CN110562238A - Automatic starting control method for engine of hybrid electric vehicle - Google Patents

Abstract

The invention discloses a control method for automatic starting of a hybrid electric vehicle engine. S1: when t1<t<t2, the control system does not receive a brake or accelerator signal, and the car is driven by a motor alone; S2: when t2≤t≤t3, the driving The driver steps on the accelerator, and the control system controls the clutch from the open state to the creep point after receiving the signal of the accelerator pedal, and the clutch torque Tc(t) increases to drag the engine to start, and at the same time the control system controls the motor output torque Tm(t) increase, so that the actual torque Ts(t) remains unchanged, and the control system adjusts the engine speed to the starting speed v _q ; S3: when t3<t≤t4, the clutch is from creep point to closed, and the actual torque Ts(t) of the vehicle remains unchanged, the control system issues an instruction to adjust the engine speed at the same time, so that the growth rate of the engine speed is consistent with the growth rate of the vehicle speed. The hybrid vehicle of the present invention completes the automatic starting control of the engine, and the starting process is smooth and fast.

Description

Hybrid electric vehicle engine automatic start control method

technical field

The invention belongs to the technical field of electric and hybrid vehicles, in particular to a method for automatically starting a hybrid vehicle engine.

Background technique

Hybrid vehicles are driven by engines and/or motors, and are distinguished by different numerical codes according to the different positions of the drive motors in the hybrid power transmission system, which are respectively P0, P1, P2, P3, and P4 configuration hybrid power systems , the motors of each configuration are P0 motor, P1 motor, P2 motor, P3 motor and P4 motor. The P2 motor is placed before the gearbox input shaft, after the clutch connected to the engine, and the P3 motor is placed after the gearbox output shaft. The mode in which the P2 motor and the engine jointly drive the vehicle is the P2 hybrid mode, and the mode in which the P3 motor and the engine jointly drive the vehicle is the P3 hybrid mode.

The current driving logic of hybrid vehicles is: when the driver's demand torque is greater than the maximum torque that the motor can provide, the engine needs to participate, and the engine or the engine and the motor share the vehicle torque. However, car driving is a continuous process, and the driver cannot subjectively and accurately judge when to start the engine, so it is necessary to realize the automatic start of the engine during driving. In addition, due to the requirements for driving comfort, the starting process of the engine should be smooth and free from stagnation. The existing engine automatically starts for a long time and is not smooth, and there is an obvious power interruption during driving, which affects the overall acceleration performance, and the power delay time is relatively long.

Contents of the invention

Aiming at the above-mentioned problems in the prior art, the present invention provides a method for controlling the automatic start of the engine of a hybrid electric vehicle. The hybrid vehicle can complete the automatic start control of the engine when it is driven by pure electricity at a low speed or when it is stopped, and the starting process is stable, improving the efficiency of the engine. The comfort of the driver is improved; the control system distributes the engine demand torque and the motor demand torque according to the driver demand torque, so that the motor and engine operate in the high-efficiency zone.

In order to achieve the above object, the technical solution adopted in the present invention is:

Hybrid vehicle engine automatic start control method, assuming any time is t, the engine output torque at time t is Te(t), the motor output torque is Tm(t), the actual torque is Ts(t), the clutch torque Tc(t ), wherein, the actual torque Ts(t) refers to the torque required to maintain the running of the car at t moment, and the engine automatic start control includes the following steps:

S1: When t1<t<t2, the control system does not receive the brake or accelerator signal, the car is driven by the motor alone, the control system controls the output torque of the motor to increase as Tm(t), the speed of the car rises, and the maximum speed rises to the set creep Driving speed, the output torque of the motor is Tm(t) and the maximum rises to the creep demand torque r;

S2: When t2≤t≤t3, the driver steps on the accelerator, the control system controls the clutch from the open state to the creep point after receiving the signal of the accelerator stepping on, and the clutch torque Tc(t) increases to drag the engine to start, and at the same time The control system controls the output torque Tm(t) of the motor to increase so that the actual torque Ts(t) remains unchanged, and the control system issues an instruction to adjust the engine speed to adjust the engine speed to the starting speed v _q ;

S3: When t3<t≤t4, the clutch is closed from the creep point, the control system controls the output torque of the motor to decrease as Tm(t), the output torque of the engine increases as Te(t), and the actual torque Ts(t) of the vehicle remains constant change, the control system issues an instruction to adjust the engine speed at the same time, so that the growth rate of the engine speed v _f (t) is consistent with the growth rate of the vehicle speed v _f (t), and the engine start is completed.

