Engine starting method and device in dual-motor hybrid power system and vehicle

Abstract

The present invention provides a method and device for starting an engine in a dual-motor hybrid power system and a vehicle, belonging to the field of vehicle technology. The dual-motor hybrid power system includes an engine, a first motor connected to the engine, and a clutch connected between the first motor and a transmission system. The starting method includes: upon receiving an engine start request, obtaining the current state of the first motor; if the current state of the first motor is a fault, obtaining the current state data of the vehicle, the current state data of the vehicle including the current speed of the vehicle; determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the conditions for waiting for the clutch to start; if so, monitoring the speed of the vehicle in real time until the speed of the vehicle is greater than the preset speed threshold to control the clutch to drag the engine to start. The present invention can improve the NVH performance and stability of the vehicle when the engine is started.

Description

[0001] This application is a divisional application of the Chinese invention application with application number 202110018057.4, application date January 7, 2021, and invention name “Engine starting method and device and vehicle in a dual-motor hybrid system”. Technical Field

[0002] The present invention relates to the technical field of vehicles, and in particular to a method and device for starting an engine in a dual-motor hybrid power system and a hybrid power vehicle. Background Art

[0003] With the increasingly stringent requirements of various countries on vehicle fuel consumption and emissions and the development of electrification systems, hybrid technology has become the key to achieving vehicle energy conservation and emission reduction. Due to the complexity and high cost of the battery technology of the current pure electric system, hybrid systems are being vigorously promoted. The dual-motor hybrid system is a high-efficiency hybrid system. Its general structure is as follows: Figure 1 As shown. Dual-motor hybrid systems generally have three engine starting methods: 12V starter drag engine start (referred to as 12V start), P1 motor drag engine start (referred to as P1 motor start) and clutch C0 drag engine start (referred to as clutch start). Under normal circumstances, dual-motor hybrid systems use P1 motor start, and in the event of a P1 motor failure, 12V start or clutch start is selected according to the vehicle speed. In particular, when the vehicle speed is less than or equal to the preset vehicle speed threshold (such as 10km / h), 12V start will be used. However, when starting with 12V, the noise is large and the oscillation is also large, the vehicle's NVH (Noise-Vibration-Harshness, noise, vibration and sound roughness) performance and stability are poor, and the user experience is not good. Therefore, there is an urgent need for a method for starting the engine in a dual-motor hybrid system that can improve NVH performance and stability. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a method and device for starting an engine in a dual-motor hybrid system and a hybrid vehicle that overcome the above problems or at least partially solve the above problems.

[0005] An object of the present invention is to provide a method for starting an engine in a dual-motor hybrid system, which can improve the NVH performance and smoothness of the vehicle when the engine is started.

[0006] A further object of the present invention is to improve the smoothness and safety during clutch startup.

[0007] In particular, according to one aspect of an embodiment of the present invention, a method for starting an engine in a dual-motor hybrid system is provided, wherein the dual-motor hybrid system includes an engine, a first motor connected to the engine, and a clutch connected between the first motor and a transmission system; the starting method includes:

[0008] When receiving an engine start request, obtaining a current state of the first motor;

[0009] If the current state of the first motor is a fault, obtaining current state data of the vehicle, wherein the current state data of the vehicle includes a current speed of the vehicle;

[0010] Determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the clutch activation waiting condition;

[0011] If the current speed of the vehicle is less than or equal to the preset speed threshold and other current status data of the vehicle meets the waiting clutch start condition, the vehicle speed is monitored in real time until the vehicle speed is greater than the preset speed threshold, then the clutch is controlled to drag the engine to start.

[0012] Optionally, the clutch activation waiting condition includes a condition that the vehicle is accelerating and a condition that the vehicle does not need the engine to run all the time.

[0013] Optionally, the current state data of the vehicle further includes acceleration or throttle opening and a driving mode of the vehicle;

[0014] The conditions for the vehicle to have acceleration requirements include:

[0015] The acceleration is positive and greater than a preset acceleration threshold; or

[0016] The throttle opening is greater than a second throttle opening threshold;

[0017] The conditions under which the vehicle does not need the engine to run all the time include:

[0018] The driving mode of the vehicle is not equal to the sport mode.

[0019] Optionally, the current state data of the vehicle further includes a driver requested torque;

[0020] The clutch start waiting condition also includes:

[0021] The driver requested torque is less than a second wheel end torque threshold.

[0022] Optionally, the current state data of the vehicle further includes engine speed and throttle state or driver requested torque;

[0023] The controlling the clutch to drag the engine to start includes:

[0024] determining whether the engine speed is less than or equal to a preset speed threshold, and determining a starting mode intended by the driver according to the throttle state or the driver's requested torque;

[0025] If the engine speed is less than or equal to the preset speed threshold and the starting mode intended by the driver is a smooth starting mode, a drag start signal is generated and sent to the clutch, and the clutch is controlled to output a corresponding pre-drag torque within a set time period from the receipt of the drag start signal.

[0026] Optionally, the current state data of the vehicle further includes a coolant temperature and a throttle state of the engine or a driver requested torque;

[0027] The controlling the clutch to drag the engine to start includes:

[0028] determining a start mode intended by a driver according to the throttle state or the driver requested torque;

[0029] determining a fuel injection timing of the engine according to a coolant temperature of the engine and a start mode intended by the driver;

[0030] During the process of the clutch dragging the engine to start, the engine is controlled to inject fuel at the determined injection time.

[0031] Optionally, the throttle state includes a throttle opening and a throttle change rate;

[0032] The step of determining the starting mode intended by the driver according to the throttle state or the driver's requested torque comprises:

[0033] Determining whether the throttle opening is greater than a first throttle opening threshold and the throttle change rate is greater than a preset change rate threshold;

[0034] If so, determining that the start mode intended by the driver is a quick start mode;

[0035] If not, determining that the start mode intended by the driver is a smooth start mode; or,

[0036] determining whether the driver's requested torque is greater than a first wheel-end torque threshold;

[0037] If so, determining that the start mode intended by the driver is a quick start mode;

[0038] If not, it is determined that the start mode intended by the driver is a smooth start mode.

