An injection control method and system for a hybrid vehicle

Abstract

The present invention relates to an injection control method and system for a hybrid vehicle. The injection control method includes the following steps: S1, obtaining the current engine operating point and the target power; S2, calculating the wall impingement energy factor of the current injection timing T according to the operating parameters of the current engine operating point; S3, determining whether wall impingement oil film is generated when the engine switches to the target power. If it is generated, the injection timing is postponed; otherwise, a single early injection mode is used. Compared with the prior art, the present invention judges the in-cylinder air-fuel mixture condition during the operation of the engine during vehicle driving through the injection wall impingement factor, reasonably and accurately switches the working mode of injection, and improves the fuel economy of the hybrid vehicle while ensuring that the emissions meet the requirements of the RDE test.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control, and particularly to an injection control method and system for a hybrid vehicle. Background Art

[0002] A hybrid vehicle has at least two power sources. Generally, one power source is an engine and the other is a battery. Part of the energy required during vehicle driving comes from the internal combustion engine, which converts the chemical energy in the fuel into mechanical energy; the other part comes from the power battery, which converts electrical energy into mechanical energy through a motor. During the driving process of a hybrid vehicle, there are operating modes such as pure electric drive, pure internal combustion engine drive, on-board charging, and hybrid drive. The vehicle controller distributes the vehicle's required power to the engine and the battery.

[0003] After determining the target power value of the engine, injection control is performed by an injection control module. Generally, the engine injection strategy control is mainly based on the look-up table difference method of a Map. However, during transient working conditions such as start-stop, it is difficult to accurately control the fuel injection quantity, resulting in an increase in actual road emissions.

[0004] Existing research mainly focuses on the injection strategy of multiple injections of the engine. For example, the Chinese invention patent with the publication number CN114251182A discloses a dual main injection method. On the premise of meeting economy, it is difficult to coordinate the reliability and emission performance to reach the optimum for the operating conditions of a diesel engine. The Chinese invention patent with the publication number CN110748425A discloses a control method for transient injection quantity. However, after the natural gas injection impacts the inner wall surface of the engine cylinder, no wall-attached oil film is generated, and the impact on emissions is small.

[0005] In summary, the prior art does not consider the transient injection control characteristics of a hybrid vehicle. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide an injection control method and system for a hybrid vehicle, so as to solve the problem that during the actual road driving of a hybrid vehicle under the China VI RDE emission regulations, due to road surface, traffic and other conditions, inaccurate fuel injection and incomplete combustion occur during the engine working condition switching process, resulting in an increase in emissions.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] According to the first aspect of the present invention, an injection control method for a hybrid vehicle is provided, including the following steps:

[0009] S1. Obtain the current engine operating point and the target power;

[0010] S2. Calculate the wall impingement energy factor of the current injection timing T according to the operating parameters of the current engine operating point;

[0011] S3. Determine whether wall impingement oil film is generated when the engine switches to the target power. If so, delay the injection timing; otherwise, use the single early injection mode.

[0012] Further, the wall impingement energy factor E inj is calculated by the formula:

[0013]

[0014] where m air is the intake air volume corresponding to the current engine operating point; C air is the specific heat capacity of the intake air; t air is the intake air temperature corresponding to the current engine operating point; m inj is the fuel injection volume corresponding to the current engine operating point; C fuel is the specific heat capacity of the fuel; t fuel is the current fuel temperature; m wall is the wall impingement oil film volume corresponding to the current engine operating point; t cylinder is the current mixture temperature; t water is the current engine coolant temperature.

[0015] Further, the wall impingement oil film volume m wall is determined by simulation calculation.

[0016] Further, step S3 is specifically: Obtain the preset threshold E demand . If E inj ≥E demand , then wall impingement oil film is generated and the injection timing is delayed; otherwise, E inj <E demand , use the single early injection mode.