In step S1, the vehicle speed remains unchanged after reaching the set creep speed, the motor output torque Tm(t) remains unchanged after reaching the creep demand torque r, and the motor output torque Tm(t) reaches the set creep speed when the vehicle speed reaches the set creep speed. Creep demand torque r.

In step S1, the clutch is kept open.

Before time t1, the working condition of the car is that when the vehicle speed is very low or in the parking state, the driver steps on the brake and releases the accelerator, the engine is in the stop state, and the clutch is in the open state.

At time t1, the driver releases the brake, and the control system controls the output torque Tm(t) of the motor to rise and the vehicle speed to rise after receiving the signal of brake cancellation.

In S1, Ts(t)=Tm(t); Te(t)=Tc(t)=0.

In S2, v _q = v _in +x, where:

x is an experience correction value;

v _in is the rotational speed of the gearbox input shaft at the time of anti-drag;

The definition of anti-dragging moment: when the control system detects for the first time that the engine speed v _f (t) keeps increasing within 20ms.

In S2, the following parameters are satisfied:

Ts(t)+Tc(t)=Tm(t),

Ts(t)≤r, Tc(t2)=0,

Tc(t3)=Te(t3)=a,

where a is the engine cranking torque used to start the engine.

In S2, the driver steps on the accelerator at time t2, and the control system controls the clutch to start closing at time t2' after receiving the accelerator signal, wherein, t2<t2'<t3, at time t3, the clutch is closed to the creep point position, and the engine is driven by the clutch Anti-drag start.

In S3, Ts(t)=Tm(t)+Te(t)=Ts(t2).

When the car starts successfully and runs normally, the engine output torque Te(t) reaches the engine demand torque b, and the motor output torque Tm(t) reaches the motor demand torque d, where the engine demand torque b and the motor demand torque d refer to the throttle signal holding Under the same circumstances, the torque borne by the engine and the torque borne by the motor when the car is running stably.

The engine demand torque b and the electric motor demand torque d are the values distributed by the control system according to the driver demand torque transmitted by the throttle signal.

The car's gearbox cannot switch gears during automatic engine start.

Compared with the prior art, the beneficial effect of the present invention is: the hybrid vehicle can complete the automatic start control of the engine at low speed or in the parking situation when pure electric driving; when the torque demand transmitted by the throttle is greater than the maximum torque that the actual motor can provide , the control system of the car automatically starts the engine; the engine is driven by the clutch to start, and the clutch is driven by the motor; the speed of the input shaft of the gearbox is calculated during the clutch closing process, so that the engine speed is adjusted to match the input speed of the gearbox during the clutch closing process. The starting speed related to the shaft speed can speed up the clutch closing process and shorten the power interruption time. At the same time, the actual torque of the car remains unchanged during the starting process, which meets the needs of the car for smooth starting, optimizes the smoothness of automatic start and stop power, and takes into account the power; the engine After a successful start, the control system distributes the engine demand torque and motor demand torque according to the driver demand torque, so that the motor and engine run in the high-efficiency zone.

Description of drawings

Figure 1 is a schematic diagram of an embodiment of the present invention.

Detailed ways

The method for controlling the automatic start-up of the engine of the hybrid electric vehicle provided by the present invention will be further described in detail and completely below in conjunction with the embodiments. The embodiments described below are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

The hybrid electric vehicle engine automatic starting control method is used in the hybrid electric vehicle, and the motor is used to start the engine. After starting, the engine participates in driving the vehicle.