[0039] Optionally, the step of determining the injection timing of the engine according to the coolant temperature of the engine and the starting mode intended by the driver comprises:

[0040] When the start mode intended by the driver is a quick start mode, determining the injection time of the engine to be a time when the speed of the engine is greater than 0;

[0041] When the start mode intended by the driver is a smooth start mode and the coolant temperature of the engine is greater than a preset hot engine start temperature, determining the injection time of the engine to be the time when the drag torque of the clutch is completely unloaded;

[0042] When the starting mode intended by the driver is the smooth starting mode and the coolant temperature of the engine is less than or equal to the preset hot engine starting temperature, the correspondence table between the coolant temperature of the engine and the torque limit of the clutch is looked up to obtain the target torque limit of the clutch corresponding to the coolant temperature of the engine, and the injection time of the engine is determined to be the time when the drag torque of the clutch is less than the target torque limit.

[0043] According to another aspect of an embodiment of the present invention, a starting device for an engine in a dual-motor hybrid system is provided, comprising a memory and a processor, wherein a control program is stored in the memory, and when the control program is executed by the processor, it is used to implement any of the starting methods described above.

[0044] According to another aspect of an embodiment of the present invention, a hybrid vehicle is provided, including a dual-motor hybrid system and a starting device for an engine in the dual-motor hybrid system as described above.

[0045] In the method and device for starting the engine in the dual-motor hybrid system proposed in the embodiment of the present invention, in the case of a failure of the first motor (i.e., the P1 motor), if the current speed of the vehicle is less than or equal to the preset speed threshold and the current state of the vehicle meets the clutch start waiting condition, the vehicle speed is monitored in real time until the vehicle speed is greater than the preset speed threshold, and then the clutch C0 is controlled to drag the engine to start (i.e., the clutch start waiting strategy). The present invention defines a clutch start waiting strategy after the P1 motor fails. Even if there is an engine start request when the P1 motor fails and the vehicle speed is less than or equal to the preset speed threshold, the 12V start is not performed. Instead, the clutch is started until the vehicle speed increases to greater than the preset speed threshold to meet the clutch start speed condition, thereby avoiding the noise and oscillation generated during 12V starting and improving the NVH performance and smoothness of the engine start.

[0046] Furthermore, during the process of clutch dragging the engine to start (i.e., clutch start), by controlling the clutch to output the corresponding pre-drag torque within a set time period from the receipt of the drag start signal when the pre-drag torque application conditions are met, the impact caused by the rapid increase of the drag torque during the starting process is avoided, thereby effectively improving the smoothness of the engine start.

[0047] Furthermore, during the clutch starting process, by controlling the engine's injection timing according to the engine's coolant temperature and the driver's intended starting mode, it is possible to prevent starting shock, starting failure or engine speed drop caused by premature or late engine injection, thereby improving the smoothness and safety of engine starting.

[0048] Furthermore, during the clutch starting process, by performing active damping control on the second motor (ie, the drive motor), it is possible to prevent the second motor from shaking during the clutch starting process, thereby further improving the starting smoothness.

[0049] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below.

[0050] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0052] Figure 1 It is a structural schematic diagram of a dual-motor hybrid system;

[0053] Figure 2 for Figure 1 The schematic diagram of the dual-motor hybrid system shown is when the clutch is activated;

[0054] Figure 3 It is a schematic flow chart of a method for starting an engine in a dual-motor hybrid power system according to the first embodiment of the present invention;

[0055] Figure 4 It is a schematic flow chart of a method for starting an engine in a dual-motor hybrid power system according to a second embodiment of the present invention;

[0056] Figure 5 This is a schematic diagram of the starting effect after the pre-drag torque is used when the P1 motor is started;

[0057] Figure 6 It is a schematic diagram of the starting effect when the P1 motor is started without using the pre-drag torque in the prior art;

[0058] Figure 7 It is a schematic flow chart of a method for starting an engine in a dual-motor hybrid power system according to a third embodiment of the present invention;

[0059] Figure 8 Schematic diagram of each stage in the process of starting the P1 motor in the fourth embodiment of the present invention;

[0060] Fig. 9 The figure is a schematic diagram of the structure of a starting device for an engine in a dual-motor hybrid system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0062] The dual-motor hybrid system is currently the key technology to achieve vehicle energy conservation and emission reduction. Figure 1 As shown, the dual-motor hybrid system generally includes an engine 1, a first motor 2 ( Figure 1 denoted as P1), and a clutch 3 ( Figure 1 The transmission system 5 is connected to the wheel 6. The dual-motor hybrid system may further include a battery 4 connected to the first motor 2. Furthermore, the dual-motor hybrid system may further include a second motor 7 ( Figure 1 The second motor 7 is connected to the transmission system 5 and is also connected to the battery 4 and the clutch 3 .

[0063] The dual-motor hybrid system generally has three modes: pure electric mode, series mode and parallel mode. In the series mode, the clutch C0 is not engaged, the engine 1 charges the battery 4 through the first motor 2 (i.e., the P1 motor), and the battery 4 supplies power to the second motor 7 (i.e., the P2 motor) so that the P2 motor drives the wheels 6. In the parallel mode, the clutch C0 is engaged, and the engine 1 and the P2 motor directly drive the wheels 6 at the same time.

[0064] As mentioned above, dual-motor hybrid systems generally have three engine starting methods: 12V starter drag engine 1 start (abbreviated as 12V start, 12V starter in Figure 1 In the example shown in Figure 1, the P1 motor starts the engine 1 (referred to as the P1 motor start) and the clutch C0 starts the engine 1 (referred to as the clutch start). Under normal circumstances, the dual-motor hybrid system uses the P1 motor to start. In the event of a P1 motor failure, the 12V start or clutch start is selected according to the current vehicle speed. When the clutch is started, if Figure 2 As shown, clutch C0 is engaged, and engine 1 is started by dragging clutch C0. Figure 2 The black arrow in indicates the transmission direction of the drag torque.

