CN111016876B

CN111016876B - Engine torque control strategy and system for single-motor hybrid electric vehicle

Info

Publication number: CN111016876B
Application number: CN201911236459.0A
Authority: CN
Inventors: 张剑锋; 姜博; 王来钱; 郭思阳; 杨超群
Original assignee: Zhejiang Geely Holding Group Co Ltd; Zhejiang Geely Automobile Research Institute Co Ltd
Current assignee: Zhejiang Geely Holding Group Co Ltd; Zhejiang Geely Automobile Research Institute Co Ltd
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2021-02-19
Anticipated expiration: 2039-12-05
Also published as: CN111016876A

Abstract

The invention provides an engine torque control strategy and system of a single-motor hybrid vehicle, and belongs to the technical field of hybrid vehicles. The method solves the problems that the fuel consumption of a power assembly is large and the fuel economy is low after the required torque is increased to be larger than the target torque of the engine in the previous control period in the prior art. An engine torque control strategy for a single motor hybrid vehicle, comprising the steps of: A. setting a control mode; B. entering a control mode; C. obtaining a current target torque; D. and calculating the torque of the motor. The single-motor hybrid electric vehicle engine torque control system comprises a vehicle control unit, wherein the vehicle control unit is connected with an engine controller for sending an engine state and an actual engine torque, and the vehicle control unit is further connected with a motor controller, a gearbox controller, an accelerator opening sensor and a vehicle speed sensor. The invention can ensure the torque demand response speed of the vehicle and simultaneously ensure the fuel economy of the power assembly to be high.

Description

Engine torque control strategy and system for single-motor hybrid electric vehicle

Technical Field

The invention belongs to the technical field of hybrid vehicles, and relates to a single-motor hybrid vehicle engine torque control strategy and system.

Background

The power system of the hybrid electric vehicle consists of a plurality of power sources, and in order to realize the fuel economy and the cleanness and environmental protection of the vehicle on the premise of keeping good dynamic property, all parts of the power system need to be coordinately controlled. The hybrid electric vehicle is provided with a power assembly, an engine of the power assembly, a motor, a power battery, a clutch, a gearbox and the like. The single-motor hybrid vehicle is that only one motor is arranged in a power assembly of the hybrid vehicle, and the motor charges a power battery when outputting negative torque and provides driving force for the vehicle when outputting positive torque.

After an engine of the hybrid electric vehicle is started, a vehicle control unit of the hybrid electric vehicle calculates an engine target torque according to a required torque of a driver to control an actual torque of the engine, one engine target torque is obtained in each control cycle of the vehicle control unit, the initial value output of the engine target torque is zero when the engine is just started, and then the engine target torque is changed according to the required torque. When the driver demand torque is increased and is larger than the engine target torque output in one control cycle on the vehicle control unit, the engine torque needs to be controlled, and the motor torque needs to be controlled in order to meet the response speed of the demand torque, namely, when the driver demand torque is increased and is larger than the engine target torque output in one control cycle on the vehicle control unit, the engine torque and the motor torque need to be dynamically distributed. As shown in the conventional torque distribution method and torque distribution controller for a hybrid electric vehicle disclosed in chinese patent application No. CN201710428557.9, under the condition that a power system is in a torque driving mode, an engine is in an operating state, and an electric system meets preset power generation assistance, an original demand torque is obtained by analyzing according to an opening degree of an accelerator pedal, the original demand torque is subjected to drivability processing to obtain a driver demand torque, an engine steady-state demand torque is calculated according to the original demand torque, the engine steady-state demand torque is used as an execution torque of the engine, and when an actual torque of the engine is the same as an execution torque of the engine and the demand torque increases more than the actual torque of the engine, a difference between the two is used as the execution torque of the motor.

Although the execution torque of the engine can be kept unchanged when the required torque is larger than the execution torque of the engine and the assisting power of the motor is sufficient, the motor is preferentially used for compensating the difference value between the required torque and the actual torque of the engine, so that the fuel economy of the engine can be improved to a certain extent, the difference value is completely compensated by the torque of the motor, namely the torque of the motor is supplemented by the increase and the change of the required torque of the engine, the energy of the working of the motor is used for a power battery, the electric quantity of the power battery is compensated by the consumption of the fuel of the engine, and meanwhile, when the power battery supplies power to the motor, the chemical energy of the power battery needs to be converted into electric energy, the electric energy of the motor is converted into mechanical energy, and then the mechanical energy is transmitted to wheels through a gearbox, so that the energy loss on a link is large, so that a large amount of power battery power is consumed when the motor torque compensates for the difference due to the above-mentioned reasons. After the power battery consumes too much power, the engine divides torque to charge the power battery, and energy loss on a link for converting mechanical energy of the engine into electric energy to be transmitted to the power battery for charging is also large, so that in the prior art, although the fuel consumption rate of the engine is not high when the change of the required torque is increased, higher fuel consumption of the engine is needed to supplement the electric quantity, and the fuel consumption of a power assembly of the prior control strategy is larger, so that the problem of lower fuel economy is caused.

Disclosure of Invention

The invention provides a single-motor hybrid vehicle engine torque control strategy and a single-motor hybrid vehicle engine torque control system aiming at the problems in the prior art, and solves the technical problem of ensuring the response speed of the required torque of a vehicle and simultaneously ensuring the fuel economy of a power assembly to be high.

The invention is realized by the following technical scheme: an engine torque control strategy for a single motor hybrid vehicle, the strategy comprising the steps of:

A. setting a control mode: the method comprises the steps that a control mode of engine torque is preset by a vehicle controller, a slope limit table is arranged in the control mode, the control mode comprises a first control mode with a first slope limit table and a second control mode with a second slope limit table, a target torque increase slope limit value of an engine is obtained by checking the corresponding slope limit table according to actual engine torque in the control mode, and the target torque increase slope limit value of the engine obtained by checking the first slope limit table according to the same actual engine torque is smaller than the target torque increase slope limit value of the engine obtained by checking the second slope limit table;

B. entering a control mode: the method comprises the steps that when an engine runs and the current required torque is larger than the target torque of the engine obtained in the last control cycle of a vehicle controller, a control mode is entered, then the first control mode is entered when the change rate of an accelerator pedal meets the change condition and a motor has large power-assisting capacity, and the second control mode is entered when the condition of the first control mode is not met;

C. obtaining the current target torque: after entering a control mode, obtaining an engine target torque increase slope limit value through the currently obtained actual torque of the engine, calculating through the engine target torque increase slope limit value and the current required torque to obtain a current engine target torque, and sending the current engine target torque to an engine controller;

D. calculating the torque of the motor: and obtaining the motor assisting torque according to the currently obtained actual torque of the engine, the required torque, the engine gear and the motor gear, and sending the motor assisting torque to the motor controller.

In the engine torque control strategy of the single-motor hybrid vehicle, when the engine runs and the current required torque is larger than the target torque of the engine obtained in the last control cycle of the vehicle controller, the current engine torque cannot meet the requirement of the current driving torque of a driver, and at the moment, the vehicle enters a control mode. The vehicle control unit can retrieve the target torque of the engine obtained in the last control cycle from the self storage module. After the control mode is entered, the engine target torque increase slope limit value obtained by checking the slope limit value table I under the same actual engine torque is smaller than the engine target torque increase slope limit value obtained by checking the slope limit value table II, so that when other calculated variables are the same and the change rate of the required torque is larger than the engine target torque increase slope limit value, the engine target torque obtained by calculating the engine target torque increase slope limit value obtained by checking the slope limit value table I is smaller than the engine target torque obtained by calculating the engine target torque increase slope limit value obtained by checking the slope limit value table II, namely the rising rate of the engine target torque calculated by checking the slope limit value table I is smaller, the engine target torque rises more stably, and the accurate control of the engine torque is facilitated, while the specific fuel consumption is lower. The lookup slope limit table has a plurality of engine target torque increase slope limits therein. Engine target torque increase slope limit: the parameter is used for limiting the increase rate of the target engine torque sent to the engine controller by the vehicle control unit, when the increase rate of the required torque is smaller than or equal to the parameter, the target engine torque is sent according to the required torque, and when the increase rate of the required torque is larger than the parameter, the increase rate of the target engine torque is limited by the parameter.