The car includes an engine, a motor, a clutch, a gear transmission mechanism, a mode transmission mechanism, a gearbox input shaft and a gearbox output shaft, the engine is connected to the gearbox input shaft through the clutch, and the gearbox output shaft is connected to the differential of the car The gearbox input shaft and the gearbox output shaft are connected through a gear transmission mechanism, that is, the engine is sequentially driven to the differential through the clutch, the gearbox input shaft, the gear transmission mechanism and the gearbox output shaft. The mode transmission mechanism includes N gear, P2 gear and P3 gear. The P2 gear is respectively connected to the motor and the input shaft of the gearbox to form a P2 motor. The P3 gear is connected to the motor and the gearbox output shaft to make the motor to form a P3 motor, namely , the motor sequentially transmits the drive to the differential through the P2 gear, the gearbox input shaft, the gear transmission mechanism and the gearbox output shaft; or the motor sequentially transmits the drive to the differential through the P3 gear and the gearbox output shaft. When the motor is connected to the N gear, the drive of the motor cannot be transmitted to the gearbox input shaft and the gearbox output shaft.

The hybrid vehicle can be driven by the engine and/or the motor. When it is only driven by the engine, it is a traditional pure oil mode. The engine transmits the drive to the output shaft of the gearbox through a gear transmission mechanism. Switched forward gear and a reverse gear, this is common knowledge well known to those skilled in the art, and will not repeat them here. In the pure electric mode driven by the motor, the motor directly drives the car, the clutch is opened, and the engine does not work. The pure electric mode includes P2 pure electric mode and P3 pure electric mode. In the P2 pure electric mode, it is driven by the P2 motor, and the P2 motor transmits the drive to the output shaft through the gear transmission mechanism; in the P3 pure electric mode, the P3 motor is connected and driven Output shaft. The hybrid driving mode driven by the engine and the motor at the same time includes the P3 hybrid mode and the P2 hybrid mode. The P3 hybrid mode is the working mode in which the engine and the P3 motor drive the car together, and the P2 hybrid mode is the engine and the P2 motor drive the car together. working mode.

There is a control system on the car, and the control system includes a controller HTCU. When the accelerator signal or brake signal of the car changes, the HTCU controls the engine and/or the motor and/or the clutch according to the received data signal.

For the hybrid vehicle, when the driver steps on the accelerator and the control system judges that the required torque transmitted by the accelerator is greater than the maximum torque that the current actual motor can provide, the control system controls the engine to start automatically. The specific process is as follows:

Let any moment be t, the engine output torque at time t is Te(t), the motor output torque is Tm(t), the actual torque is Ts(t), the clutch torque is Tc(t), the actual vehicle speed v(t) , engine speed v _f (t). Wherein, the actual torque Ts(t) is the actual torque of the vehicle at time t, in other words, the actual torque Ts(t) refers to the torque required to maintain the running of the vehicle at time t. The actual torque Ts(t) is provided by the electric machine and/or the engine. The automatic engine start control method includes the steps of:

Step S1: When t1<t<t2, the control system does not receive the brake or accelerator signal, the car is driven by the motor alone, the clutch remains open, the control system controls the output torque of the motor so that Tm(t) rises, the speed of the car rises, and the speed is the highest Rising to the set creep speed, the output torque of the motor is Tm(t) and the maximum rises to the creep demand torque r.

Before time t1, the working condition of the car is that when the vehicle speed is very low or in the parking state, the driver steps on the brake and releases the accelerator, the engine is in the stop state, and the clutch is in the open state.

At time t1, the driver releases the brake, and the control system controls the output torque of the motor to increase from Tm(t1) after receiving the signal of brake cancellation. Preferably, Tm(t1)=3Nm, the vehicle speed increases, and the control vehicle speed rises to the highest In order to set the creeping speed, the setting creeping speed is set according to the specific vehicle, and in this application, 14km/h～16km/h is taken. After the creeping vehicle speed is known, the creeping required torque r can be obtained. The vehicle speed is related to the motor torque. The relationship between the vehicle speed and the motor torque is well known to those skilled in the art, and will not be repeated here.