[0065] However, in the prior art, when starting at 12V, there is a lot of noise and oscillation, the NVH performance and stability of the vehicle are poor, and the user experience is not good.

[0066] To solve or at least partially solve the above technical problems, an embodiment of the present invention provides a method for starting an engine in a dual-motor hybrid system. The technical solutions in the embodiments of the present invention will be clearly and completely described below through embodiments 1 to 4 of the present invention.

[0067] Embodiment 1

[0068] The structure of the dual-motor hybrid system in this embodiment is as follows: Figure 1 As shown, it includes an engine 1, a first motor 2 (ie, P1 motor) connected to the engine 1, and a clutch 3 (ie, clutch C0) connected between the first motor 2 and a transmission system 5.

[0069] See also Figure 3 As shown, the method for starting the engine in the dual-motor hybrid system of this embodiment may at least include the following steps S302 to S308.

[0070] Step S302, when the engine start request is received, obtaining the current state of the first motor 2.

[0071] Step S304: if the current state of the first motor 2 is a fault, the current state data of the vehicle is acquired, and the current state data of the vehicle includes the current speed of the vehicle.

[0072] Step S306, determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the waiting clutch start condition. If so, that is, the current speed of the vehicle is less than or equal to the preset speed threshold and other current state data of the vehicle meets the waiting clutch start condition, it can be considered that the waiting clutch start strategy can be enabled, and step S308 is executed.

[0073] In this step, the preset vehicle speed threshold is the maximum vehicle speed allowed for a 12V start attempt under normal circumstances, and can be set according to the actual application configuration parameters of the vehicle, for example, it can be set to 10km / h.

[0074] Step S308, monitoring the vehicle speed in real time, and controlling the clutch 3 to drag the engine 1 to start when the vehicle speed is greater than a preset speed threshold.

[0075] In the engine starting method in the dual-motor hybrid system proposed in the embodiment of the present invention, by defining a waiting clutch starting strategy after a P1 motor failure, even if there is an engine start request when the P1 motor fails and the vehicle speed is less than or equal to a preset vehicle speed threshold, 12V starting is not performed. Instead, the clutch is started until the vehicle speed increases to a speed greater than the preset vehicle speed threshold to meet the vehicle speed condition for clutch starting, thereby avoiding the noise and oscillation generated during 12V starting and improving the NVH performance and smoothness of the engine starting.

[0076] Furthermore, the clutch start waiting condition may include a condition that the vehicle is accelerating and a condition that the vehicle does not need the engine to be running all the time. When the vehicle acceleration condition is met, it can be ensured that the vehicle can reach the speed required for clutch start in a relatively short time, avoiding the inability to ensure the normal operation of the vehicle due to too long waiting time. When the vehicle does not need the engine to be running all the time, the rationality of the clutch start waiting strategy can be ensured to ensure the normal operation of the vehicle.

[0077] Specifically, the current state data of the vehicle may also include acceleration or throttle opening (also referred to as accelerator pedal opening) and the vehicle's driving mode. Accordingly, the conditions under which the vehicle has an acceleration requirement include: the acceleration is positive (i.e., the vehicle has positive acceleration) and is greater than a preset acceleration threshold, or the throttle opening is greater than a second throttle opening threshold (indicating that the accelerator pedal is in an activated state). The preset acceleration threshold and the second throttle opening threshold can be set according to actual application requirements. For example, the preset acceleration threshold can be set to 0.4 m / s 2 , the second throttle opening threshold can be set to 5%. The conditions under which the vehicle does not need the engine to run all the time include: the vehicle's driving mode is not equal to the sports mode. Hybrid vehicles usually have multiple driving modes, such as energy-saving mode, normal mode, sports mode, etc. In the sports mode, the engine is required to run all the time to ensure the high power demand of the sports mode. Therefore, the waiting clutch start strategy cannot be enabled in the sports mode.

[0078] Of course, the current state data of the vehicle can also be obtained simultaneously with the current state of the first motor 2, that is, the current state data of the first motor 2 and the current state data of the vehicle are obtained simultaneously in step S302. In this case, if the current state of the first motor 2 is a fault, step S306 is executed.

[0079] In a further embodiment, the current state data of the vehicle may also include the driver's requested torque. The driver's requested torque refers to the wheel torque requested by the driver. Accordingly, the waiting clutch start condition may also include: the driver's requested torque is less than the second wheel-end torque threshold. The second wheel-end torque threshold can be set according to actual application requirements, for example, it can be set to 1000N·m. When the driver's requested torque is low, it indicates that the user's required start response speed is low. In this case, enabling the waiting clutch enable strategy can improve NVH performance and smoothness while minimizing the impact on the user's acceleration driving experience.

[0080] In addition, if Figure 1 As shown, the dual-motor hybrid system of this embodiment may also include a second motor 7 (i.e., P2 motor) connected to the transmission system 5 for driving the wheel 6. Since the second motor 7 drives the wheel 6, the second motor 7 may also be referred to as a drive motor. Since during the clutch starting process, the second motor 7 needs to compensate for the loss of clutch starting in addition to driving the wheel 6, the second motor 7 may generate vibration, thereby affecting the starting smoothness. In order to prevent the vibration of the second motor 7 during the clutch starting process, the engine starting method in the dual-motor hybrid system of this embodiment may also include the following steps: in the process of controlling the clutch 3 to drag the engine 1 to start, the second motor 7 is actively damped.

[0081] Specifically, the step of performing active damping control on the second motor 7 may include:

[0082] Acquire the requested speed of the driver and the actual speed of the second motor 7;

[0083] Calculate the difference between the requested speed and the actual speed;

[0084] Proportional-Integral (PI) control is performed on the second motor 7 according to the difference, so as to compensate for the output torque of the second motor 7 .

[0085] Proportional-integral control is a commonly used control strategy and will not be introduced in detail in this article.

[0086] This embodiment can prevent the second motor 7 from shaking during the clutch starting process by performing active damping control on the second motor 7 during the clutch starting process, thereby further improving the starting smoothness.

[0087] Embodiment 2

[0088] The difference between this embodiment and the first embodiment is that when the waiting clutch start strategy is enabled to start the clutch, a prefill torque strategy is executed on the clutch 3 .