[0017] Further, it further includes step S4: The delayed injection timing is T + t'. If T + t' < T 1 , then the second injection mode is enabled. If T + t' ≥ T 1 , then calculate the delayed wall impingement energy factor E inj '. If E inj '<E demand , then use the single late injection mode; otherwise, Er'≥E demand , then continue to delay the injection timing t' and repeat this step, where t' is the delay value of the injection timing and T 1 is the first latest injection timing.

[0018] Further, determine the thresholds for switching different target powers at each operating condition point through experiments, and determine the threshold E for the engine to switch to the target power at the current engine operating condition point by looking up a table. demand 。

[0019] According to the second aspect of the present invention, there is provided an injection control system for a hybrid vehicle, including:

[0020] A data acquisition module for acquiring the current engine operating condition point and the target power;

[0021] A calculation module for calculating the wall impingement energy factor of the current injection timing T according to the operating condition parameters of the current engine operating condition point;

[0022] A control module for determining whether wall impingement oil film is generated when the engine switches to the target power. If so, delay the injection timing. Otherwise, use the single early injection mode.

[0023] Further, the wall impingement energy factor E inj The calculation formula is:

[0024]

[0025] Where m air Is the intake air volume corresponding to the current engine operating condition point; C air Is the specific heat capacity of the intake air; t air Is the intake air temperature corresponding to the current engine operating condition point; m inj Is the fuel injection volume corresponding to the current engine operating condition point; C fuel Is the specific heat capacity of the fuel; t fuel Is the current fuel temperature; m wall Is the wall impingement oil film volume corresponding to the current engine operating condition point; t cylinder Is the current mixture temperature; t water Is the current engine coolant temperature.

[0026] Further, the control of the control module is specifically: obtain the preset threshold E demand , if E inj ≥E demand , then wall impingement oil film is generated and the injection timing is delayed. Otherwise, E inj <E demand , use the single early injection mode.

[0027] Further, the control of the control module further includes: the delayed injection timing is T + t'. If T + t' < T 1 , then turn on the second injection mode. If T + t' ≥ T 1 , then calculate the delayed wall impingement energy factor E inj ’, if E inj’ < E demand If so, use the single - time late injection mode; otherwise, Er’ ≥ E demand If so, continue to postpone the fuel injection timing t’, and repeat this step, where t’ is the postponed value of the fuel injection timing, and T 1 is the earliest latest fuel injection timing.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] By judging the in - cylinder air - fuel mixture condition during the operation of the engine during vehicle driving through the fuel injection wall - hitting factor, reasonably and accurately switch the working mode of fuel injection, and while ensuring that the emissions meet the requirements of the RDE test, improve the fuel economy of hybrid vehicles. Description of the Drawings

[0030] Figure 1 is a schematic diagram of the fuel injection control implementation block diagram in the embodiment;

[0031] Figure 2 is a flowchart of the fuel injection control method in the embodiment;

[0032] Figure 3 is a schematic diagram of the fuel spray wall - hitting simulation. Detailed Embodiments

[0033] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives the detailed implementation method and specific operation process. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The protection scope of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0034] This specification provides the method operation steps such as in the embodiment or the process schematic diagram, but based on routine or non - creative labor, it may include more or fewer operation steps. The step order listed in the embodiment is only one way among the execution orders of numerous steps, and does not represent the only execution order. When the actual system or server product executes, it can be executed in the order shown in the embodiment or the drawings or executed in parallel (for example, in an environment of parallel processors or multi - threaded processing) or adjust the execution order of steps without time sequence restrictions.

