CN104295387B - A kind of matter adjustable type engine start control method based on command torque - Google Patents

Abstract

The invention discloses a quality-adjusted engine starting control method based on indicated torque to solve the problem in the prior art that it is difficult to realize precise control of fuel injection quantity in the engine starting process and affect engine startability. Obtain the starting drag torque of the engine at different crankshaft speeds and coolant temperatures through experiments; determine the target angular acceleration function during the starting process according to the engine starting control requirements, and calculate the acceleration resistance torque to realize the control of the engine speed and starting during the starting process. Time control; calculate the actual angular acceleration of the engine according to the change of the actual crankshaft speed of the engine, and determine the compensation torque from the deviation between the actual angular acceleration of the engine and the target angular acceleration; add the starting drag torque, acceleration resistance torque and compensation torque to obtain the starting demand The indicated torque; according to the indicated efficiency, the required indicated torque is converted into the fuel injection quantity. The method can ensure the optimal fuel injection quantity required for the starting process under various starting conditions.

Description

A quality-adjusted engine starting control method based on indicated torque

technical field

The present invention relates to the control of a combustion engine, in particular to a control strategy for the fuel injection mode in the starting process of a mass-regulated engine whose torque is indicated based on demand and whose starting time can be controlled

Background technique

For the control of the fuel injection mode during the starting process of the mass-regulated engine, the optimal fuel injection quantity is supplied relative to the air volume entering the cylinder, so that it forms a mixed gas in the cylinder and burns, pushing the piston to do work, and overcoming the internal resistance of the engine. Drive the crankshaft to make the engine speed reach the expected target value.

Whether it starts normally and the change of the engine speed during the starting process is directly related to the set fuel injection amount and its injection method. Usually the fuel injection quantity in the starting process is determined by the engine bench calibration test. Due to the different control strategies in the starting process, the starting injection quantity and injection method are very different. If the fuel injection amount is too small and the injection method is unreasonable, the normal starting process cannot be completed; otherwise, too much fuel injection will not only increase fuel consumption, which is not conducive to energy saving, but also cause increased emissions of hydrocarbons, carbon monoxide, and particulates. Therefore, according to the specific conditions of the starting conditions, setting a reasonable fuel injection amount and adopting a reasonable injection method can not only effectively control the starting time, but also effectively control the emission of hydrocarbons, carbon monoxide and particulates during the starting process, so as to adapt to continuous Strict vehicle engine energy saving and emission reduction requirements.

The starting environmental conditions are more complicated. Due to the difference in coolant temperature, injection advance angle, injection pressure and fuel injection mode, the engine indication efficiency is quite different, and the fuel injection amount required to complete the starting process is also different. The traditional starting control method, in order to ensure reliable starting, usually only simply compensates a certain amount of fuel injection according to the starting state, and it is difficult to realize the precise control of the fuel injection amount during the starting process, so it directly affects the startability of the engine. With the development of low-carbon automobiles, in order to improve the starting performance of vehicle engines, a perfect starting control strategy is necessary.

Contents of the invention

In order to solve the problem in the prior art that it is difficult to realize the precise control of the fuel injection quantity in the engine starting process and affect the engine startability, the invention provides a method for controlling the starting fuel injection quantity based on demand indicated torque and indicated efficiency.

In order to solve the problems of the technologies described above, the present invention is achieved by adopting the following technical solutions:

A quality-regulated engine starting control method based on indicated torque, characterized in that it comprises the following steps:

Step 1. Obtain the starting drag torque Trq _d at different crankshaft speeds n _crank and coolant temperature T _w of the engine through experiments; determine the starting drag torque Trq according to the crankshaft speed n _crank and coolant temperature T _w when the engine starts _d ;

Step 2. Determine the target angular acceleration function β ₀ (t) of the starting process according to the starting control requirements of the engine, and calculate the acceleration resistance torque Trq _I based on the target angular acceleration β ₀ during the starting process, so as to realize the control of the engine speed and starting time control.