[0089] Reference Figure 4 As shown, the method for starting the engine in the dual-motor hybrid system of this embodiment may at least include the following steps S402 to S412.

[0090] Step S402, when the engine start request is received, obtaining the current state of the first motor 2.

[0091] Step S404: if the current state of the first motor 2 is a fault, the current state data of the vehicle is acquired, and the current state data of the vehicle at least includes the current speed of the vehicle.

[0092] Step S406, determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the waiting clutch activation condition. If so, that is, the current speed of the vehicle is less than or equal to the preset speed threshold and other current state data of the vehicle meets the waiting clutch activation condition, then executing step S408.

[0093] Step S408, monitoring the vehicle speed in real time until the vehicle speed is greater than a preset speed threshold.

[0094] Step S410, judging whether the pre-tug torque application condition is met according to the current state data of the vehicle. If so, executing step S412.

[0095] Step S412, generating a drag start signal and sending it to the clutch 3, so as to control the clutch 3 to drag the engine 1 to start, and control the clutch 3 to output the corresponding pre-drag torque within a set time period from receiving the drag start signal.

[0096] This embodiment controls the clutch C0 to output the corresponding pre-drag torque within a set time period after receiving the drag start signal when the pre-drag torque application condition is met, so that the clutch C0 can first drag the engine 1 to a certain speed with the pre-drag torque before the drag torque of the clutch C0 increases to the maximum to drag the engine 1 to the target speed. In this way, the drag torque of the clutch C0 will not rise directly to the maximum, but will first reach an intermediate value (i.e., the value of the pre-drag torque) and then reach the maximum, which can avoid the impact caused by the excessive increase of the drag torque during the starting process, thereby effectively improving the smoothness of the engine starting.

[0097] In step S404 above, the current state data of the vehicle may include the speed of the engine 1 and the throttle state or the driver's requested torque. Accordingly, the pre-tug torque application condition mentioned in step S410 may include: the speed of the engine 1 is less than or equal to the preset speed threshold and the driver's intended start mode is a smooth start mode, wherein the driver's intended start mode can be determined based on the throttle state or the driver's requested torque. The preset speed threshold can be set based on the result of actual vehicle calibration based on the actual parameters of the engine 1. When the speed of the engine 1 is greater than the preset speed threshold, the pre-tug torque cannot drag the engine 1. Specifically, the preset speed threshold can be set to 50rpm, for example.

[0098] In the above step S410, the start mode intended by the driver can be determined according to the throttle state or the driver's requested torque, and then it can be determined whether the engine 1 speed and the start mode intended by the driver meet the pre-tug torque application condition. In a specific implementation, the throttle state may include the throttle opening and the throttle change rate. In this case, judging the start mode intended by the driver according to the throttle state or the driver's requested torque can be specifically implemented as follows: judging the start mode intended by the driver according to the acquired throttle opening and throttle change rate, or according to the acquired driver's requested torque. Specifically, it is determined whether the throttle opening is greater than the first throttle opening threshold and the throttle change rate is greater than the preset change rate threshold. If so, it is determined that the start mode intended by the driver is a fast start mode. If not (that is, the throttle opening is less than or equal to the first throttle opening threshold, or the throttle change rate is less than or equal to the preset change rate threshold), it is determined that the start mode intended by the driver is a smooth start mode. Alternatively, determine whether the driver's requested torque is greater than the first wheel-end torque threshold. If so, determine that the driver's intended starting mode is the quick starting mode. If not (that is, the driver's requested torque is less than or equal to the first wheel-end torque threshold), determine that the driver's intended starting mode is the smooth starting mode.

[0099] Further, in step S410, it is determined whether the acquired engine 1 speed is less than or equal to a preset speed threshold and whether the start mode intended by the driver is a smooth start mode. If the engine 1 speed is less than or equal to the preset speed threshold and the start mode intended by the driver is a smooth start mode, step S412 is executed.

[0100] In this embodiment, the first throttle opening threshold and the preset change rate threshold can be set to 70% and 300% / s, respectively. The first wheel-end torque threshold is related to the current speed of the vehicle. In this way, the current speed of the vehicle can also be obtained as one of the current state data of the vehicle in step S404, and then the first wheel-end torque threshold is determined according to the current speed of the vehicle. Specifically, according to the current speed of the vehicle, by looking up the relationship table between the vehicle speed and the wheel-end torque limit, the wheel-end torque limit corresponding to the current speed of the vehicle can be obtained as the first wheel-end torque threshold. The following Table 1 exemplarily shows the relationship table between the vehicle speed and the wheel-end torque limit.

[0101] Table 1 Relationship between vehicle speed and wheel end torque limit

[0102] Vehicle speed (km / h) 3 10 20 30 50 100 Wheel end torque limit (N·m) 1500 600 235 200 150 100

[0103] When looking up the table, for the current vehicle speed that falls between the various speed points in the relationship table between the vehicle speed and the wheel end torque limit, the wheel end torque limit corresponding to the current vehicle speed can be calculated by interpolation.

[0104] In this embodiment, by accurately judging whether the pre-drag torque application condition is met according to the engine 1 speed and the throttle state or the driver's requested torque, the effectiveness of the pre-drag torque in improving the smoothness during the engine 1 starting process can be ensured.

[0105] In step S412 above, the set duration can be within the range of 0.2-0.4s. When the clutch 3 (i.e., the clutch C0) is used as the target component for dragging the engine 1 to start, the corresponding pre-drag torque can be set according to the actual vehicle calibration result when the vehicle is started. The setting of the pre-drag torque corresponding to the clutch C0 should ensure that the clutch C0 can be completely engaged, so it can be preferably set to 2-4N·m.

[0106] It should be noted that step S410 can be performed at any time after step S406 and before step S412. For example, step S410 can be performed during real-time monitoring of the vehicle speed. If it is determined that the pre-drag torque application conditions are met, step S412 is executed when the vehicle speed is greater than a preset speed threshold.

