously, if the lock-up clutch is engaged at this time and disengaged during starting, the reduction in motor speed (dr4) during the period from clutch disengagement to engine starting is estimated based on the brake pedal opening, transmission ratio, and vehicle speed. This allows for adjustment of the engine ignition target speed and shortening of the engine speed adjustment time.

[0168] 3. During the engine start-up process, the engine starting torque is adjusted according to the engine coolant temperature to obtain the clutch slip pressure, and then the appropriate clutch oil pressure is obtained to adapt to different ambient temperatures and engine hot or cold conditions, thereby improving starting efficiency.

[0169] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An engine start-up control method for a parallel P2 hybrid configuration, characterized in that, The parallel P2 hybrid configuration includes an engine, a clutch, an electric motor, and an automatic transmission connected in sequence, wherein the automatic transmission includes a lock-up clutch, and the method includes: Obtain vehicle operating condition information; Based on the driving condition information, the target engine ignition speed, clutch slip pressure, and target motor drive torque are obtained. The clutch slippage pressure is controlled to control the slippage between the clutch and the engine, and the engine is towed up to the engine ignition target speed based on the target drive torque of the motor; Based on the driving condition information, determine whether the lock-up clutch is unlocked. If so, maintain the slipping state between the clutch and the engine, and utilize the hydraulic transmission characteristics when the lock-up clutch is unlocked to reduce the impact on the transmission system during engine start-up. If not, control the clutch to disconnect from the engine. Start the engine and adjust its speed until it reaches a preset speed, then fully engage the clutch and the engine.

2. The engine start-up control method for a parallel P2 hybrid configuration according to claim 1, characterized in that, The driving condition information includes driving demand torque, lock-up clutch status (used to indicate whether the lock-up clutch is unlocked), engine coolant temperature, first vehicle condition information, and second vehicle condition information. The step of obtaining the engine ignition target speed, clutch slip pressure, and electric motor target drive torque based on the driving condition information includes: Based on the state of the lock-up clutch, the target engine ignition speed is obtained by combining the first vehicle condition information and the second vehicle condition information. Based on the engine coolant temperature and the engine ignition target speed, the required engine starting torque is obtained; The clutch slip pressure is obtained based on the engine starting torque requirement; Based on the lock-up clutch status, the engine starting torque is corrected by combining the first vehicle condition information and the second vehicle condition information, and the target drive torque of the motor is obtained by combining the driving torque.

3. The engine start-up control method for a parallel P2 hybrid configuration according to claim 2, characterized in that, The first vehicle condition information includes acceleration and deceleration conditions used to characterize whether the vehicle is accelerating, decelerating, or moving at a constant speed. The step of obtaining the engine ignition target speed based on the lock-up clutch state, combined with the first vehicle condition information and the second vehicle condition information, includes: When the lock-up clutch is unlocked, a preset speed value is obtained as the engine ignition required speed, and the engine ignition required speed is corrected according to the engine coolant temperature to obtain the engine ignition target speed. When the lock-up clutch is locked, the current actual speed of the motor is obtained as the engine ignition required speed, and the engine ignition required speed is corrected according to the acceleration and deceleration conditions and the second vehicle condition information to obtain the engine ignition target speed.

4. The engine start-up control method for a parallel P2 hybrid configuration according to claim 3, characterized in that, The second vehicle condition information includes pedal opening, gear ratio, and vehicle speed, wherein the pedal opening includes accelerator pedal opening and brake pedal opening; The step of correcting the engine ignition demand speed based on the acceleration / deceleration conditions and the second vehicle condition information to obtain the engine ignition target speed includes: If the vehicle is accelerating, the engine ignition speed requirement is adjusted according to the accelerator pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed. If the vehicle is decelerating, the engine ignition speed requirement is adjusted according to the brake pedal opening, the transmission ratio, and the vehicle speed to obtain the engine ignition target speed. If the vehicle is moving at a constant speed, then the engine ignition required speed is taken as the engine ignition target speed.

5. The engine start-up control method for a parallel P2 hybrid configuration according to claim 4, characterized in that, The step of correcting the engine starting torque requirement based on the lock-up clutch state, combined with the first vehicle condition information and the second vehicle condition information, and obtaining the target drive torque of the electric motor based on the driving torque requirement, includes: Based on the state of the lock-up clutch, a first correction coefficient is obtained; Based on the acceleration / deceleration conditions, a second correction coefficient is obtained based on the rate of change of the pedal opening; The engine starting torque is corrected based on the first correction factor and the second correction factor, and the target drive torque of the motor is obtained based on the combined driving torque.

6. The engine start-up control method for a parallel P2 hybrid configuration according to claim 5, characterized in that, The step of obtaining the first correction coefficient based on the lock-up clutch state includes: When the lock-up clutch is unlocked, the first correction coefficient is obtained based on the torque transmission characteristics of the lock-up clutch.

7. The engine start-up control method for a parallel P2 hybrid configuration according to claim 5, characterized in that, The step of obtaining a second correction coefficient based on the pedal opening according to the acceleration / deceleration condition includes: If the vehicle is accelerating, the second correction coefficient is obtained based on the rate of change of the accelerator pedal opening. If the vehicle is decelerating, the second correction coefficient is obtained based on the rate of change of the brake pedal opening.

8. The engine start-up control method for a parallel P2 hybrid configuration according to claim 3, characterized in that, The step of controlling the slippage between the clutch and the engine based on the clutch slippage pressure, and towing the engine to the engine ignition target speed based on the target drive torque of the motor, includes: Real-time acquisition of motor torque; If the vehicle is in an acceleration state or a constant speed state, when the real-time torque of the motor is increased to the required torque of the motor, the clutch and the engine are controlled to start slipping according to the clutch slipping pressure. If the vehicle is decelerating, the clutch and engine are directly controlled to slip based on the clutch slip pressure.

9. The engine start-up control method for a parallel P2 hybrid configuration according to claim 2, characterized in that, The control of disconnecting the clutch from the engine includes: The clutch is gradually disconnected from the engine, while the torque of the motor is simultaneously controlled to change from the target drive torque to the required driving torque.

10. The engine start-up control method for a parallel P2 hybrid configuration according to claim 2, characterized in that, The preset conditions include: When the lock-up clutch is unlocked, the difference between the engine speed and the motor speed is less than the first speed difference; When the lock-up clutch is not unlocked, the difference between the engine speed and the motor speed is less than the second speed difference; Wherein, the second speed difference is smaller than the first speed difference.

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