Step 3. Calculate the actual angular acceleration β of the engine according to the change of the actual crankshaft speed n _crank of the engine, and determine the compensation torque Trq _c from the deviation between the actual angular acceleration β of the engine and the target angular acceleration β ₀ ; the actual angular acceleration β and the target angular acceleration β ₀ If the deviation is positive, the compensation torque will decrease; if the deviation is negative, the compensation torque will increase.

Step 4: Add the starting drag torque Trq _d , the acceleration resistance torque Trq _I and the compensation torque Trq _c to obtain the indicated torque Trq _i required for starting, that is, Trq _i =Trq _d +Trq _I +Trq _c ;

Step 5. According to the indicated efficiency, convert the demand indicated torque Trq _i into the fuel injection quantity q. The fuel injection quantity q consists of two parts: the basic fuel injection quantity q ₀ and the fuel injection correction quantity △q:

Further technical scheme is as follows:

The specific process of step two is:

a. According to the expected starting time t ₀ set according to the requirements of the starting time, set the starting injection speed n ₁ and the starting process finishing speed n ₂ according to the characteristics of the starter motor and engine; obtain the moment of inertia I of the target engine.

b. According to the starting control requirements of the engine, determine the target angular acceleration function β ₀ (t), and the integral of β ₀ (t) within the expected starting time t ₀ is the relationship between the starting process completion speed n ₂ and the starting injection speed n ₁ difference, ie ${\∫}_0^{t_0}{\mathrm{\β}}_0\left(t\right)\mathrm{dt}={\mathrm{no}}_2-{\mathrm{no}}_1;$

c. Calculate the acceleration resistance torque Trq _I by using the formula Trq _I =I·β ₀ , where: β ₀ is the target angular acceleration, and I is the moment of inertia of the engine.

The specific process of step five is:

a. According to the indicated efficiency η _i0 of the engine under standard normal temperature starting conditions, calculate the base fuel injection quantity q ₀ required for the required indicated torque Trq _i , Where π is the circumference ratio, τ is the number of strokes, _i is the number of cylinders, and Hu is the low calorific value of the fuel;

b. When the starting condition changes, according to the change of the indicated efficiency, the fuel injection quantity △q is corrected, that is k is the indicator efficiency correction factor, obtained through experiments.

c. Add the basic fuel injection amount q ₀ and the fuel injection correction amount Δq to obtain the starting fuel injection amount q, q=q ₀ +Δq.

Compared with the prior art, the present invention has the following beneficial effects: the starting process is carried out strictly according to the angular acceleration calculated from the expected starting time, and a compensation link is attached to ensure the best indication required for the starting process under various environmental conditions Torque, while ensuring the target starting time, the reliability of the starting process is high; by setting different expected starting times, the actual starting time of the engine can be changed; the fuel injection amount in the starting process is converted from the demand indicated torque. When the injection parameters or combustion conditions are changed, it is only necessary to adjust the indicated efficiency correction factor to ensure the optimal fuel injection quantity required for the starting process under various starting conditions; the starting process curve can be adjusted by using different target angular acceleration algorithms, Realize the smooth transition from starting to idling and other working conditions.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is the basic control flowchart of the patent of the present invention

Fig. 2 is the rendering of Embodiment 1 of the patent of the present invention

Fig. 3 is the effect drawing of embodiment two of the patent of the present invention

detailed description

In order to introduce the content of the present invention in detail, some related concepts are defined below:

Definition 1: Indicated torque refers to the output torque of the crankshaft that is equivalent to the indicated work obtained by the conversion of heat and work in one working cycle of the cylinder. In the starting phase, the required indicated torque is used to overcome the resistance torque and inertia resistance torque during engine starting, represented by Trq _i .

Definition 2: Starting drag torque refers to the torque provided by the engine when the engine stops at a certain stable coolant temperature, and the motor is used to drag the engine to maintain a certain starting speed, expressed by Trq _d .

Definition 3: Acceleration resistance torque (or inertia resistance torque) refers to the torque required to overcome the engine rotational inertia when the engine speed increases during the starting process. The acceleration resistance torque is the product of the engine moment of inertia and the angular acceleration of the crankshaft, represented by Trq _I.