[0107] Although the above only describes the pre-drag torque strategy when the clutch 3 is used as the target component for dragging the engine 1 to start, those skilled in the art should understand that when the first motor 2 (i.e., the P1 motor) is used as the target component for dragging the engine 1 to start, its working principle and effect are similar to those of the pre-drag torque strategy of the clutch 3. After applying the pre-drag torque, the drag torque of the target component rises to the maximum value to drag the engine 1 to reach the target speed and start the engine 1. In this way, the drag torque of the target component is prevented from directly increasing to the maximum, thereby improving the smoothness. The following is an example of starting the P1 motor. Figure 5 The figure shows the starting effect after the pre-drag torque is used when the P1 motor starts. Figure 6 The figure shows the starting effect of the P1 motor in the prior art when the pre-drag torque is not used. Figure 5 , from the moment the P1 motor receives the drag start signal (set to 0s), the P1 motor outputs a pre-drag torque, which reaches 20N·m at 0.1s and remains at 20N·m from 0.1s to 0.2s, thereby dragging the engine 1 to a certain speed. After 0.2s, the pre-drag torque is gradually unloaded, and the pre-drag torque drops to 0 at 0.4s. At the same time, after 0.2s, the drag torque output by the P1 motor increases to the maximum value to drag the engine 1 to the target speed. After the engine 1 reaches the target speed, the drag torque of the P1 motor is unloaded. In contrast, Figure 6 After receiving the drag start signal, the P1 motor has no pre-drag torque, and its drag torque increases directly to the maximum value. Figure 5 and Figure 6 , Figure 5 The fluctuation range of vehicle acceleration during the startup process is 0.16m / s 2 ,and Figure 6 During the startup process, the fluctuation range of the vehicle's acceleration reaches 0.23m / s 2 ,compared to Figure 5 The fluctuation range of acceleration is 0.07m / s larger 2 It can be seen that by adopting the pre-drag torque strategy, the impact of the engine 1 starting can be significantly reduced and the starting smoothness can be improved. Those skilled in the art can understand that the starting effect after using the pre-drag torque when the clutch is started is different from Figure 5 The starting effect after using the pre-drag torque when the P1 motor is started is similar, the only difference is that the pre-drag torque of the clutch C0 is 2-4N·m.

[0108] Embodiment 3

[0109] The difference between this embodiment and the first embodiment is that when the waiting clutch start strategy is enabled to start the clutch, the injection time of the engine 1 is also controlled in a targeted manner.

[0110] Reference Figure 7 As shown, the method for starting the engine in the dual-motor hybrid system of this embodiment may at least include the following steps S702 to S716.

[0111] Step S702, when the engine start request is received, obtaining the current state of the first motor 2.

[0112] Step S704, if the current state of the first motor 2 is a fault, the current state data of the vehicle is obtained, and the current state data of the vehicle at least includes the current speed of the vehicle and the coolant temperature of the engine 1 (usually the cooling water temperature of the engine 1).

[0113] Step S706, determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the waiting clutch activation condition. If so, that is, the current speed of the vehicle is less than or equal to the preset speed threshold and other current state data of the vehicle meets the waiting clutch activation condition, then executing step S708.

[0114] Step S708, monitoring the vehicle speed in real time.

[0115] Step S710: When the vehicle speed is greater than a preset vehicle speed threshold, a drag start signal is generated and sent to the clutch 3 to control the clutch 3 to drag the engine 1 to start.

[0116] Step S712: determine the start mode intended by the driver based on the current state data of the vehicle.

[0117] Step S714, determining the injection time of the engine 1 corresponding to the clutch 3 according to the coolant temperature of the engine 1 and the starting mode intended by the driver.

[0118] Step S716, controlling the engine 1 to inject fuel at the determined injection time during the process of the clutch 3 dragging the engine 1 to start.

[0119] The embodiment of the present invention can determine the starting mode intended by the driver based on the current state data of the vehicle, and further determine the injection time of the engine 1 corresponding to the clutch C0 according to the coolant temperature of the engine 1 and the starting mode intended by the driver, so as to specifically control the time when the engine 1 starts to inject fuel during the clutch starting process, prevent the starting shock, starting failure or engine 1 speed drop caused by the engine 1 injecting fuel too early or too late, and further improve the smoothness and safety of the engine 1 starting.

[0120] In this embodiment, the implementation of step S706 is the same as step S406 in embodiment 1, and will not be described in detail.

[0121] In step S704 above, the current state data of the vehicle may also include the throttle state or the driver's requested torque. Further, the throttle state may include the throttle opening and the throttle change rate.

[0122] Accordingly, the startup mode intended by the driver in step S712 may include a quick startup mode and a smooth startup mode. Specifically, the step of determining the startup mode intended by the driver according to the current state data of the vehicle may be implemented as follows: determining whether the throttle opening is greater than the first throttle opening threshold and the throttle change rate is greater than the preset change rate threshold; if so, determining that the startup mode intended by the driver is a quick startup mode; if not (i.e., the throttle opening is less than or equal to the first throttle opening threshold, or the throttle change rate is less than or equal to the preset change rate threshold), determining that the startup mode intended by the driver is a smooth startup mode. Alternatively, determining whether the driver's requested torque is greater than the first wheel-end torque threshold; if so, determining that the startup mode intended by the driver is a quick startup mode; if not, determining that the startup mode intended by the driver is a smooth startup mode. The first throttle opening threshold, the preset change rate threshold, and the first wheel-end torque threshold are defined as described in Example 2 and will not be repeated here.

[0123] In a specific implementation scheme, the above step S714 can be implemented as follows:

[0124] When the start mode intended by the driver is the quick start mode, the injection time of the engine 1 is determined to be the time when the speed of the engine 1 is greater than 0;

[0125] When the start mode intended by the driver is the smooth start mode and the coolant temperature of the engine 1 is greater than the preset hot engine start temperature, the injection time of the engine 1 is determined to be the time when the drag torque of the clutch 3 is completely unloaded;

[0126] When the driver's intended starting mode is the smooth starting mode and the coolant temperature of the engine 1 is less than or equal to the preset hot engine starting temperature, the correspondence table between the engine coolant temperature and the torque limit of the clutch 3 (may be referred to as the second correspondence table) is looked up to obtain the target torque limit of the clutch 3 corresponding to the coolant temperature of the engine 1, and the injection time of the engine 1 is determined to be the time when the drag torque of the clutch 3 is less than the target torque limit.