After the control mode is entered, whether the control mode is entered into the first control mode or the second control mode, the current engine target torque is calculated, namely the engine target torque of the whole vehicle controller in the control cycle, because the engine target torque is calculated by the engine target torque increase slope limit value and the current required torque, the calculated engine target torque also changes along with the change of the obtained actual engine torque and the change of the required torque, the engine target torque also increases along with the increase of the required torque when the required torque increases, the actual engine torque increases along with the increase of the engine target torque, namely, the actual engine torque changes along with the change of the required engine torque in the control mode. The vehicle control unit sends the target torque of the engine to the engine controller, and the engine controller takes the currently received target torque of the engine as a torque control target of the engine. And the motor power-assisted torque is also calculated, and the motor also responds to the current torque required by the driver, so that the response speed of the required torque to the vehicle is ensured. Therefore, after the torque control strategy enters the control mode, when the required torque is increased, the motor outputs the motor power-assisted torque for assisting, the actual torque of the engine is gradually increased to meet the increase of the required torque, the motor does not need to supplement the increase of the total required torque independently, and the power consumption of the motor assistance is greatly reduced. Therefore, the direct-drive proportion of the vehicle power assembly is increased, energy loss is reduced, power consumption of motor assistance is greatly reduced, energy consumption of power battery supplement is reduced, fuel consumption is low, and fuel economy of the power assembly is high while the torque demand response speed of the vehicle is guaranteed.

In the above-mentioned engine torque control strategy for a single-motor hybrid vehicle, in said step a, the slope limit table one has a plurality of different engine actual torques, two adjacent engine actual torques form an engine actual torque range, the engine target torque increase slope limit value with the lowest fuel consumption rate is obtained by the fuel consumption rate experiment for each engine actual torque, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to each engine actual torque is put into a slope limit value table I, determining the actual torque range of the engine in the first slope limit value table according to the magnitude of the actual torque of the engine obtained currently when inquiring the slope limit value table, and obtaining an engine target torque increase slope limit value corresponding to the currently obtained actual torque of the engine according to an interpolation algorithm. The method does not need to fill the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to all the actual torques of the engine in the slope limit value table, thereby reducing the difficulty of making the table, and simultaneously finding the corresponding engine target torque increase slope limit value with low fuel consumption of the engine through different actual torques of the engine.

In the above-mentioned strategy for controlling the engine torque of the single-motor hybrid vehicle, in step a, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to different actual engine torques is selected as the engine target torque increase slope limit value in the slope limit value table one. The first slope limit table is provided with a plurality of engine target torque increase slope limits, each engine target torque increase slope limit corresponds to one engine actual torque, the corresponding engine target torque increase slope limit with the lowest fuel consumption rate is found according to the currently obtained engine actual torque through the method, and then the calculated engine target torque is the target torque of the engine with the lowest fuel consumption, so that the fuel consumption rate can be kept at a lower level when the engine torque is increased.

In the single-motor hybrid vehicle engine torque control strategy, in the step B, the accelerator pedal change rate is calculated, and when the accelerator pedal change rate is less than or equal to a change threshold value, it is determined that the accelerator pedal change rate meets a change condition, otherwise, a control mode two is entered; the method comprises the steps of obtaining the electric quantity of a power battery, entering a control mode II when the electric quantity of the power battery is judged to be smaller than or equal to an electric quantity threshold value, obtaining the discharge peak power of the power battery, entering the control mode II when the discharge peak power is judged to be smaller than or equal to a discharge threshold value, obtaining the output peak power of a motor, entering the control mode II when the output peak power of the motor is smaller than or equal to the peak threshold value, and judging that the motor has large power-assisting capacity when the electric quantity of the power battery is larger than the electric quantity threshold value, the discharge peak power is larger than the discharge threshold. When the change rate of the accelerator pedal is higher than the change threshold, the current torque demand rise change rate is larger, at the moment, a slope limit table which enables the rise rate of the target torque of the engine to be smaller needs to consume larger electric quantity for assisting, and the motor assisting torque is difficult to compensate the difference part of the actual torque and the demand torque of the engine due to too fast electric quantity consumption in the motor assisting process, so that the response speed is reduced. When the electric quantity of the power battery is smaller than or equal to an electric quantity threshold value, the output peak power of the motor is smaller than or equal to a discharge peak value threshold value, or the discharge peak power of the power battery is smaller than or equal to a discharge threshold value, the motor power-assisted capacity is required to be reduced rapidly by increasing the torque rise rate of the engine, so that the response speed is ensured, when the change rate of an accelerator pedal is smaller than or equal to a change threshold value, the electric quantity of the power battery is larger than an electric quantity threshold value, the discharge peak power of the motor is larger than a discharge peak value threshold value, and the change rate of the accelerator pedal meets a change condition, and the motor has large power-assisted capacity, so that a first control mode is entered, and the target.

In the engine torque control strategy of the single-motor hybrid electric vehicle, the current required torque is larger than the target torque of the engine obtained in the last control period of the whole vehicle controller, and the control mode II is directly entered after the closing signal of the full accelerator switch of the accelerator pedal is received. After receiving the closing signal of the full accelerator switch of the accelerator pedal, the accelerator pedal is indicated to be completely stepped on and then continues to be deeply stepped on, the requirement of the driver on the response speed of the required torque is indicated to be very high, the current control mode is switched to the control mode II at the moment, and the current control mode is kept when the current control mode is the control mode II.

In the above-described engine torque control strategy for a single-motor hybrid vehicle, in the above-described step C, the current engine target torque calculation process is yes (N)_tar-N_now)/t₀When > k, N_out＝kt₀+N_nowWhen (N)_tar-N_now)/t₀When k is less than or equal to k, N_out＝N_tarIn the above formula, N_tarFor the currently available torque demand, N_nowThe target torque t of the engine obtained from the last control period of the whole vehicle controller₀Controlling the period of the whole vehicle controller, wherein k is the current obtained engine target torque increase slope limit value, N_outThe target torque of the engine required to be output at present. The method comprises the steps of subtracting a target engine torque output in the last control period of the whole vehicle controller from a current obtained required torque, dividing the target engine torque output in the last control period of the whole vehicle controller by the duration of the control period to obtain a required torque increase rate, comparing the required torque increase rate with a target engine torque increase slope limit value obtained by table lookup, and obtaining a target engine torque increase amount by multiplying the target engine torque increase slope limit value by the control period of the whole vehicle controller and adding the target engine torque output in the control period when the required torque increase rate is large, wherein the target engine torque increase slope limit value by the control period of the whole vehicle controller. At a demanded torque increase rate of less thanThe engine target torque that is output in accordance with the current required torque as the present control period at the time of being equal to the engine target torque increase slope limit, that is, the current engine target torque.