Below in conjunction with specific embodiment the present invention is described in detail:

Embodiment one:

The quality-adjusted engine starting control based on indicated torque of the present invention includes the following steps:

Step 1. Obtain the relationship between engine starting drag torque Trq _d , crankshaft speed n _crank and coolant temperature T _w through experiments, and combine the experimentally obtained starting drag torque Trq _d with crankshaft speed n _crank and coolant temperature T The relationship between _w , the starting drag torque Trq _d is determined according to the current crankshaft speed n _crank of the engine and the coolant temperature T _w . Specifically, in this embodiment, at the coolant temperature T _w , the fuel injection is stopped, and the electric dynamometer is converted to the electric motor to drag the engine back to a given crankshaft speed n _crank , and the coolant temperature T _w is kept constant. The torque required by the electric dynamometer is the starting drag torque Trq _d ; adjust the coolant temperature T _w and the crankshaft speed n _crank to other values to obtain the corresponding starting drag torque Trq _d , thus establishing The relationship between starting drag torque Trq _d , crankshaft speed n _crank and coolant temperature T _w .

Step 2: Determine the target angular acceleration function β ₀ (t) in the starting process according to the engine starting control requirements, and calculate the acceleration resistance torque Trq _I based on the target angular acceleration β ₀ in the starting process. Including the following three specific steps:

a: Set the expected starting time t ₀ according to the requirements of the starting time, set the starting injection speed n ₁ and the starting process completion speed n ₂ according to the characteristics of the starter motor and engine; obtain the moment of inertia I of the target engine. The start speed _n1 is the speed at which the starter motor drives the engine to start fuel injection; the start end speed _n2 is the set speed at which the engine leaves the starting state. In this embodiment, t ₀ =3s, n ₁ =250r/min; n ₂ =750r/min, I=0.5kg·m ² .

b: According to the starting control requirements of the engine, determine the target angular acceleration function β ₀ (t), the target angular acceleration β ₀ satisfies its integral within the expected starting time t ₀ is the starting process completion speed n ₂ and the starting injection speed n ₁ difference, that is In this embodiment, n ₂ =750r/min, n ₁ =250r/min, I=0.5kg·m ² , and the method of decreasing target angular acceleration during the starting process is adopted, π is the circumference ratio, and t is the relative moment of the current relative to the start-up phase. The target angular acceleration β ₀ decreases with the increase of the relative time t, and when the relative time t=t ₀ , the target angular acceleration β ₀ is zero.

c: Based on the target angular acceleration β ₀ and the moment of inertia I of the engine, the acceleration resistance torque Trq _I is calculated using the formula Trq _I =I·β ₀ . In this embodiment, Trq _I =5.8(3-t).

Step 3: Calculate the actual angular acceleration β of the engine according to the actual crankshaft speed n _crank of the engine, and determine the compensation torque Trq _c according to the deviation between the actual angular acceleration β of the engine and the target angular acceleration β ₀ . The actual angular acceleration β is obtained by differential calculation of the crankshaft speed n _crank , namely π is the circumference ratio, and t is the relative moment of the current relative to the start-up phase. If the actual angular acceleration β is greater than the target angular acceleration β ₀ calculated in step 4, the compensation torque Trq _c decreases, and if the actual angular acceleration β is smaller than the target angular acceleration β ₀ calculated in step 4, the compensation torque Trq _c increases. In this embodiment, the compensation torque I is the moment of inertia of the engine, F _c is the compensation coefficient, t is the relative moment of the current relative to the starting phase, t ₀ is the set expected starting time, which is 3s, I=0.5kg·m ² , F _c =1 ,So have The compensation coefficient F _c can be adjusted according to the actual engine.

Step 4: Obtain the indicated torque Trq _i required for starting. The required indicated torque is the sum of starting drag torque Trq _d , acceleration resistance torque Trq _I , and compensation torque Trq _c , that is, Trq _i =Trq _d +Trq _I +Trq _c ;

Step 5: Convert the required indicated torque Trq _i into the fuel injection quantity q according to the indicated efficiency. The fuel injection quantity q is composed of two parts: the basic fuel injection quantity q ₀ and the fuel injection correction quantity Δq. Including the following three specific steps:

a: According to the indicated efficiency η _i0 of the engine under standard normal temperature starting conditions (GB/T18297-2001 "Automotive Engine Performance Test Method"), calculate the base fuel injection quantity q ₀ required for the required indicated torque Trq _i , Where π is the circumference ratio, τ is the number of strokes, _i is the number of cylinders, and Hu is the lower calorific value of the fuel. In this embodiment, the number of strokes τ=4, and the number of cylinders i=4.