In this step, the brake is released, the accelerator is not stepped on, the car is working in creep mode, the motor output torque Tm(t) gradually increases, and the car speed gradually increases. When the car speed reaches the set creep speed, the motor output torque Tm(t) t) stops increasing and remains unchanged. At this time, the motor output torque Tm(t) is the creep demand torque r, and then the vehicle speed remains unchanged. Among them, r is a constant. For vehicles of different models and displacements, the value of the creep demand torque r is different. For the same vehicle, that is, when the load is constant, the creep demand torque r is related to the set creep vehicle speed. Wherein, Ts(t)=Tm(t); Te(t)=Tc(t)=0.

Step S2: t2≤t≤t3: The driver steps on the accelerator, the control system controls the clutch from the open state to the creep point after receiving the signal of the accelerator stepping on, and the clutch torque Tc(t) is increased to drag the engine to start, and at the same time The control system controls the output torque Tm(t) of the motor to increase, so that the actual torque Ts(t) remains unchanged, and the control system issues an instruction to control the engine speed to adjust the engine speed to the starting speed v _q . In this step, the actual torque of the vehicle remains unchanged, which is Ts(t2) or Ts(t3).

In this step, the driver steps on the accelerator at time t2, and the control system sends an instruction to control the clutch to start closing at time t2' after receiving the accelerator signal, where t2<t2'<t3; at time t3, the clutch is closed to the creep point position, At this moment, the engine is started by the anti-drag of the clutch. During this process, the motor bears two parts of torque, one is the torque of the clutch, and the other is the actual torque. In other words, the clutch torque Tc(t) in this step is not used to drive the car, but to start the engine.

It should be noted that due to the randomness of the driver stepping on the accelerator, the actual torque Ts(t2) and vehicle speed at time t2 are not fixed values. In other words, at time t2, the vehicle speed has two situations: a. The creep speed, b, is equal to the set creep speed. Correspondingly, at time t2, the actual torque is Ts(t) in two cases: less than the creep required torque r or equal to the creep required torque r.

In this step, the control system controls at least the following three parts at the same time: (1) controlling the clutch to be closed from the open state to the creep point. (2) Control the clutch torque Tc(t) to gradually increase to the engine starting torque a, drag and start the engine. (3) Adjust the engine speed to the starting speed to prepare for smooth and fast connection with the gearbox input shaft.

The above-mentioned three parts are carried out at the same time, which speeds up the clutch closing process and shortens the starting time of the engine.

In this step, the control system controls the engine speed to increase to the starting speed v _q , where v _q =v _in +x, where:

v _q is a maximum value during the startup process;

x is an empirical correction value, which is a parameter well known to those skilled in the art, and its value range is commonly used by those skilled in the art. Preferably, its value is -400;

v _in is the rotational speed of the gearbox input shaft at the time of anti-drag;

The definition of anti-dragging moment: when the control system detects for the first time that the engine speed v _f (t) keeps increasing within 20ms. In other words, within 20ms, dv _f (t)/dt>0, at this time, the control system controls the clutch to close and the anti-drag engine starts.

The input shaft speed of the gearbox is calculated according to the motor speed, and the input shaft speed of the gearbox is equal to the motor speed divided by the gear ratio from the motor to the input shaft.

In this step, the control system controls the clutch torque Tc(t) to gradually increase, and the motor output torque Tm(t) to gradually increase, and:

Ts(t)+Tc(t)=Tm(t),

Ts(t2)≤r, Tc(t2)=0,

Tc(t3)=Te(t3)=a.

Wherein, a is the starting torque of the engine, that is, the torque required to start the engine, which is a constant. The value of the engine starting torque a is proportional to the opening (depth) of the accelerator: the greater the opening of the accelerator depressed by the driver, the greater the required engine starting torque a. Because the accelerator opening reflects the driver's demanded torque, the larger the accelerator opening, the greater the driver's demanded torque, and the greater the required vehicle acceleration, that is, the higher the required engine starting speed, so that the engine speed reaches the above-mentioned starting speed when the clutch is closed. , the required starting torque a is naturally larger.

Now analyze each torque in step S2:

1) Clutch torque Tc(t)

The analysis of the clutch torque Tc(t) can be divided into two stages. The first stage is from the time when the clutch receives the command to start the engine to the moment of anti-drag. This stage is to eliminate the clutch idle travel, and the clutch has not yet started to anti-drag the engine. ) is 0; the second stage is from the anti-drag moment to the clutch closing to the creep point, and the clutch torque Tc(t) is greater than 0 in this stage.