In the above-described engine torque control strategy for a single-motor hybrid vehicle, in step D, the motor assist torque is (the currently obtained required torque — the currently obtained actual engine torque) × the currently obtained engine-gear-corresponding gear ratio/the currently obtained motor-gear-corresponding gear ratio. And subtracting the currently acquired actual torque of the engine from the currently acquired required torque, and multiplying the currently acquired actual torque of the engine by the ratio of the corresponding transmission ratio of the engine gear to the corresponding transmission ratio of the currently acquired motor gear to obtain the motor assisting torque. The accurate motor power-assisted torque is obtained through the formula, so that accurate power assistance is performed, and the response speed of the required torque is met.

A torque control system of an engine of a single-motor hybrid vehicle comprises a vehicle control unit, wherein a control mode of the engine torque is arranged in the vehicle control unit, the control mode comprises a first control mode with a slope limit table I and a second control mode with a slope limit table II, the vehicle control unit is connected with an engine controller for sending the engine state and the actual engine torque, the target torque increase slope limit value obtained by checking the slope limit table I with the same actual engine torque is smaller than the target torque increase slope limit value obtained by checking the slope limit table II, the vehicle control unit is also connected with a motor controller, a gearbox controller, an accelerator opening sensor and a vehicle speed sensor, the vehicle control unit obtains the required torque through the accelerator opening sensor and the vehicle speed sensor, and obtains the engine gear information and the motor gear information through the gearbox controller, the method comprises the steps that when an engine runs and the current required torque is larger than the target torque of the engine obtained in the last control period of a vehicle controller, the vehicle controller enters a control mode, the vehicle controller obtains the target torque increase slope limit value of the engine through the current obtained actual torque of the engine by looking up a slope limit value table I or a slope limit value table II, the current target torque of the engine is obtained according to the value and the current required torque and is sent to the engine controller, and the vehicle controller obtains the current motor power-assisted torque according to the current actual torque of the engine, the required torque, the engine gear and the motor gear and sends the current motor power-assisted torque.

In the single-motor hybrid vehicle engine torque control system, the whole vehicle controller is used for controlling and calculating the engine torque, the whole vehicle controller is used for respectively obtaining the opening degree of an accelerator pedal and the vehicle speed through a signal sent by an accelerator opening degree sensor and a signal sent by a vehicle speed sensor and checking a driver torque pedal analysis table (the table is the prior art) to obtain the required torque, the whole vehicle controller is used for controlling and calculating the engine torque, a slope limit value table is used for controlling the target torque increase rate of the engine, the target torque increase slope limit value of the engine obtained by checking a slope limit value table I under the same actual torque of the engine is smaller than the target torque increase slope limit value of the engine obtained by checking a slope limit value table II, so that when other calculated variables are the same and the current required torque is larger than the target torque of the engine obtained by the last control period, the target engine torque calculated by the target engine torque increase slope limit value obtained by looking up the slope limit value table I is smaller than the target engine torque calculated by the target engine torque increase slope limit value obtained by looking up the slope limit value table II, namely the rising rate of the target engine torque calculated by looking up the slope limit value table I is smaller, the target engine torque rises more stably, the accurate control of the engine torque is facilitated, and meanwhile, the fuel consumption rate is lower.

After the control mode is entered, whether the control mode is entered into the first control mode or the second control mode, the current engine target torque is calculated, namely the engine target torque of the whole vehicle controller in the control cycle, because the engine target torque is calculated by the engine target torque increase slope limit value and the current required torque, the calculated engine target torque also changes along with the change of the obtained actual engine torque and the change of the required torque, the engine target torque also increases along with the increase of the required torque when the required torque increases, the actual engine torque increases along with the increase of the engine target torque, namely, the actual engine torque changes along with the change of the required engine torque in the control mode. The vehicle control unit sends the target torque of the engine to the engine controller, and the engine controller takes the currently received target torque of the engine as a torque control target of the engine, so that the actual torque of the engine is changed along with the change of the target torque of the engine. And the motor power-assisted torque is also calculated, and the motor also responds to the current torque required by the driver, so that the response speed of the required torque to the vehicle is ensured. Therefore, after the torque control strategy enters the control mode, when the required torque is increased, the motor outputs the motor power-assisted torque for assisting, the actual torque of the engine is gradually increased to meet the increase of the required torque, the motor does not need to supplement the increase of the total required torque independently, and the power consumption of the motor assistance is greatly reduced. Therefore, the direct-drive proportion of the vehicle power assembly is increased, energy loss is reduced, power consumption of motor assistance is greatly reduced, energy consumption of power battery supplement is reduced, fuel consumption is low, and fuel economy of the power assembly is high while the torque demand response speed of the vehicle is guaranteed.

In the single-motor hybrid electric vehicle engine torque control system, the vehicle control unit obtains the opening degree of the accelerator pedal by sending a signal by the accelerator opening degree sensor and calculates the change rate of the accelerator pedal according to the opening degree of the accelerator pedal, the vehicle control unit obtains the peak power output by the motor by the signal sent by the motor controller, the vehicle control unit is connected with a battery manager, and the vehicle control unit obtains the electric quantity and the peak discharge power of the power battery by the battery manager. And selecting to enter a first control mode or a second control mode by judging the change rate of the accelerator pedal, the output peak power of the motor, the electric quantity of the power battery and the discharge peak power of the power battery.

In the engine torque control system of the single-motor hybrid electric vehicle, the input end of the vehicle controller is further connected with an accelerator pedal full-accelerator switch which is closed when an accelerator pedal is fully stepped. After receiving the closing signal of the full accelerator switch of the accelerator pedal, the accelerator pedal is indicated to be completely stepped on and then continues to be deeply stepped on, the requirement of the driver on the response speed of the required torque is indicated to be very high, the current control mode is switched to the control mode II at the moment, and the current control mode is kept when the current control mode is the control mode II.

Compared with the prior art, the engine torque control strategy and the engine torque control system of the single-motor hybrid electric vehicle have the advantages that:

1. according to the invention, the direct-drive proportion of the vehicle power assembly is increased, the energy loss is reduced, and the power consumption of the motor power is greatly reduced, so that the energy consumption supplemented to a power battery is reduced, the fuel consumption is low, and the fuel economy of the power assembly is high while the torque response speed required by the vehicle is ensured.

2. In the control mode I of the invention, the slope limit value table I takes the lowest fuel consumption rate of the engine as a table preparation standard to obtain the lowest target torque increase slope limit value of the engine with the fuel consumption rate under different actual torques of the engine, and then the calculated target torque of the engine is the target torque of the engine with the lowest fuel consumption, so that the fuel consumption rate can be kept at a lower level when the torque of the engine is increased, namely, the low fuel consumption rate when the torque of the engine is increased can be ensured, the power consumption of the motor for assisting power is greatly reduced, and the fuel economy of the power assembly is further improved.

Drawings

FIG. 1 is a schematic diagram of the main flow of the strategy in the present invention.

Fig. 2 is a schematic diagram of the system connection structure of the present invention.

FIG. 3 is a graph illustrating engine torque variation according to a first embodiment of the present invention.

In the figure, 1, a vehicle control unit; 2. an engine controller; 3. a motor controller; 4. a transmission controller; 5. an accelerator opening sensor; 6. a vehicle speed sensor; 7. a battery manager; 8. and an accelerator pedal full accelerator switch.

Detailed Description

The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described with reference to the drawings, but the present invention is not limited to these embodiments.