[0035] The present invention provides a fuel injection control method for a hybrid vehicle, as Figure 1 and Figure 2 shown, including the following steps:

[0036] S1. Obtain the current engine operating point and the target power;

[0037] Based on input signals such as vehicle sensors and the driver's accelerator pedal, the total required power of the vehicle (i.e., the total target power) is calculated through conversion. The hybrid control unit receives the total target power value of the vehicle, distributes the total target power value and outputs it to the power sources (engine and motor), and outputs the target power value of the engine to the fuel injection control module;

[0038] S2. Calculate the wall impingement energy factor at the current fuel injection timing T according to the operating condition parameters of the current engine operating point;

[0039] Wall impingement energy factor E inj The calculation formula is:

[0040]

[0041] where, m air is the intake air amount corresponding to the current engine operating point; C air is the specific heat capacity of the intake air, 1020 J / kg·°C; t air is the intake air temperature corresponding to the current engine operating point; m inj is the fuel injection amount corresponding to the current engine operating point; C fuel is the specific heat capacity of the fuel, 2200 J / kg·°C for gasoline; t fuel is the current fuel temperature; m wall is the wall impingement oil film amount corresponding to the current engine operating point; t cylinder is the current mixture temperature; t water is the current engine coolant temperature. Among them, the wall impingement oil film amount m wall is determined through simulation calculation, and parameters such as the intake air amount and fuel injection amount can be obtained through the vehicle controller and a series of sensors.

[0042] The fuel injection impinges on the surface, generating an adhering oil film on the piston surface, as Figure 3 shown. Curtis et al. (see the literature E.W. Curtis, C.F. Aquino, D.K. Trumpy, G.C. Davis, 1996. A new port and cylinder wall wetting model to predict transient air / fuel excursions in a port fuel injected engine. SAE Technical Paper, Issue 961186.) defined the fuel wall impingement equation for port fuel injection engines, and the equation is also applicable to direct injection engines:

[0043]

[0044] Where: Sh is the dimensionless Sherwood number, A ls corresponds to the wall-impinging surface area, ρ fuel is the fuel density, D fa corresponds to the mass diffusion coefficient between the fuel and air, ΔMFF is the difference in fuel mass fraction between the wall-adhering oil film and the free incoming flow, MFFs is the fuel mass fraction of the wall-adhering oil film, D p is the cylinder diameter. Assume that the fuel spray is a perfect cone and the piston top is a horizontal plane. Use the spray model and trigonometric functions to estimate relevant geometric features such as the depth and angle of the spray cone, and calculate A ls .

[0045] Taking an engine for a certain hybrid vehicle at 1500 r / min and 10 bar as an example, m air is 3.64×10 -4 kg, the intake air temperature t air is 25°C, t fuel is 19°C, m inj is 2.526×10 -5 kg, the m at the fuel injection timing 300°CA before top dead center wall is 2.66×10 -8 kg, t cylinder is 180°C, t water is 83°C, the current fuel injection timing E inj is calculated to be 6.2. Under the same operating conditions, if it is a cold start and the water temperature is relatively low, E inj is calculated to be 7.8.

[0046] S3. Determine whether the engine switching to the target power generates a wall-impinging oil film. If it does, delay the fuel injection timing; otherwise, use the single early injection mode.

[0047] Specifically: Obtain the pre-set threshold E demand . If E inj ≥E demand , then a wall-impinging oil film is generated and the fuel injection timing is delayed; otherwise, E inj <E demand , use the single early injection mode. Among them, obtaining the threshold E demand is specifically: Determine the thresholds for switching different target powers at each operating condition point through experiments in advance and store them. When the vehicle is running, the threshold E demand for the engine to switch to the target power under the current engine operating condition point can be determined by looking up the table.

[0048] S4. When a wall-impinging oil film is generated and the fuel injection timing is delayed, the delayed fuel injection timing is T + t'. If T + t' < T 1 , then turn on the second fuel injection mode; if T + t' ≥ T 1 , then calculate the delayed wall-impinging energy factor Einj ’, if E inj ’ < E demand , then the single late injection mode is used; otherwise, Er’ ≥ E demand , then continue to postpone the injection timing t’, and repeat this step, where t’ is the postponed value of the injection timing, and T 1 is the first latest injection timing.