[0127] Furthermore, in the second correspondence table, the engine coolant temperature is inversely proportional to the torque limit of the clutch 3. The engine coolant temperature and the corresponding torque limit in the above second correspondence table are calibrated according to the actual vehicle performance. The torque limit corresponding to each temperature is the critical value that when the engine coolant temperature is below the preset hot engine start temperature, the clutch 3 drag torque reaches the limit value and no oil injection may cause start failure or engine speed drop. The preset hot engine start temperature can be set according to the property parameters of the engine 1 in actual application, and can generally be set to 60°C.

[0128] Table 2 below exemplarily shows a second correspondence table between the coolant temperature of the engine and the torque limit value of the clutch C0 .

[0129] Table 2 The second correspondence table between the engine coolant temperature and the torque limit of the clutch C0

[0130] Engine coolant temperature (℃) -5 10 25 35 45 60 Torque limit (N·m) 75 65 55 50 45 -3

[0131] In one practical application scheme, the coolant temperature and the torque limit in the second correspondence table are in a one-to-one linear relationship. When looking up the table, the engine coolant temperature that falls between the temperature points in Table 2 can be calculated by interpolation to obtain the torque limit corresponding to the engine coolant temperature. In another practical application scheme, the coolant temperature range in the second correspondence table corresponds to the torque limit. For example, the torque limit corresponding to the temperature range less than or equal to -5°C is 75N·m, the torque limit corresponding to the temperature range greater than -5°C and less than or equal to 10°C is 65N·m, and so on. When looking up the table, the torque limit corresponding to the engine coolant temperature is determined according to the temperature range in which the engine coolant temperature is located.

[0132] Further, in one embodiment, after determining the injection time of the engine 1 under different circumstances, the above step S716 can be implemented in different circumstances. Specifically, when the start mode intended by the driver is the quick start mode, the current speed of the engine 1 is obtained in real time during the process of the clutch 3 dragging the engine 1 to start; when the current speed of the engine 1 is greater than 0, the engine 1 is controlled to inject fuel. When the start mode intended by the driver is the smooth start mode, the drag torque of the clutch 3 is obtained in real time during the process of the clutch 3 dragging the engine 1 to start; when the coolant temperature of the engine 1 is greater than the preset hot engine start temperature, when the drag torque of the clutch 3 is completely unloaded, the engine 1 is controlled to inject fuel; when the coolant temperature of the engine 1 is less than or equal to the preset hot engine start temperature, when the drag torque of the clutch 3 is less than the target torque limit, the engine 1 is controlled to inject fuel. In this embodiment, the standard for the complete unloading of the drag torque of the clutch 3 can be set according to the actual application requirements. Generally, when the drag torque of the clutch 3 is less than the preset torque lower limit, it can be considered that the drag torque of the clutch 3 has been completely unloaded. In one example, the preset torque lower limit value of the clutch 3 may be set to -3 N·m, that is, when the drag torque of the clutch 3 is less than -3 N·m, it can be considered that the drag torque of the clutch 3 is completely unloaded.

[0133] In this embodiment, for the quick start mode, the injection time of the engine 1 is the time when the speed of the engine 1 is greater than 0, that is, the engine 1 does not delay the injection, thereby ensuring the response speed of the quick start. For the smooth start mode and the coolant temperature of the engine 1 is greater than the preset hot engine start temperature (i.e. hot engine start), the injection time of the engine 1 is the time when the drag torque of the clutch 3 is completely unloaded, that is, the engine 1 delays until the drag torque is completely unloaded before injecting (maybe defined as delayed injection), which can avoid the disturbance impact caused by the incomplete unloading of the torque of the clutch 3 and improve the starting smoothness. For the smooth start mode and the coolant temperature of the engine 1 is less than or equal to the preset hot engine start temperature (i.e. cold engine start), the injection time of the engine 1 is the time when the drag torque of the clutch 3 is less than the target torque limit. Since the engine 1 does not need to wait for the drag torque to be completely unloaded before injecting, but can start injecting when the drag torque of the clutch 3 is less than the corresponding target torque limit (maybe defined as early injection), it prevents the engine 1 from falling in speed or starting failure.

[0134] Of course, those skilled in the art should be aware that step S716 in this embodiment is executed during the process of clutch 3 dragging engine 1 to start, especially in the smooth start mode, whether controlling the engine 1 to delay fuel injection or advance fuel injection, it is executed in the process of unloading the drag torque after the clutch 3 drags the engine 1 to reach the target speed.

[0135] Embodiment 4

[0136] The difference between this embodiment and the second embodiment is that when the waiting clutch start strategy is enabled to start the clutch, in addition to executing the pre-drag (prefill) torque strategy for the clutch 3, the injection time of the engine 1 is also specifically controlled. Specifically, the engine starting method in the dual-motor hybrid system of this embodiment may at least include the following steps:

[0137] (1) When receiving the engine start request, obtain the current state of the first motor 2. If the current state of the first motor 2 is faulty, execute (2); if the current state of the first motor 2 is normal, execute (11).

[0138] (2) Acquire the current state data of the vehicle, which at least includes the current vehicle speed, the rotation speed of the engine 1 and the coolant temperature of the engine 1. Then execute (3).

[0139] (3) Determine whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the waiting clutch start condition. If so, that is, the current speed of the vehicle is less than or equal to the preset speed threshold and other current state data of the vehicle meets the waiting clutch start condition, execute (4).

[0140] (4) Monitor the vehicle speed in real time. Then execute (5).

[0141] (5) Determine the start mode intended by the driver based on the current state data of the vehicle. Then execute (6).

[0142] The steps for determining the start mode intended by the driver are as described above.

[0143] (6) Determine whether the pre-tug torque application condition is met based on the engine 1 speed and the driver's intended starting mode. If yes, execute (7); if no, execute (8).