The first embodiment is as follows:

as shown in fig. 1 and 2, a single motor hybrid vehicle engine torque control strategy includes the steps of:

step A, setting a control mode: the control mode of the engine torque is preset by the vehicle control unit 1, a slope limit table is arranged in the control mode, the control mode comprises a first control mode with a first slope limit table and a second control mode with a second slope limit table, the target torque increase slope limit value of the engine is obtained by checking the corresponding slope limit table according to the actual torque of the engine in the control mode, and the target torque increase slope limit value of the engine obtained by checking the first slope limit table under the same actual torque of the engine is smaller than the target torque increase slope limit value of the engine obtained by checking the second slope limit table. The slope limit table I is provided with a plurality of different engine actual torques, two adjacent engine actual torques form an engine actual torque range, each engine actual torque obtains an engine target torque increase slope limit value with the lowest corresponding fuel consumption rate through a fuel consumption rate experiment, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to each engine actual torque is placed into the slope limit table I, the engine actual torque range of the currently obtained engine actual torque in the slope limit table I is determined according to the size of the currently obtained engine actual torque when the slope limit table is inquired, and the engine target torque increase slope limit value corresponding to the currently obtained engine actual torque is obtained according to an interpolation algorithm. The method does not need to fill the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to all the actual torques of the engine in the slope limit value table, thereby reducing the difficulty of making the table, and simultaneously finding the corresponding engine target torque increase slope limit value with low fuel consumption of the engine through different actual torques of the engine.

In this embodiment, the first slope limit table (which is a one-dimensional table) is prepared as follows: and selecting a plurality of engine actual torques as the engine actual torques in the slope limit value table I, wherein the engine actual torques are used as actual torque reference values, the number and the size of the actual torque reference values can be calibrated, and the actual torque reference values are preferably 0, 20, 40, 60, 80, 100, 150, 200, 250 and 300, and the unit is Nm (Newton meters). And respectively obtaining an engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to the actual torque of the engine through a fuel consumption rate experiment, mounting the engine on an engine experiment bench, connecting an oil supply device of the oil consumption meter and a dynamometer with high precision and sensitivity, starting the experiment, determining an actual torque object of the engine for the experiment, and specifically explaining the actual torque object by taking 40Nm as an example. The initial required torque is recorded as a, the rotating speed is recorded as b, the final required torque is recorded as c, the target torque increase slope limit value of the engine is recorded as x, when the actual torque object of the engine is 40Nm, 20Nm is obtained by subtracting 20Nm from 40Nm, 60Nm is obtained by adding 20Nm to 40Nm, the rotating speed b is set as 1500rpm, and x is selected as the target torque increase slope limit value of the engine in the current experiment.

After the engine is started, the initially required torque a (20Nm) and the rotation speed b (1500rpm) are transmitted to the engine to operate the torque and the rotation speed received by the engine, and after a steady state t1 s (preferably 5 at t 1) is maintained, the engine torque is controlled at x 10Nm/s to increase the engine torque at a rate of 10Nm/s, and after the engine torque reaches the finally required torque c (60Nm), the engine torque is positioned at a steady state t2 s (preferably 7 seconds at t 2). The engine torque change is shown in fig. 3, in which the abscissa is time in seconds, the ordinate is engine torque in Nm, and then the engine torque is reduced to the initially required torque a (20Nm) by repeating the above operations a plurality of times, i.e., the initially required torque a is 20Nm, the rotation speed b is 1500rpm, and the finally required torque c is 60Nm, x is 10Nm/s, and the fuel consumption rate corresponding to the engine is calculated after each experiment, in the process of selecting the engine state from t3s (preferably t3 is 1) before the signal change (i.e., before the engine torque rises) to t4s (preferably t4 is 1) after the steady state of the engine torque change as the basis of calculating the fuel consumption rate, the actual engine torque is 6s at 40Nm, and the engine torque, the engine, The engine fuel consumption rate of the experiment is obtained by substituting the corresponding numerical value into the formula.

Because a plurality of experiments are carried out under the same conditions of a, b, c and x, the engine fuel consumption rate of each experiment is calculated and then averaged, and the engine fuel consumption rates under the conditions of a, b, c and x at present can be obtained. And then replacing a plurality of values of x to carry out the above experimental calculation operation, calculating the engine fuel consumption rate corresponding to each x under the same conditions of a, b and c, and selecting the value of x corresponding to the minimum engine fuel consumption rate as the lowest engine target torque increase slope limit value under the current conditions of a, b and c, namely, the value of x is used as the engine target torque increase slope limit value corresponding to the actual engine torque 40 Nm. The number and value of x can be calibrated, and x is 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10 and 5 in Nm/s in the embodiment.

The above experiment resulted in the lowest engine target torque increase slope limit at which the actual engine torque was 40 Nm. The lowest value of the target torque increase slope limit for the engine obtained from the engine actual torques 60Nm, 80Nm, 100Nm, 150Nm, 200Nm, 250Nm experiments is the same as the experiment performed when the engine actual torque is 40Nm, where a is the actual engine torque minus 20Nm, b is 1500rpm, c is the actual engine torque plus 20Nm, e.g., 60Nm, a is 40Nm, and c is 80 Nm. When the actual engine torque is 20Nm, the value of a is 10Nm by subtracting 10Nm from the actual engine torque, the value of b is 1500rpm, and the value of c is 30Nm by adding 10Nm to the actual engine torque. The engine target torque increase slope limit obtained at an engine actual torque of 20Nm is also taken as the engine target torque increase slope limit at an engine actual torque of 0Nm, and the engine target torque increase slope limit obtained at an engine actual torque of 250Nm is also taken as the engine target torque increase slope limit at an engine actual torque of 300 Nm.

The slope limits were prepared as follows:

and the table making mode of the first slope limit value table can also carry out real vehicle calibration to select the engine target torque increase slope limit value corresponding to the selected engine actual torque according to experience.

In this embodiment, the slope limit table two (which is a one-dimensional table) is prepared as follows:

when the slope limit table II is manufactured, the target torque increase slope limit value of the engine mainly considers that the response speed of the engine is high. And selecting a plurality of engine actual torques as the engine actual torques in the slope limit value table II, wherein the engine actual torques are used as actual torque reference values, the number and the size of the actual torque reference values can be calibrated, and the actual torque reference values are preferably 0, 20, 40, 60, 80, 100, 150, 200, 250 and 300, and the unit is Nm (Newton meters). The method comprises the steps of taking an engine target torque increase slope limit value at the fastest response speed of an engine as a basic value (the prior art), adopting the basic value to form a slope limit value table II under each actual torque reference value, then carrying out actual vehicle calibration to modify the basic value in the slope limit value table II, and recording signals of acceleration of the whole vehicle, an accelerator pedal signal, vehicle speed, engine target torque, actual engine torque, actual motor torque and the like through inca software. Setting a designated vehicle speed (such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170 and 180), setting a maximum accelerator pedal opening signal (such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%), accelerating the vehicle to the designated vehicle speed and then driving at a constant speed, stepping on an accelerator pedal for acceleration, wherein the accelerator pedal opening signal does not exceed a set value during vehicle acceleration, experiencing vehicle acceleration feeling during acceleration, whether the vehicle is unsmooth, jerked or slow in dynamic response, looking up data recorded by inca software through mda software, finding an actual engine torque corresponding to the position where acceleration fluctuates or changes, and judging whether the acceleration fluctuates or changes due to the unsmooth jerked or slow in acceleration or the acceleration changes due to the slow in acceleration data at the position where acceleration fluctuates or changes, and if the acceleration is caused by the uneven burst, reducing the engine target torque increase slope limit value corresponding to the corresponding engine actual torque, and reducing the engine target torque increase slope limit value corresponding to four engine actual torques adjacent to the engine actual torque in a slope limit table II, wherein if the engine actual torque corresponding to the found position where the acceleration fluctuates or changes is 30Nm, reducing the engine target torque increase slope limit values corresponding to 0Nm, 20Nm, 40Nm and 60Nm in the slope limit table II. If the power response is slow, the obtained engine actual torque is adjusted to be larger corresponding to the engine target torque increase slope limit value, and the engine target torque increase slope limit value reference value corresponding to four engine actual torques adjacent to the engine actual torque in the slope limit value table two is adjusted to be larger. The actual vehicle calibration is performed for several times to determine the value in the slope limit table two, which in this embodiment is:

step B, entering a control mode: the vehicle control unit 1 enters a control mode when the engine runs and the current required torque is larger than the target torque of the engine obtained in the last control cycle of the vehicle control unit 1, and then the vehicle control unit 1 enters a control mode I when judging that the change rate of the accelerator pedal meets the change condition and the motor has large power-assisting capacity, and enters a control mode II when judging that the change rate of the accelerator pedal does not meet the condition of the control mode I. The vehicle control unit 1 calculates the change rate of the accelerator pedal, and judges that the change rate of the accelerator pedal meets a change condition when the change rate of the accelerator pedal is less than or equal to a change threshold value, otherwise, the vehicle control unit enters a control mode II; the vehicle control unit 1 acquires the electric quantity of a power battery, and enters a control mode II when the electric quantity of the power battery is judged to be smaller than or equal to an electric quantity threshold value, the vehicle control unit 1 acquires the discharge peak power of the power battery, and enters the mode II when the discharge peak power is judged to be smaller than or equal to a discharge threshold value, the vehicle control unit 1 acquires the output peak power of the motor, and enters the control mode II when the output peak power of the motor is smaller than or equal to the peak threshold value, and the vehicle control unit 1 judges that the motor has large power assisting capability when the electric quantity of the power battery is larger than the electric quantity threshold value, the discharge peak power is. The target torque of the engine obtained in the last control cycle of the vehicle control unit 1 can be obtained by the vehicle control unit 1 by retrieving data in its own memory module, which is the prior art.

When the change rate of the accelerator pedal is higher than the change threshold, the current torque demand change rate is larger, a slope limit table which enables the rising rate of the target torque of the engine to be smaller needs to consume larger electric quantity for assisting, and the motor assisting torque is difficult to compensate the difference part of the actual torque and the demand torque of the engine due to too fast electric quantity consumption in the motor assisting process, so that the response speed is reduced. When the electric quantity of the power battery is smaller than or equal to an electric quantity threshold value, the output peak power of the motor is smaller than or equal to a discharge peak value threshold value, or the discharge peak power of the power battery is smaller than or equal to a discharge threshold value, the motor power-assisted capacity is required to be reduced rapidly by increasing the torque rise rate of the engine, so that the response speed is ensured, when the change rate of an accelerator pedal is smaller than or equal to a change threshold value, the electric quantity of the power battery is larger than an electric quantity threshold value, the discharge peak power of the motor is larger than a discharge peak value threshold value, and the change rate of the accelerator pedal meets a change condition, and the motor has large power-assisted capacity, so that a first control mode is entered, and the target. The difference between entering the first control mode and entering the second control mode is that the slope limit table is different.

The variation threshold is chosen in the range of 20 °/s to 100 °/s, preferably 40 °/s. The electric quantity threshold value is selected to be in a range of 20% to 40% of rated electric quantity of the power battery, and is preferably 30% of the electric quantity threshold value. The discharge threshold is selected in the range of 20kW to 60kW, with a preferred discharge threshold of 50 kW. The peak threshold is selected in the range of 20kW to 60kW, preferably 60 kW.

And when the current required torque is larger than the engine target torque obtained in the last control period of the vehicle control unit 1, directly entering a control mode II after receiving a closing signal of the accelerator pedal full accelerator switch 8. After receiving the closing signal of the accelerator pedal full accelerator switch 8, the accelerator pedal is indicated to be fully stepped on and then continues to be deeply stepped on, at this time, the requirement of the driver on the response speed of the required torque is indicated to be very high, at this time, the current control mode is switched to the control mode II for the first time, and the current control mode is kept when the current control mode is the control mode II.

Step C, obtaining the current target torque: after entering the control mode, the vehicle control unit 1 obtains an engine target torque increase slope limit value through the currently obtained actual torque of the engine, calculates the current engine target torque through the engine target torque increase slope limit value and the current required torque, and sends the calculated current engine target torque to the engine control unit 2. The target torque of the engine is required to be calculated whether the engine enters the first control mode or the second control mode, but the slope limit table for checking the actual torque of the engine obtained currently is different during calculation, the table for checking the slope limit table one and the table for checking the slope limit table two are the same, and the table for checking the slope limit table one is described below. After the vehicle controller 1 obtains the actual engine torque, determining that the actual engine torque is in an actual engine torque range in a slope limit table one according to the magnitude of the current actual engine torque, if the current actual engine torque is 30Nm, the actual engine torque is in an actual engine torque range of 20Nm to 40Nm in the slope limit table one, and then obtaining an engine target torque increase slope limit corresponding to the current actual engine torque according to an interpolation algorithm, wherein the interpolation algorithm is Kx ═ K2-K1)/(N2-N1) × (Nx-N1) + K1, where N1 is a smaller actual torque reference value in the actual engine torque range corresponding to the current actual engine torque in the slope limit table one, K1 is an engine target torque increase slope limit corresponding to the actual torque reference value, and N2 is a larger actual torque reference value in the actual engine torque range corresponding to the current actual engine torque in the slope limit table one, where K2 is the corresponding engine target torque increase slope limit value under the actual torque reference value, Nx is the currently acquired engine actual torque, Kx is the corresponding engine target torque increase slope limit value under the currently acquired engine actual torque, and when the previous engine actual torque is 30Nm, Nx is equal to 30Nm, N1 is equal to 20Nm, N2 is equal to 40Nm, K1 is equal to 300Nm/s, and K2 is equal to 200Nm/s, the above formula is substituted to obtain Kx ═ 200 Nm/300)/(40-20) × (30-20) +300, so Kx is equal to 250Nm/s, that is, the engine target torque increase slope limit value of the lowest fuel consumption rate corresponding to the current engine actual torque being 30Nm is 250 Nm/s. And if the currently acquired actual engine torque is just recorded in the slope limit table, selecting the recorded value as the current target engine torque increase slope limit value, wherein if the currently acquired actual engine torque is 40Nm, the current target engine torque increase slope limit value is 200 Nm/s.

The current engine target torque calculation process is when (N)_tar-N_now)/t₀When > k, N_out＝kt₀+N_nowWhen (N)_tar-N_now)/t₀When k is less than or equal to k, N_out＝N_tarIn the above formula, N_tarFor the currently available torque demand, N_nowTarget torque t of engine obtained from last control cycle of vehicle controller 1₀For the control period of the vehicle control unit 1, k is the current target torque increase slope limit value of the engine (k is the same as Kx), and N is_outThe target torque of the engine required to be output at present. Subtracting the target engine torque output by the last control period of the vehicle controller 1 from the current required torque, dividing the target engine torque by the control period duration to obtain a required torque increase rate, comparing the required torque increase rate with a target engine torque increase slope limit value obtained by table lookup, and outputting the target engine torque by the vehicle controller 1 when the required torque increase rate is large (namely outputting the target engine torque by the control period)The engine target torque) is equal to the engine target torque increase slope limit value multiplied by the control period of the vehicle controller 1 plus the engine target torque output in one control period, and the engine target torque increase slope limit value multiplied by the control period of the vehicle controller 1 obtains the required engine torque increase. The engine target torque that is output in accordance with the current required torque as the present control period when the required torque increase rate is equal to or less than the engine target torque increase slope limit value, that is, the current engine target torque. The control cycle of the vehicle control unit 1 is the cycle of software running calculation in the vehicle control unit 1, and the control cycle duration is 10 ms.