The method of determining the value of the clutch torque Tc(t) at time t in the second stage is as follows: according to the two parameters of the throttle opening and the engine speed when the control system first detects that the engine speed v _f (t) keeps increasing within 20 ms, find Two-dimensional table of clutch torque. The clutch torque two-dimensional table is a lookup table LUT, and the two coordinates of the clutch torque two-dimensional table are throttle opening and engine speed respectively, and the control system can detect the throttle opening of the car and the real-time engine speed. The rotational speed is input into MATLAB, and the input digital signal of the throttle opening and each continuous engine rotational speed can be corresponding to the abscissa and ordinate determined in the two-dimensional table through MATLAB calculation, thereby obtaining the value of the clutch torque. It should be noted that the engine speeds in the two-dimensional table take discrete values, and the real-time engine speeds received in MATLAB may not fall within the discrete values. For this situation, non-overlapping engine speeds can be designed in advance For the speed range, MATLAB corresponds the engine speed in each range to a discrete value in the two-dimensional table. The technical solution of using the MATLAB lookup table LUT is a prior art well known to those skilled in the art, and will not be repeated here.

2) The motor output torque is Tm(t)

The method for determining the value of the motor output torque Tm(t) at time t is: Tm(t)=k Tw(t), where:

k: throttle coefficient, determined according to the throttle opening and motor speed at time t, which is a parameter well known to those skilled in the art;

Tw(t): The external characteristic torque of the motor at time t, which is determined by checking the motor external characteristic table according to the motor speed at time t.

It can be known from the above that the actual torque Ts(t) in this step can be determined by the formula Ts(t)=Tm(t)-Tc(t).

Step S3: When t3<t≤t4, the clutch is closed from the creep point, the control system controls the output torque of the motor to decrease as Tm(t), the output torque of the engine increases as Te(t), and the actual torque Ts(t) of the vehicle remains unchanged, the control system adjusts the engine speed at the same time, so that the growth rate of the engine speed is consistent with the growth rate of the vehicle speed, and the engine start is completed.

During this process, at time t3, that is, the clutch creep point, the engine speed reaches the maximum value—the starting speed v _q , and then the control system controls the engine speed to adjust to the target speed, and maintains the growth rate of the engine speed and the vehicle speed during the clutch closing process The rate is consistent. The target speed is related to the gear of the gearbox, and is designed according to the depth of the accelerator, the gear of the gearbox and the current vehicle speed. The design principle is to make the engine and motor work in the high-efficiency zone.

After the start is successful, the control system controls the engine output torque Te(t) to increase gradually, and transmits it to the gearbox input shaft through the clutch, the motor output torque Tm(t) gradually decreases, and the increase of the engine output torque is equal to the motor output torque The reduction by:

Ts(t)=Tm(t)+Te(t).

When the engine speed growth rate is consistent with the vehicle speed growth rate, the engine starts successfully. After the car is started successfully, continue to adjust the torques so that when the car is running normally, the engine output torque Te(t) reaches the engine demand torque b, and the motor output torque Tm(t) reaches the motor demand torque d. The engine demand torque b and the motor demand torque d refer to the torque borne by the engine and the torque borne by the motor when the vehicle is running stably, respectively, when the accelerator signal remains unchanged. The engine demand torque b and the motor demand torque d are values distributed by the control system according to the driver's demand torque, so that the motor and engine operate in the high-efficiency zone. When the car is running normally after starting, the actual torque is equal to the driver's demand torque transmitted by the accelerator signal.

It can be seen from the above that during the process from t2 to t4, the actual torque of the car remains unchanged, which is Ts(t2), which ensures that the car starts smoothly and without setbacks. And Ts(t2)>0, dv/dt>0, that is, the vehicle speed increases steadily, which ensures the acceleration of the vehicle and prevents power interruption.

During the start-up process of the above-mentioned engine, the control system prohibits the shifting operation of the gearbox shown.