b: When the starting condition changes, the fuel injection correction amount Δq is calculated according to the change of the indicated efficiency. Where k _η is the indicator efficiency correction factor, obtained through experiments.

c: Add the calculated base fuel injection amount q0 and the fuel injection correction amount Δq to obtain the starting fuel injection amount _{q =} q0+Δq.

Embodiment two:

The quality-adjusted engine starting control based on indicated torque of the present invention includes the following steps:

Step 1. Obtain the relationship between engine starting drag torque Trq _d , crankshaft speed n _crank and coolant temperature Tw through experiments, and combine the experimentally obtained starting drag torque _{Trq d} with crankshaft speed n _crank and coolant temperature T The relationship between _w , the starting drag torque Trq _d is determined according to the current crankshaft speed n _crank of the engine and the coolant temperature T _w . Specifically, in this embodiment, at the coolant temperature T _w , the fuel injection is stopped, and the electric dynamometer is converted to the electric motor to drag the engine back to a given crankshaft speed n _crank , and the coolant temperature T _w is kept constant. The torque required by the electric dynamometer is the starting drag torque Trq _d ; adjust the coolant temperature T _w and the crankshaft speed n _crank to other values to obtain the corresponding starting drag torque Trq _d , thus establishing The relationship between starting drag torque Trq _d , crankshaft speed n _crank and coolant temperature T _w .

Step 2: Determine the target angular acceleration function β ₀ (t) in the starting process according to the engine starting control requirements, and calculate the acceleration resistance torque Trq _I based on the target angular acceleration β ₀ in the starting process. Including the following three specific steps:

a: Set the expected starting time t ₀ according to the requirements of the starting time, set the starting injection speed n ₁ and the starting process completion speed n ₂ according to the characteristics of the starter motor and engine; obtain the moment of inertia I of the target engine. The start speed _n1 is the speed at which the starter motor drives the engine to start fuel injection; the start end speed _n2 is the set speed at which the engine leaves the starting state. In this embodiment, t ₀ =3s, n ₁ =250r/min; n ₂ =750r/min, I=0.5kg·m ² .

b: Determine the target angular acceleration function β ₀ (t) according to the engine start control requirements. The target angular acceleration function β ₀ (t) satisfies that its integral within the expected starting time t ₀ is the difference between the starting process completion speed n ₂ and the starting injection speed n ₁ , namely In this embodiment, n ₂ =750r/min, n ₁ =250r/min, I=0.5kg·m ² , t ₀ =2s, and the method of constant target angular acceleration during starting is adopted, namely π is the circumference ratio, and t is the relative moment of the current relative to the start-up phase.

c: Calculate the acceleration resistance torque Trq _I by using the formula Trq _I =I·β ₀ , where: β ₀ is the target angular acceleration, and I is the moment of inertia of the engine. In this embodiment: Trq _I =13.09 (kg·m).

Step 3: Calculate the actual angular acceleration β of the engine according to the actual crankshaft speed n _crank of the engine, and determine the compensation torque Trq _c according to the deviation between the actual angular acceleration β of the engine and the target angular acceleration β ₀ . The actual angular acceleration β is obtained by differential calculation of the crankshaft speed n _crank , namely π is the circumference ratio. In this embodiment, the compensation torque I is the moment of inertia of the engine, which is 0.5kg·m ² , F _c is the compensation coefficient, which is taken as 1, t is the relative moment of the current relative to the start of the start phase, and t ₀ is the set expected start time, which is 2s, so The compensation coefficient F _c can be adjusted according to the actual engine.