The vehicle control unit 1 gives the calculated engine target torque to the engine controller 2, and the engine controller 2 takes the currently received engine target torque as a torque control target of the engine, and the engine performs torque change with the control of the engine controller 2, and the actual torque of the engine increases as the engine target torque increases.

And searching and obtaining a corresponding engine target torque increase slope limit value with the lowest fuel consumption rate according to the currently obtained actual torque of the engine, and then calculating the engine target torque to be the target torque of the engine with the lowest fuel consumption, so that the fuel consumption rate is kept at a lower level when the engine torque is increased.

D. Calculating the torque of the motor: the vehicle control unit 1 obtains a current motor power-assisted torque according to the currently obtained actual torque of the engine, the required torque, the engine gear and the motor gear, the vehicle control unit 1 sends the current motor power-assisted torque to the motor controller 3, and the motor works with the obtained motor power-assisted torque. The motor assist torque is (the currently obtained required torque — the currently obtained actual torque of the engine) multiplied by the currently obtained transmission ratio corresponding to the engine gear/the currently obtained transmission ratio corresponding to the motor gear. The accurate motor power-assisted torque is obtained through the formula, so that accurate power assistance is performed, and the response speed of the required torque is met. The motor controller 3 also controls the motor to output the motor assist torque when the engine controller 2 controls the engine torque to change, so that the two are added to meet the response speed of the current required torque.

In the engine torque control strategy of the single-motor hybrid vehicle, when the engine runs and the current required torque is larger than the target torque of the engine obtained in the last control cycle of the vehicle control unit 1, the current engine torque cannot meet the requirement of the current driving torque of a driver, and then the vehicle control method enters a control mode. The vehicle control unit 1 can retrieve the target engine torque obtained in the last control cycle from the memory module of the vehicle control unit. After the engine enters the control mode, the engine target torque increase slope limit value obtained by checking the slope limit value table I under the same actual engine torque is smaller than the engine target torque increase slope limit value obtained by checking the slope limit value table II, so that when other calculated variables are the same, the engine target torque obtained by calculating the engine target torque increase slope limit value obtained by checking the slope limit value table I is smaller than the engine target torque obtained by calculating the engine target torque increase slope limit value obtained by checking the slope limit value table I, namely the rising rate of the engine target torque calculated by checking the slope limit value table I is smaller, the engine target torque rises more stably, the engine torque is controlled accurately, and meanwhile, the fuel consumption rate is lower.

After the control mode is entered, whether the control mode is entered into the first control mode or the second control mode, the current engine target torque is calculated, namely the engine target torque of the control cycle of the vehicle control unit 1, because the engine target torque is calculated by the engine target torque increase slope limit value and the current required torque, the calculated engine target torque is changed along with the change of the obtained actual engine torque and the change of the required torque, the engine target torque is increased along with the increase of the required torque when the required torque is increased, the actual engine torque is increased along with the increase of the engine target torque, namely, the actual engine torque is changed along with the change of the required engine torque in the control mode, and the actual engine torque is changed along with the change of the engine target torque. The vehicle control unit 1 transmits the calculated engine target torque to the engine controller 2 every time the engine target torque is calculated, and the engine controller 2 takes the currently received engine target torque as a torque control target of the engine. And the motor power-assisted torque is also calculated, and the motor also responds to the current torque required by the driver, so that the response speed of the required torque to the vehicle is ensured. Therefore, after the torque control strategy enters the control mode, when the required torque is increased, the motor outputs the motor power-assisted torque for assisting, the actual torque of the engine is gradually increased to meet the increase of the required torque, the motor does not need to supplement the increase of the total required torque independently, and the power consumption of the motor assistance is greatly reduced. Therefore, the direct-drive proportion of the vehicle power assembly is increased, energy loss is reduced, power consumption of motor assistance is greatly reduced, energy consumption of power battery supplement is reduced, fuel consumption is low, and fuel economy of the power assembly is high while the torque demand response speed of the vehicle is guaranteed. Meanwhile, in the slope limit table I in the control mode I, the slope limit value table I takes the lowest fuel consumption rate of the engine as a table preparation standard to obtain the lowest target torque increase slope limit value of the engine with the fuel consumption rate under different actual torques of the engine, and then the calculated target torque of the engine is the target torque of the engine with the lowest fuel consumption rate, so that the fuel consumption rate can be kept at a lower level when the torque of the engine is increased, namely the low fuel consumption rate when the torque of the engine is increased can be ensured, the power consumption of the motor for assisting power is greatly reduced, and the fuel economy of the power assembly is further improved.

As shown in fig. 1 and fig. 2, the control strategy is applied to an engine torque control system of a single-motor hybrid vehicle, the control system comprises a vehicle control unit 1, a control mode of engine torque is arranged in the vehicle control unit 1, the control mode comprises a first control mode with a slope limit table I and a second control mode with a slope limit table II, the vehicle control unit 1 is connected with an engine controller 2 which sends an engine state and an actual engine torque, and an engine target torque increase slope limit value obtained by checking the slope limit table I with the same actual engine torque is smaller than an engine target torque increase slope limit value obtained by checking the slope limit table II. The vehicle control unit 1 is further connected with a motor controller 3, a gearbox controller 4, an accelerator opening sensor 5 and a vehicle speed sensor 6, the vehicle control unit 1 obtains required torque through the accelerator opening sensor 5 and the vehicle speed sensor 6, and obtains engine gear information and motor gear information through the gearbox controller 4. The vehicle control unit 1 obtains the opening degree of an accelerator pedal through a signal sent by an accelerator opening degree sensor 5, and obtains the vehicle speed through a signal sent by a vehicle speed sensor 6. The current required torque is obtained by looking up a driver torque pedal analysis table according to the opening degree of an accelerator pedal and the vehicle speed, and the description is omitted for the prior art.

The vehicle control unit 1 obtains the opening degree of an accelerator pedal by sending a signal by an accelerator opening degree sensor 5, and the vehicle control unit 1 obtains the change rate of the accelerator pedal by subtracting the opening degree of the accelerator pedal in the last control period from the current obtained opening degree of the accelerator pedal and dividing the control period duration. The vehicle control unit 1 obtains the output peak power of the motor through a signal sent by the motor controller 3, the vehicle control unit 1 is connected with a battery manager 7, and the vehicle control unit 1 obtains the electric quantity and the discharge peak power of the power battery through the battery manager 7. And selecting to enter a first control mode or a second control mode by judging the change rate of the accelerator pedal, the output peak power of the motor, the electric quantity of the power battery and the discharge peak power of the power battery.

The engine controller 2 receives the control signal to control the engine torque to be changed into the function of the engine controller, the engine controller 2 can send the actual engine torque and the state whether the engine is started or not, the motor controller 3 receives the control signal to control the motor torque to be changed into the function of the motor controller, and the motor controller 3 can obtain and transmit the peak power output by the motor to be also used as the function of the motor controller. The transmission controller 4 can obtain engine gear information and motor gear information (such as a transmission ratio corresponding to the engine gear and a transmission ratio corresponding to the motor gear) as its own functions. The battery manager 7 obtains the electric quantity and the discharge peak power of the power battery as the functions of the battery manager. The accelerator opening sensor 5 is a voltage sensor, the change of the accelerator pedal changes the voltage output by the voltage sensor to the vehicle control unit 1, and the corresponding accelerator pedal opening is obtained by checking a preset voltage and accelerator opening table according to the received voltage, which is the prior art. The accelerator opening sensor 5 may be an angle sensor.