[0144] The steps for determining whether the pre-drag torque application conditions are met are as described above.

[0145] (7) When the vehicle speed is greater than the preset speed threshold, a first drag start signal is generated and sent to the clutch 3 to control the clutch 3 to drag the engine 1 to start, and the clutch 3 is controlled to output the corresponding pre-drag torque within a set time period after receiving the first drag start signal. Then, (9) is executed.

[0146] (8) When the vehicle speed is greater than the preset vehicle speed threshold, a second drag start signal is generated and sent to the clutch 3 to control the clutch 3 to drag the engine 1 to start. Then, (9) is executed.

[0147] In this step, when the pre-drag torque application condition is not satisfied, the clutch is started by the existing pre-drag torque-free method.

[0148] (9) The injection timing of the engine 1 corresponding to the clutch 3 is determined according to the coolant temperature of the engine 1 and the start mode intended by the driver. Then, (10) is executed.

[0149] (10) During the process of the clutch 3 dragging the engine 1 to start, the engine 1 is controlled to inject fuel at the determined injection time, thereby completing the starting of the engine 1.

[0150] (11) Acquire the current state data of the vehicle, the current state data of the vehicle at least including the rotation speed of the engine 1 of the vehicle and the coolant temperature of the engine 1. Then execute (12).

[0151] (12) Determine the start mode intended by the driver based on the current state data of the vehicle. Then execute (13).

[0152] (13) Determine whether the pre-tug torque application condition is met based on the engine 1 speed and the start mode intended by the driver. If yes, execute (14); if not, execute (15).

[0153] The steps for determining whether the pre-drag torque application conditions are met are as described above.

[0154] (14) Generate a third drag start signal and send it to the first motor 2 to control the first motor 2 to drag the engine 1 to start, and control the first motor 2 to output the corresponding pre-drag torque within a set time period after receiving the third drag start signal. Then execute (16).

[0155] (15) Generate a fourth drag start signal and send it to the first motor 2 to control the first motor 2 to drag the engine 1 to start. Then, execute (16).

[0156] (16) The injection timing of the engine 1 corresponding to the first motor 2 is determined according to the coolant temperature of the engine 1 and the start mode intended by the driver. Then, (17) is executed.

[0157] (17) When the first motor 2 is used to start the engine 1, the engine 1 is controlled to inject fuel at the determined injection time, thereby completing the starting of the engine 1.

[0158] In this embodiment, steps (12) and (13) when the first motor 2 is used as the target component for starting the drag engine 1 are the same as steps (5) and (6) when the clutch 3 is used as the target component for starting the drag engine 1. Step (14) is similar to step (7), except that the pre-drag torque corresponding to the first motor 2 is 15-30 N·m. In addition, step (16) is similar to step (9), except that: the preset torque lower limit value of the first motor 2 is different from the preset torque lower limit value of the clutch 3, which can be set to 10 N·m; and when the corresponding target torque limit value is obtained by looking up the table according to the coolant temperature of the engine 1, the correspondence table between the coolant temperature of the engine and the torque limit value of the first motor 2 (i.e., the P1 motor) is used as the basis (which may be referred to as the first correspondence table). In the first correspondence table, the coolant temperature of the engine is also inversely proportional to the torque limit value of the first motor 2. The engine coolant temperature and the corresponding torque limit in the first correspondence table are calibrated according to the actual vehicle performance. The torque limit corresponding to each temperature is the critical value that when the engine coolant temperature is below the preset hot engine start temperature, the drag torque of the first motor 2 reaches the limit and no fuel injection may cause start failure or engine speed drop. The following Table 3 exemplarily shows the first correspondence table between the engine coolant temperature and the torque limit of the P1 motor.

[0159] Table 3 The first correspondence between the engine coolant temperature and the torque limit of the P1 motor

[0160] Engine coolant temperature (℃) -5 10 25 35 45 60 Torque limit (N·m) 75 65 55 50 45 10

[0161] The lookup method of the first correspondence table is the same as that of the second correspondence table, and will not be described in detail.

[0162] This embodiment defines a strategy for waiting for clutch start after a P1 motor failure, and combines the pre-drag torque strategy and fuel injection strategy in P1 motor start or clutch start, which can effectively improve the smoothness and safety of engine 1 start.

[0163] In this embodiment, after the pre-drag torque strategy and the injection strategy are combined together, the process of P1 motor or clutch C0 dragging the engine 1 to start can be divided into the following four stages: (1) the pre-drag stage, during which the P1 motor or clutch C0 outputs a pre-drag torque to drag the engine 1 to a certain speed; (2) the engine drag stage, during which the P1 motor or clutch C0 drags the engine 1 to reach the target speed; (3) the torque unloading stage, during which the drag torque of the P1 motor or clutch C0 is unloaded to about the preset torque lower limit; (4) the engine injection stage, during which the engine 1 starts to inject fuel. Figure 8The above four stages in the process of starting the P1 motor in this embodiment are exemplarily shown. Those skilled in the art can understand that the above four stages also exist in the process of starting the clutch in this embodiment.

[0164] Based on the same technical concept, the embodiment of the present invention also provides a starting device 100 for an engine in a dual-motor hybrid power system. Fig. 9 As shown, the starting device 100 includes a memory 110 and a processor 120. The memory 110 stores a control program, and when the control program is executed by the processor 120, it is used to implement the engine starting method in the dual-motor hybrid system of any embodiment or combination of embodiments described above.

[0165] The starting device of this embodiment defines a waiting clutch starting strategy after a P1 motor failure. Even if there is an engine start request when the P1 motor fails and the vehicle speed is less than or equal to the preset speed threshold, 12V starting is not performed. Instead, the clutch is started only when the vehicle speed increases to a level greater than the preset speed threshold and the clutch starting condition is met. This avoids the noise and oscillation generated during 12V starting and improves the NVH performance and smoothness of the engine starting.

[0166] Based on the same technical concept, the embodiment of the present invention also provides a hybrid vehicle, including a dual-motor hybrid system and an engine starting device 100 in the dual-motor hybrid system described in the above embodiment. Figure 1 shown.

