An air intake manifold multi-point injection gas engine air-fuel ratio closed loop control method

Abstract

The application discloses a kind of air intake manifold multi-point injection gas engine air-fuel ratio closed-loop control method, and air quantity is controlled by throttle throttle control intake air to adjust air-fuel ratio;Adopt engine exhaust end oxygen sensor to collect air-fuel ratio λ actual Signal, and the consistency control of air-fuel ratio λ actual Actual value and target value λ target It is realized by the strategy of PI algorithm control;In order to accurately distinguish different conditions, calculate gas injection quantity by gas injection time t, effective area, gas injection pressure, gas injection temperature and other parameters.The application provides the method for determining gas injection quantity in the absence of gas flowmeter, so as to simply and effectively adjust air quantity to realize air-fuel ratio adjustment, and air-fuel ratio adjustment process will not affect output power.

Description

Technical Field

[0001] This invention belongs to the field of engine control technology, specifically a closed-loop control method for the air-fuel ratio of an intake manifold multi-point injection gas engine. Background Technology

[0002] Air-fuel ratio control in gas engines has a significant impact on performance aspects such as emissions, thermal efficiency, heat load, and reliability. Therefore, air-fuel ratio control has become an important aspect of gas engine control systems.

[0003] Currently, some patents provide methods for controlling the air-fuel ratio, such as patent CN202210523292.1, which describes a correction method, system, electronic device, and storage medium for controlling the air-fuel ratio of a vehicle. This method involves setting weighting coefficients for multiple regions, calculating the fuel self-learning fluctuation value for each region, dynamically adjusting the weighting coefficients, calculating a second fuel adaptive value, calculating a fuel characteristic learning value, and finally correcting the fuel quantity by combining the fuel characteristic learning value and the adaptive learning value.

[0004] For example, patent CN202210682813.8 describes a short-term fuel correction method for engines. This method includes: S1, obtaining a basic value of the short-term fuel correction coefficient, which is obtained by dividing the actual air-fuel ratio by the target air-fuel ratio and performing a first-order low-pass filter; S2, obtaining the short-term fuel correction coefficient based on the fuzzy correction coefficient of the short-term fuel correction error; wherein the fuzzy correction coefficient of the short-term fuel correction error is obtained by a fuzzy controller; the input of the fuzzy controller is the short-term fuel correction error and the rate of change of the short-term fuel correction error, and the output of the fuzzy controller is the fuzzy correction coefficient of the short-term fuel correction error.

[0005] For example, patent CN202210249313.5 describes a GPF regeneration control method based on a two-point oxygen sensor. This method includes: when the engine is running in the GPF regeneration zone, using a pre-controlled fuel injection quantity model to perform closed-loop control on the actual air-fuel ratio, and performing self-learning on the average value of the closed-loop fuel injection correction factor output by the pre-controlled fuel injection quantity model until the average value of the closed-loop fuel injection correction factor reaches the target value; using the self-learning value saved at the end of the self-learning to correct the pre-controlled fuel injection quantity model; and inputting an air-fuel ratio test signal into the corrected pre-controlled fuel injection quantity model to determine whether the voltage signal output by the two-point sensor meets the requirements. If so, GPF regeneration control is started.

[0006] The problem is that all the above patents control the air-fuel ratio by operating the fuel (gas) system. However, in many application environments, operating the fuel (gas) means changing the power output, which is inconsistent with the demand. Furthermore, the above patents employ intelligent control methods based primarily on self-learning, making the control methods quite complex. Secondly, the intake manifold multi-point injection gas engine is a typical gas injection structure gas engine, and the above patents do not address specific air-fuel ratio technology strategies. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a closed-loop control method for the air-fuel ratio of a multi-point injection gas engine. The aim is to adjust the air-fuel ratio by controlling the intake air volume through throttle valve control for multi-point injection gas engines; to collect the air-fuel ratio λactual signal using an oxygen sensor at the engine exhaust end, and to achieve consistent control between the actual air-fuel ratio λactual and the target value λtarget using a PI algorithm control strategy; and to accurately distinguish different operating conditions, to calculate the gas injection quantity using parameters such as gas injection duration t, effective area, gas injection pressure, and gas injection temperature.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a closed-loop control method for air-fuel ratio of a multi-point injection gas engine in an intake manifold, the key being: controlling the air-fuel ratio by adjusting the throttle position through a PI algorithm program implanted in the engine controller ECU; specifically, the throttle position adjustment amount determined by the PI algorithm is Delta_λ*delta_coef_P+ΣDelta_λ*delta_coef_I; where the gain term P is determined by Delta_λ*delta_coef_P, and the integral term I is determined by ΣDelta_λ*delta_coef_I; where Delta_λ is the difference between the target air-fuel ratio λtarget and the actual air-fuel ratio λactual; delta_coef_P is the input value in the engine controller ECU that establishes the relationship between Delta_λ and the throttle opening change delta_throttle. The one-to-one correspondence between Delta_λ and the throttle opening change delta_throttle is established in the engine controller ECU, forming the integral curve delta_coef_I, and the integral term I is ΣDelta_λ*delta_coef_I. The actual air-fuel ratio λactual is obtained by the exhaust oxygen sensor. The target air-fuel ratio λtarget is calibrated for each operating condition using a three-dimensional map with the gas injection quantity Qf and engine speed n as the vertical and horizontal axes.