The input end of the vehicle control unit 1 is also connected with an accelerator pedal full accelerator switch 8 which is closed when the accelerator pedal is fully stepped. When the current required torque is larger than the actual torque of the engine, the fact that the accelerator pedal is completely stepped on and then continues to be deeply stepped on after the accelerator pedal full accelerator switch 8 is closed is received, the fact that the response speed requirement of a driver on the required torque is high is shown, the current control mode is switched to the second control mode for the first time, and the current control mode is kept when the current control mode is the second control mode.

The vehicle control unit 1 receives an engine state signal sent by the engine controller 2 in real time to judge whether the engine is started to operate and receives and acquires accelerator pedal opening and vehicle speed in real time to obtain the current required torque of a driver, when the engine operates and the current required torque is larger than the target torque of the engine obtained in the last control cycle of the vehicle control unit 1, the vehicle control unit enters a control mode, then judges whether the current electric quantity of a power battery is larger than an electric quantity threshold value, whether the discharge peak power is larger than a discharge threshold value, whether the output peak power of a motor is larger than a peak value threshold value, and whether the accelerator pedal change rate is higher than or equal to a change threshold value, and enters a control mode I when the electric quantity of the power.

After entering the control mode, the corresponding slope limit table is checked according to the current actual torque of the engine obtained by the engine controller 2, the first slope limit table is checked when entering the control mode, and the second slope limit table is checked when entering the control mode. The values of the first slope limit table and the second slope limit table are set as in the torque control strategy described above.

The first slope limit table is similar to the second slope limit table in the same way, and the first slope limit table will be described below. After the actual engine torque is obtained, determining that the actual engine torque is in an actual engine torque range in a slope limit table I according to the magnitude of the current actual engine torque, if the current actual engine torque is 30Nm, the actual engine torque is in an actual engine torque range of 20Nm to 40Nm in the slope limit table I, then obtaining an engine target torque increase slope limit corresponding to the current actual engine torque according to an interpolation algorithm, wherein the interpolation algorithm is Kx ═ K2-K1)/(N2-N1) × (Nx-N1) + K1, N1 is a smaller actual torque reference value in the actual engine torque range corresponding to the current actual engine torque in the slope limit table I, K1 is an engine target torque increase limit corresponding to the boundary value, N2 is a larger actual torque reference value in the actual engine torque range corresponding to the current actual engine torque in the slope limit table I, where K2 is the engine target torque increase slope limit corresponding to the boundary value, Nx is the current engine actual torque, and Kx is the engine target torque increase slope limit corresponding to the current engine actual torque, and when the previous engine actual torque is 30Nm, Nx is equal to 30Nm, N1 is equal to 20Nm, N2 is equal to 40Nm, K1 is equal to 300Nm/s, and K2 is equal to 200Nm/s, the above formula is substituted to obtain Kx ═ 200 and 300)/(40-20) × (30-20) +300, so Kx is equal to 250Nm/s, that is, the engine target torque increase slope limit corresponding to the lowest fuel consumption rate when the current engine actual torque is 30Nm is 250 Nm/s.

Calculating the target torque of the engine to be output in the current control period, wherein the calculation process is as (N)_tar-N_now)/t₀When > k, N_out＝kt₀+N_nowWhen (N)_tar-N_now)/t₀When k is less than or equal to k, N_out＝N_tarIn the above formula, N_tarFor the currently available torque demand, N_nowTarget torque t of engine obtained from last control cycle of vehicle controller 1₀Controlling the period of the whole vehicle controller 1, wherein k is the current obtained engine target torque increase slope limit value, N_outThe target torque of the engine required to be output at present.

The hybrid vehicle controller 1 gives the calculated engine target torque to the engine controller 2, and the engine controller 2 takes the currently received engine target torque as a torque control target of the engine, which is changed with the control torque of the engine controller 2, and the actual torque of the engine is increased as the engine target torque is increased.

The corresponding engine target torque increase slope limit value with the lowest fuel consumption rate is obtained by searching according to the current actual torque of the engine, and then the calculated engine target torque is the target torque of the engine with the lowest fuel consumption rate, so that the fuel consumption rate can be kept at a lower level when the engine torque is increased.

The vehicle control unit 1 obtains a motor assisting torque according to the currently obtained actual torque of the engine, the required torque, the engine gear and the motor gear, and the motor works with the obtained motor assisting torque. The motor assist torque is (the currently obtained required torque — the currently obtained actual torque of the engine) multiplied by the currently obtained transmission ratio corresponding to the engine gear/the currently obtained transmission ratio corresponding to the motor gear. The accurate motor power-assisted torque is obtained through the formula, so that accurate power assistance is performed, and the response speed of the required torque is met. When the engine controller 2 controls the engine torque to change, the motor controller 3 receives a motor power-assisted torque signal sent by the vehicle control unit 1, so that the motor controller 3 also controls the motor to output the motor power-assisted torque, and the motor power-assisted torque are added to meet the response speed of the current required torque.

In the engine torque control system of the single-motor hybrid vehicle, when the required torque is increased, the motor outputs the motor power-assisted torque for assisting, the actual torque of the engine is gradually increased to meet the increment of the required torque, the motor does not need to supplement the increment of all the required torque independently, and the power consumption of the motor assistance is greatly reduced. Therefore, the direct-drive proportion of the vehicle power assembly is increased, energy loss is reduced, power consumption of motor assistance is greatly reduced, energy consumption of power battery supplement is reduced, fuel consumption is low, and fuel economy of the power assembly is high while the torque demand response speed of the vehicle is guaranteed. Meanwhile, in the slope limit table I in the control mode I, the slope limit value table I takes the lowest fuel consumption rate of the engine as a table preparation standard to obtain the lowest target torque increase slope limit value of the engine with the fuel consumption rate under different actual torques of the engine, and then the calculated target torque of the engine is the target torque of the engine with the lowest fuel consumption rate, so that the fuel consumption rate can be kept at a lower level when the torque of the engine is increased, namely the low fuel consumption rate when the torque of the engine is increased can be ensured, the power consumption of the motor for assisting power is greatly reduced, and the fuel economy of the power assembly is further improved.

Example two:

the second embodiment is basically the same as the first embodiment in the strategy and system, and the difference is that: in the step a, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to different actual engine torques is selected as the engine target torque increase slope limit value in the slope limit value table one. The first slope limit table has a plurality of engine target torque increase slope limits, and each engine target torque increase slope limit corresponds to one engine actual torque. The actual torque reference value for the actual torque of the engine is taken for each integer between 0Nm and 300 Nm. And performing a fuel consumption rate experiment on each actual torque reference value to obtain an engine target torque increase slope limit value corresponding to each actual torque reference value, comparing the currently obtained engine actual torque (rounded to an integer when the obtained engine actual torque is an integer with a decimal) with the reference values in the table when the table is searched, and when the comparison is consistent, obtaining the engine target torque increase slope limit value corresponding to the reference value as the current table search result. Through the method, the corresponding engine target torque increase slope limit value with the lowest fuel consumption rate is searched and obtained according to the current actual engine torque, and then the calculated engine target torque is the target torque of the engine with the lowest fuel consumption, so that the fuel consumption rate is kept at a lower level when the actual engine torque is increased.