[0167] According to any one of the above optional embodiments or a combination of multiple optional embodiments, the embodiments of the present invention can achieve the following beneficial effects:

[0168] In the method and device for starting the engine in the dual-motor hybrid system proposed in the embodiment of the present invention, in the case of a failure of the first motor 2 (i.e., the P1 motor), if the current speed of the vehicle is less than or equal to the preset speed threshold and the current state of the vehicle meets the clutch start waiting condition, the vehicle speed is monitored in real time until the vehicle speed is greater than the preset speed threshold, and then the clutch C0 is controlled to drag the engine to start (i.e., the clutch start waiting strategy). The present invention defines a clutch start waiting strategy after the P1 motor fails. Even if there is an engine start request when the P1 motor fails and the vehicle speed is less than or equal to the preset speed threshold, the 12V start is not performed. Instead, the clutch is started until the vehicle speed increases to greater than the preset speed threshold to meet the clutch start speed condition, thereby avoiding the noise and oscillation generated during 12V starting and improving the NVH performance and stability of the engine start.

[0169] Furthermore, during the process of clutch dragging the engine to start (i.e., clutch start), by controlling the clutch to output the corresponding pre-drag torque within a set time period from the receipt of the drag start signal when the pre-drag torque application conditions are met, the impact caused by the rapid increase of the drag torque during the starting process is avoided, thereby effectively improving the smoothness of the engine start.

[0170] Furthermore, during the clutch starting process, by controlling the engine's injection timing according to the engine's coolant temperature and the driver's intended starting mode, it is possible to prevent starting shock, starting failure or engine speed drop caused by premature or late engine injection, thereby improving the smoothness and safety of engine starting.

[0171] Furthermore, during the clutch starting process, by performing active damping control on the second motor (ie, the drive motor), it is possible to prevent the second motor from shaking during the clutch starting process, thereby further improving the starting smoothness.

[0172] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that within the spirit and principles of the present invention, the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate from the protection scope of the present invention.

Claims

1. A method for starting an engine in a dual-motor hybrid system, the dual-motor hybrid system comprising an engine, a first motor connected to the engine, and a clutch connected between the first motor and a transmission system; characterized in that: The startup method comprises: When receiving an engine start request, obtaining a current state of the first motor; If the current state of the first motor is a fault, obtaining current state data of the vehicle, wherein the current state data of the vehicle includes a current speed of the vehicle; Determining whether the current speed of the vehicle is less than or equal to a preset speed threshold and whether other current state data of the vehicle meets the clutch activation waiting condition; If the current speed of the vehicle is less than or equal to the preset speed threshold and other current state data of the vehicle meets the clutch start waiting condition, the vehicle speed is monitored in real time until the vehicle speed is greater than the preset speed threshold and the clutch is controlled to start the engine; The current state data of the vehicle further includes engine speed and throttle state or driver requested torque; The controlling the clutch to drag the engine to start includes: determining whether the engine speed is less than or equal to a preset speed threshold, and determining a starting mode intended by the driver according to the throttle state or the driver's requested torque; If the engine speed is less than or equal to the preset speed threshold and the starting mode intended by the driver is a smooth starting mode, a drag start signal is generated and sent to the clutch, and the clutch is controlled to output a corresponding pre-drag torque within a set time period from the receipt of the drag start signal.

2. The startup method according to claim 1, characterized in that: The clutch activation waiting conditions include a condition that the vehicle is accelerating and a condition that the vehicle does not need the engine to be running all the time.

3. The startup method according to claim 1, characterized in that: The current state data of the vehicle also includes a driver requested torque; The clutch start waiting condition also includes: The driver requested torque is less than a second wheel end torque threshold.

4. The startup method according to claim 1, characterized in that: The current state data of the vehicle also includes the coolant temperature and throttle state of the engine or the driver's requested torque; The controlling the clutch to drag the engine to start includes: determining a start mode intended by a driver according to the throttle state or the driver requested torque; determining a fuel injection timing of the engine according to a coolant temperature of the engine and a start mode intended by the driver; During the process of the clutch dragging the engine to start, the engine is controlled to inject fuel at the determined injection time.

5. The starting method according to claim 1 or 4, characterized in that: The throttle state includes the throttle opening and the throttle change rate; The step of determining the starting mode intended by the driver according to the throttle state or the driver's requested torque comprises: Determining whether the throttle opening is greater than a first throttle opening threshold and the throttle change rate is greater than a preset change rate threshold; If so, determining that the start mode intended by the driver is a quick start mode; If not, determining that the start mode intended by the driver is a smooth start mode; or, determining whether the driver's requested torque is greater than a first wheel-end torque threshold; If so, determining that the start mode intended by the driver is a quick start mode; If not, it is determined that the start mode intended by the driver is a smooth start mode.

6. The startup method according to claim 5, characterized in that: The step of determining the injection timing of the engine according to the coolant temperature of the engine and the start mode intended by the driver comprises: When the start mode intended by the driver is a quick start mode, determining the injection time of the engine to be a time when the speed of the engine is greater than 0; When the start mode intended by the driver is a smooth start mode and the coolant temperature of the engine is greater than a preset hot engine start temperature, determining the injection time of the engine to be the time when the drag torque of the clutch is completely unloaded; When the starting mode intended by the driver is the smooth starting mode and the coolant temperature of the engine is less than or equal to the preset hot engine starting temperature, the correspondence table between the coolant temperature of the engine and the torque limit of the clutch is looked up to obtain the target torque limit of the clutch corresponding to the coolant temperature of the engine, and the injection time of the engine is determined to be the time when the drag torque of the clutch is less than the target torque limit.

7. A starting device for an engine in a dual-motor hybrid system, characterized in that: The method comprises a memory and a processor, wherein a control program is stored in the memory, and when the control program is executed by the processor, it is used to implement the startup method according to any one of claims 1 to 6.

8. A hybrid vehicle, characterized in that: It comprises a dual-motor hybrid power system and a starting device for an engine in the dual-motor hybrid power system according to claim 7.

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