[0049] It can be understood that the meanings of the single early injection mode, the delay time t’ of the injection timing, the second injection mode, the single late injection mode, etc. are well-known to those skilled in the art. For example, the delay time t’ of the injection timing can be determined by the engine factory parameters, etc., and will not be elaborated here.

[0050] Among them, the formula for the post-collision wall energy factor E inj ’ remains unchanged. However, after the delayed injection, the piston moves downward, the in-cylinder space increases, the collision wall distance of the injection becomes longer, and the amount of the collision wall oil film m wall becomes less, thus changing the value of the collision wall energy factor.

[0051] S5. The vehicle control unit obtains the actual engine power at the current engine operating point according to the actual engine fuel injection amount of the engine, and then performs power distribution calculation on the vehicle target output power to calculate the actual required power of the motor, completing the optimization adjustment. That is, in this application, the target fuel injection amount of the engine is compared with the actual fuel injection amount through the injection collision wall energy factor to determine whether the power switching to the target power exceeds the injection collision wall threshold, and then adjust to the appropriate injection timing, output the actual power of the engine, and then correct the target power of the motor.

[0052] This application judges the in-cylinder air-fuel mixture condition during the operation of the engine during vehicle driving through the injection collision wall factor, reasonably and accurately switches the injection working mode, and improves the fuel economy of the hybrid vehicle while ensuring that the emissions meet the requirements of the RDE test.

[0053] This application realizes the precise control of the injection timing, enables the injected fuel to burn fully in the cylinder, and then ensures that the discharged exhaust gas can meet the standard limits of the RDE emissions; at the same time, it also avoids the problem of increased engine fuel consumption and increased emissions caused by excessive fuel injection in some working conditions due to incomplete combustion of the excessive fuel, and realizes the optimization of the power economy of the hybrid vehicle on the basis of meeting the reduction of engine emissions.

[0054] The present invention also provides an injection control system for a hybrid vehicle, including:

[0055] A data acquisition module, configured to acquire the current engine operating point and the target power;

[0056] A calculation module, configured to calculate a wall impingement energy factor at the current fuel injection timing T according to the operating parameters of the current engine operating point;

[0057] A control module, configured to determine whether wall impingement oil film is generated when the engine switches to the target power. If so, the fuel injection timing is postponed; otherwise, a single early injection mode is used.

[0058] The wall impingement energy factor E inj has the following calculation formula:

[0059]

[0060] where, m air is the intake air volume corresponding to the current engine operating point; C air is the specific heat capacity of the intake air; t air is the intake air temperature corresponding to the current engine operating point; m inj is the fuel injection volume corresponding to the current engine operating point; C fuel is the specific heat capacity of the fuel; t fuel is the current fuel temperature; m wall is the wall impingement oil film volume corresponding to the current engine operating point; t cylinder is the current mixture temperature; t water is the current engine coolant temperature.

[0061] The control of the control module is specifically as follows: Obtain a preset threshold value E demand . If E inj ≥E demand , then wall impingement oil film is generated and the fuel injection timing is postponed; otherwise, E inj <E demand , and a single early injection mode is used.

[0062] The control of the control module further includes: The postponed fuel injection timing is T + t'. If T + t' < T 1 , then a second fuel injection mode is enabled. If T + t' ≥ T 1 , then calculate the postponed wall impingement energy factor E inj '. If E inj ' < E demand , then a single late injection mode is used; otherwise, Er' ≥ E demand , then continue to postpone the fuel injection timing by t' and repeat this step, where t' is the postponement value of the fuel injection timing and T 1 is the earliest latest fuel injection timing.

[0063] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the described modules can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0064] This application uses the fuel injection wall-impingement energy factor to quickly and accurately estimate the engine fuel injection, and corrects the motor target power based on the engine output power at the actual fuel injection moment. It improves the situation of excessive fuel injection under some transient conditions of the existing engine, takes into account the power performance and fuel economy of the vehicle while effectively reducing emissions, and achieves a double reduction in fuel consumption and emissions.