Step 4: Obtain the indicated torque Trq _i required for starting. The required indicated torque is the sum of starting drag torque Trq _d , acceleration resistance torque Trq _I , and compensation torque Trq _c , that is, Trq _i =Trq _d +Trq _I +Trq _c ;

Step 5: Convert the required indicated torque Trq _i into the fuel injection quantity q according to the indicated efficiency. The fuel injection quantity q is composed of two parts: the basic fuel injection quantity q ₀ and the fuel injection correction quantity Δq. Including the following three specific steps:

a: According to the indicated efficiency η _i0 of the engine under standard normal temperature starting conditions (GB/T18297-2001 "Automotive Engine Performance Test Method"), calculate the base fuel injection quantity q ₀ required for the required indicated torque Trq _i , Where π is the circumference ratio, τ is the number of strokes, _i is the number of cylinders, and Hu is the lower calorific value of the fuel. In this embodiment, the number of strokes τ=4, and the number of cylinders i=4.

b: Calculate the fuel injection correction amount △q when the starting condition changes. k _η is the indicator efficiency correction factor, obtained through experiments.

c: Add the calculated base fuel injection amount q0 and the fuel injection correction amount Δq to obtain the starting fuel injection amount _{q =} q0+Δq.

Embodiment 1 and Embodiment 2 adopt different expected starting times and different target angular acceleration functions β ₀ (t), the target angular acceleration law of the starting process is different, the change law of the acceleration resistance torque is also different, and the speed of the starting process The changes are also different, and the starting effects are shown in Figure 2 and Figure 3 respectively.

Claims (3)

1. the matter adjustable type engine start control method based on command torque, it is characterised in that comprise the steps:

Step one, by experiment acquisition electromotor difference speed of crankshaft n_crankAnd coolant temperature T_wUnder starting drag torque Trq_d; Speed of crankshaft n during according to engine start_crankWith coolant temperature T_wDetermine starting drag torque Trq_d;

Step 2, control requirement according to the starting of electromotor, it is determined that the target angular acceleration function �� of starting process₀T (), based on the target angular acceleration �� of starting process₀, calculate acceleration resistance square Trq_I, it is achieved the control to engine speed in starting process and starting time;

Step 3, according to electromotor actual crank rotating speed n_crankChange calculations electromotor actual angular acceleration ��, by electromotor actual angular acceleration �� and target angular acceleration ��₀Deviation determine compensation torque Trq_c; Actual angular acceleration �� and target angular acceleration ��₀Deviation be just, compensate torque reduce, deviation be negative, then compensation torque increase;

Step 4, general start drag torque Trq_d, acceleration resistance square Trq_IWith compensation torque Trq_cIt is added the command torque Trq obtaining starting demand_i, i.e. Trq_i=Trq_d+Trq_I+Trq_c;

Step 5, according to indicated efficiency by demand command torque Trq_iBeing converted to fuel injection amount q, fuel injection amount q is by basic fuel emitted dose q₀Form with fuel injection correction amount �� q two parts.

2. a kind of matter adjustable type engine start control method based on command torque described in claim 1, it is characterised in that the detailed process of step 2 is as follows:

A. the expection starting time t set according to the requirement of starting time₀, set starting according to starting motor and engine characteristics and start to spray rotating speed n₁, starting process complete rotating speed n₂; Obtain the rotary inertia I of target engine;

B. requirement is controlled according to the starting of electromotor, it is determined that target angular acceleration function ��₀(t), ��₀T () meets at expection starting time t₀Interior integration is that starting process completes rotating speed n₂Start to spray rotating speed n with starting₁Difference, namely

C. formula Trq is utilized_I=I ��₀Calculate acceleration resistance square Trq_I, wherein: ��₀For target angular acceleration, I is engine moment inertia.

3. a kind of matter adjustable type engine start control method based on command torque described in claim 1, it is characterised in that the detailed process of step 5 is as follows:

A. the indicated efficiency �� of electromotor when according to standard cold starting_i0Calculating demand command torque Trq_iRequired basic fuel emitted dose q₀,Wherein �� is pi, and �� is number of stroke, and i is number of cylinders, H_uFor lower calorific value of fuel;

B. when starting conditions changes, the change according to indicated efficiency, revise fuel injection amount �� q, namelyK is indicated efficiency modifying factor, obtains by experiment;

C. by basic fuel emitted dose q₀It is added with fuel injection correction amount �� q and obtains starting fuel emitted dose q, q=q₀+��q��