The specific embodiments described herein are merely illustrative of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Although the terms vehicle control unit 1, engine controller 2, motor controller 3, transmission controller 4, accelerator opening sensor 5, vehicle speed sensor 6, battery manager 7, accelerator pedal full throttle switch 8, etc. are used more herein, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to any additional limitations that may be imposed by the spirit of the present invention.

Claims

1. An engine torque control strategy for a single motor hybrid vehicle, the strategy comprising the steps of:

A. setting a control mode: the method comprises the steps that a control mode of engine torque is preset by a vehicle control unit (1), a slope limit table is arranged in the control mode, the control mode comprises a first control mode with a first slope limit table and a second control mode with a second slope limit table, a target torque increase slope limit value of an engine is obtained by checking the corresponding slope limit table according to actual engine torque in the control mode, and the target torque increase slope limit value of the engine obtained by checking the first slope limit table is smaller than the target torque increase slope limit value of the engine obtained by checking the second slope limit table according to the same actual engine torque;

B. entering a control mode: the method comprises the steps of entering a control mode when an engine runs and the current required torque is larger than the target torque of the engine obtained in the last control cycle of a vehicle control unit (1), and then entering a first control mode when the change rate of an accelerator pedal meets a change condition and a motor has large power-assisting capacity, and entering a second control mode when the change rate of the accelerator pedal does not meet the condition of the first control mode;

C. obtaining the current target torque: after entering a control mode, obtaining an engine target torque increase slope limit value through the currently obtained engine actual torque, calculating through the engine target torque increase slope limit value and the currently required torque to obtain a current engine target torque, and sending the current engine target torque to an engine controller (2), wherein a slope limit table I in a first control mode takes the lowest fuel consumption rate of an engine as a table making standard, the slope limit table I is checked after entering the first control mode to obtain the engine target torque increase slope limit value with the lowest fuel consumption rate under the currently obtained engine actual torque, and the calculated engine target torque is the target torque of the engine with the lowest fuel consumption;

D. calculating the torque of the motor: and obtaining the current motor assisting torque according to the currently obtained actual torque of the engine, the required torque, the engine gear and the motor gear, and sending the current motor assisting torque to the motor controller (3).

2. The one-motor hybrid vehicle engine torque control strategy of claim 1, in step A, a slope limit table I has a plurality of different engine actual torques, two adjacent engine actual torques form an engine actual torque range, the engine target torque increase slope limit value with the lowest fuel consumption rate is obtained by the fuel consumption rate experiment for each engine actual torque, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to each engine actual torque is put into a slope limit value table I, determining the actual torque range of the engine in the first slope limit value table according to the magnitude of the actual torque of the engine obtained currently when inquiring the slope limit value table, and obtaining an engine target torque increase slope limit value corresponding to the currently obtained actual torque of the engine according to an interpolation algorithm.

3. The engine torque control strategy of the single-motor hybrid vehicle according to claim 1, wherein in the step a, the engine target torque increase slope limit value with the lowest fuel consumption rate corresponding to different actual engine torques is selected as the engine target torque increase slope limit value in the slope limit value table one.

4. The engine torque control strategy of the single-motor hybrid vehicle according to claim 1, 2 or 3, characterized in that in the step B, the accelerator pedal change rate is calculated, and when the accelerator pedal change rate is less than or equal to the change threshold value, the accelerator pedal change rate is judged to meet the change condition, otherwise, the control mode II is entered; the method comprises the steps of obtaining the electric quantity of a power battery, entering a control mode II when the electric quantity of the power battery is judged to be smaller than or equal to an electric quantity threshold value, obtaining the discharge peak power of the power battery, entering the control mode II when the discharge peak power is judged to be smaller than or equal to a discharge threshold value, obtaining the output peak power of a motor, entering the control mode II when the output peak power of the motor is smaller than or equal to the peak threshold value, and judging that the motor has large power-assisting capacity when the electric quantity of the power battery is larger than the electric quantity threshold value, the discharge peak power is larger than the discharge threshold.

5. The engine torque control strategy of the single-motor hybrid vehicle according to claim 4, characterized in that the control mode two is directly entered after the current required torque is larger than the engine target torque obtained in the last control cycle of the vehicle controller (1) and the closing signal of the accelerator pedal full accelerator switch (8) is received.

6. The engine torque control strategy for a single-motor hybrid vehicle according to claim 4, wherein in the step C, the current engine target torque calculation process is when (N)_tar-N_now)/t₀When > k, N_out＝kt₀+N_nowWhen (N)_tar-N_now)/t₀When k is less than or equal to k, N_out＝N_tarIn the above formula, N_tarFor the currently available torque demand, N_nowThe target torque t of the engine obtained for the last control period of the whole vehicle controller (1)₀The control period of the whole vehicle controller (1) is large, k is the current obtained engine target torque increase slope limit value, N_outThe target torque of the engine required to be output at present.

7. The engine torque control strategy for a single-motor hybrid vehicle according to claim 6, wherein in the aforementioned step D, the motor assist torque ═ (currently obtained required torque — currently obtained actual torque of the engine) × currently obtained engine-gear corresponding gear ratio/currently obtained motor-gear corresponding gear ratio.

8. A single-motor hybrid vehicle engine torque control system comprises a vehicle controller (1) and is characterized in that a control mode of engine torque is arranged in the vehicle controller (1), the control mode comprises a control mode I with a slope limit table I and a control mode II with a slope limit table II, the vehicle controller (1) is connected with an engine controller (2) for sending an engine state and the actual engine torque, an engine target torque increase slope limit value obtained by checking the slope limit table I with the same actual engine torque is smaller than an engine target torque increase slope limit value obtained by checking the slope limit table II, the vehicle controller (1) is further connected with a motor controller (3), a gearbox controller (4), an accelerator opening sensor (5) and a vehicle speed sensor (6), the vehicle controller (1) obtains required torque through the accelerator opening sensor (5) and the vehicle speed sensor (6), obtaining engine gear information and motor gear information through a gearbox controller (4), entering a control mode when an engine runs and the current required torque is larger than the engine target torque obtained by a last control cycle of a vehicle controller (1), obtaining an engine target torque increase slope limit value through a slope limit value table I or a slope limit value table II of the currently obtained actual torque of the engine by the vehicle controller (1), obtaining the current engine target torque according to the value and the current required torque, sending the current engine target torque to the engine controller (2), obtaining the engine target torque increase slope limit value with the lowest fuel consumption rate of the engine under the currently obtained actual torque of the engine by looking up the slope limit value table I, and obtaining the engine target torque increase slope limit value with the lowest fuel consumption rate under the currently obtained actual torque of the engine, wherein the calculated engine target torque is the target torque of the engine with the lowest fuel consumption, the vehicle control unit (1) obtains current motor power-assisted torque according to the current actual torque of the engine, the required torque, the engine gear and the motor gear and sends the current motor power-assisted torque to the motor controller (3).

9. The engine torque control system of the single-motor hybrid vehicle according to claim 8, wherein the vehicle control unit (1) obtains the opening degree of an accelerator pedal by sending a signal from an accelerator opening degree sensor (5) and calculates the change rate of the accelerator pedal according to the opening degree of the accelerator pedal, the vehicle control unit (1) obtains the peak output power of the motor by sending a signal from the motor control unit (3), the vehicle control unit (1) is connected with a battery manager (7), and the vehicle control unit (1) obtains the electric quantity and the peak discharge power of the power battery by the battery manager (7).

10. The engine torque control system of a single-motor hybrid vehicle according to claim 9, characterized in that an accelerator pedal full accelerator switch (8) that is closed when an accelerator pedal is fully depressed is further connected to an input end of the vehicle control unit (1).