[0065] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. An injection control method for a hybrid vehicle, characterized in that, it includes the following steps: S1. Obtain the current engine operating point and the target power; S2. Calculate the wall impingement energy factor at the current injection time T according to the operating parameters of the current engine operating point; S3. Determine whether wall impingement oil film is generated when the engine switches to the target power. If it is generated, delay the injection time. Otherwise, use the single early injection mode; The wall-collision energy factor E inj is calculated by the following formula: where, m air is the intake air volume corresponding to the current engine operating point; C air is the specific heat capacity of the intake air; t air is the intake air temperature corresponding to the current engine operating point; m inj is the fuel injection volume corresponding to the current engine operating point; C fuel is the specific heat capacity of the fuel; t fuel is the current fuel temperature; m wall is the wall impingement fuel film volume corresponding to the current engine operating point; t cylinder is the current mixture temperature; t water is the current engine cooling water temperature; Step S3 specifically is: Obtain a preset threshold value E demand , if E inj ≥E demand , then generate a wall-impinging oil film and delay the fuel injection timing; otherwise, if E inj <E demand , use the single early injection mode.

2. The injection control method for a hybrid vehicle according to claim 1, characterized in that, The wall-hitting oil film quantity m wall is determined by simulation calculation.

3. The injection control method for a hybrid vehicle according to claim 1, characterized in that, It further includes step S4: the postponed fuel injection timing is T + t'. If T + t' < T 1 , then the second fuel injection mode is enabled. If T + t' ≥ T 1 , then calculate the postponed wall-impingement energy factor E inj '. If E inj ' < E demand , then use the single late injection mode. Otherwise, Er' ≥ E demand , then continue to postpone the fuel injection timing t' and repeat this step, where t' is the postponement value of the fuel injection timing and T 1 is the earliest latest fuel injection timing.

4. The injection control method for a hybrid vehicle according to claim 1, characterized in that, Determine the thresholds for switching different target powers at each operating condition point through experiments, and determine the threshold E for the engine to switch to the target power at the current engine operating condition point by looking up a table. demand .

5. An injection control system for a hybrid vehicle, characterized in that, it includes: A data acquisition module for obtaining the current engine operating point and the target power; A calculation module for calculating the wall impingement energy factor at the current injection time T according to the operating parameters of the current engine operating point; A control module for determining whether wall impingement oil film is generated when the engine switches to the target power. If it is generated, delay the injection time. Otherwise, use the single early injection mode; The wall-collision energy factor E inj is calculated by the following formula: Among them, m air is the intake air volume corresponding to the current engine operating point; C air is the specific heat capacity of the intake air; t air is the intake air temperature corresponding to the current engine operating point; m inj is the fuel injection volume corresponding to the current engine operating point; C fuel is the specific heat capacity of the fuel; t fuel is the current fuel temperature; m wall is the wall-impinged oil film volume corresponding to the current engine operating point; t cylinder is the current mixture temperature; t water is the current engine cooling water temperature; The control of the control module is specifically as follows: obtaining a preset threshold E demand , if E inj ≥E demand , then a wall-hitting oil film is generated and the fuel injection timing is postponed; otherwise, E inj <E demand , and a single early injection mode is used.

6. The injection control system for a hybrid vehicle according to claim 5, characterized in that, The control of the control module further includes: the injection timing after postponement is T + t', if T + t' < T 1 , then the second injection mode is enabled, if T + t' ≥ T 1 , then calculate the wall-impingement energy factor E inj ' after postponement. If E inj ' < E demand , then the single late injection mode is used. Otherwise, Er' ≥ E demand , then continue to postpone the injection timing t', and repeat this step, where t' is the postponement value of the injection timing, and T 1 is the first latest injection timing.

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