In the present invention, under the condition of high throttle and low vehicle speed (the torque demand transmitted by the throttle is greater than the maximum torque that the actual motor can provide), the engine is started by closing the clutch and calculating the speed of the input shaft of the gearbox during the closing of the clutch so that the speed of the engine is at the point where the clutch is closed. During the process, the speed is adjusted to the speed of the input shaft of the gearbox, which can speed up the clutch closing process and shorten the power interruption time. At the same time, it meets the car's demand for smooth start-up, optimizes the smoothness of automatic start-stop power, and takes into account the dynamics.

Finally, it is necessary to explain here that: the above examples are only used to further describe the technical solutions of the present invention in detail, and cannot be interpreted as limiting the protection scope of the present invention. Non-essential improvements and adjustments all belong to the protection scope of the present invention.

Claims (10)

1. The automatic starting control method of the engine of the hybrid electric vehicle is characterized in that the automatic starting control of the engine comprises the following steps:

Step S1: when t is greater than t1 and less than t2, the control system does not receive a brake or accelerator signal, the automobile is driven by the motor alone, the control system controls the output torque Tm (t) of the motor to rise, the automobile speed rises, the highest speed rise is the set creep speed, and the highest output torque Tm (t) of the motor rises to the creep required torque r;

Step S2: when t is more than or equal to t2 and less than or equal to t3, the driver steps on the accelerator, and the control system controls the clutch to move from an open state to a creeping point after receiving a signal that the accelerator is stepped onthe torque Tc (t) of the engine is increased to drag the engine to start, meanwhile, the control system controls the output torque Tm (t) of the motor to be increased, the actual torque Ts (t) is kept unchanged, and the control system sends an engine rotating speed adjusting instruction to adjust the rotating speed of the engine to a starting rotating speed v_q；

step S3: when t is more than t3 and less than or equal to t4, the clutch is closed from a creeping point, the control system controls the output torque of the motor to be Tm (t) and reduce, the output torque of the engine to be Te (t) and increase, the actual torque Ts (t) of the automobile is kept unchanged, and the control system simultaneously sends an instruction for adjusting the rotating speed of the engine to ensure that the rotating speed v of the engine is enabled to be V_f(t) rate of increase and vehicle speed v_f(t) the growth rates are consistent and the engine start is complete.

2. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in step S1, the vehicle speed is kept unchanged after reaching the set creep vehicle speed, the motor output torque Tm (t) is kept unchanged after reaching the creep required torque r, and the motor output torque Tm (t) reaches the creep required torque r when the vehicle speed reaches the set creep vehicle speed.

3. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in step S1, the clutch is kept open.

4. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: before the time t1, the automobile is in a working condition that the driver steps on the brake and releases the accelerator under the condition that the automobile speed is low or the automobile is stopped, the engine is in a stop working condition, and the clutch is in an open state.

5. The automatic engine start control method for a hybrid vehicle according to claim 4, characterized in that: at time t1, the driver releases the brake, and the control system receives the signal of brake release and then controls the output torque Tm (t) of the motor to rise and the vehicle speed to rise.

6. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in S1, Ts (t) is Tm (t); te (t) ═ Tc (t) ═ 0.

7. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in S2, v_q＝v_in+ x, wherein:

x is an approved correction value;

v_inthe rotating speed of the input shaft of the gearbox at the moment of reverse dragging;

Definition of anti-drag time: when the control system first detects the engine speed v_f(t) the time of growth is maintained for 20ms in succession.

8. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: at S2, the following parameters are satisfied:

Ts(t)+Tc(t)＝Tm(t)，

Ts(t)≤r，Tc(t2)＝0，

Tc(t3)＝Te(t3)＝a，

Where a is an engine starting torque for starting the engine.

9. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in S2, when the driver steps on the accelerator at the time of t2, the control system controls the clutch to start to close at the time of t2 'after receiving an accelerator signal, wherein the clutch is closed to a creep point position at the time of t2 < t 2' < t3, and the engine is started by the reverse dragging of the clutch at the time of t 3.

10. The automatic engine start control method for a hybrid vehicle according to claim 1, characterized in that: in S3, Ts (t) is Tm (t) + Te (t) is Ts (t 2).