[0009] As a further optimization, to obtain a more accurate engine speed, the engine speed n is acquired by an engine speed sensor.

[0010] As a further optimization, to obtain a more accurate gas injection quantity, the gas injection quantity Qf is calculated using the formula... Determined; where t is the injection duration of the injection valve, determined by the engine control unit (ECU); num is the number of cylinders in the engine; Af is the effective area of ​​the injection valve, an input parameter of the ECU; k is the gas adiabatic index k, an input parameter of the ECU; P f The pressure before the injection valve is obtained by the injection valve pressure sensor; ρ f This represents the gas density before the gas injection valve.

[0011] As a further optimization, to more accurately determine the gas density before the gas injection valve, the gas density ρf before the gas injection valve is determined by the formula... Determine; where ρ0 is the density of the gas under standard conditions; T f The temperature of the fuel gas before the injection valve is obtained through the injection valve temperature sensor.

[0012] As a further optimization, in order to ensure the gas injection effect, the pressure Pf before the injection valve is greater than 1.86 times the pressure of the intake manifold.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] The present invention provides a closed-loop control method for air-fuel ratio of a multi-point injection gas engine in an intake manifold, which provides a method for determining the gas injection quantity without a gas flow meter, thereby simply and effectively adjusting the air-fuel ratio by adjusting the air volume, and the air-fuel ratio adjustment process does not affect the output power. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system structure of Embodiment 1 of the present invention;

[0016] Figure 2 This is a parameter table for the air-fuel ratio target value λtarget in Embodiment 1 of the present invention;

[0017] Figure 3 This is the gain curve parameter table of Embodiment 1 of the present invention;

[0018] Figure 4 This is the integral curve parameter table of Embodiment 1 of the present invention;

[0019] Figure 5 This is the formula for calculating the gas density before the gas injection valve in Embodiment 1 of the present invention;

[0020] Figure 6 This is the formula for calculating the gas injection quantity in Embodiment 1 of the present invention.

[0021] Figure 1 In the diagram: 1 represents the exhaust oxygen sensor; 2 represents the speed sensor; 3.1 represents gas injection valve 1#; 3.2 represents gas injection valve 2#; 3.3 represents gas injection valve 3#; 3.4 represents gas injection valve 4#; 4 represents the pressure sensor before the injection valve; 5 represents the temperature sensor before the injection valve; 6 represents the throttle body; 7 represents the engine controller (ECU); 8 represents the throttle body opening (aperture); 9 represents the actual air-fuel ratio (λactual); 10 represents the engine speed (n); 11 represents the throttle position adjustment gain coefficient (delta_coef_P); 12 represents the throttle body position adjustment integral coefficient (delta_coef_I); 13 represents the standard gas density (ρ0); 14 represents the gas adiabatic index (K); 15 represents the effective area of ​​the injection valve (Af); 16 represents the number of cylinders (num); 17 represents the target air-fuel ratio (λtarget); 18 represents the temperature before the injection valve (Tf); 19 represents the pressure before the injection valve (Pf); 20 represents the injection valve opening duration (t). Detailed Implementation

[0022] The present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] Example 1: Please refer to Figure 1-2 ;

[0024] A closed-loop control method for air-fuel ratio in a multi-point injection gas engine is disclosed, using a four-cylinder engine using natural gas as fuel as an example. The engine controller ECU7 receives the actual air-fuel ratio λactual from the exhaust oxygen sensor 1; the engine speed n from the speed sensor 2; the pressure Pf from the injection valve inlet sensor 4; the temperature Tf from the injection valve inlet sensor 5; and the throttle position aperture from the throttle valve 6. It then inputs the standard fuel density ρ0; the fuel adiabatic index k; the effective area Af of the injection valve; the number of cylinders num; the target air-fuel ratio λtarget; the integral coefficient delta_coef_I for throttle position adjustment; and the gain coefficient delta_coef_P for throttle position adjustment, and also receives the opening duration t sent to the fuel injection valve.

[0025] Furthermore, in the intake manifold multi-point injection gas engine air-fuel ratio closed-loop control method described in this invention, the gas density before the gas injection valve is as follows: Figure 5 The formula is used for calculation, where Pf is in bar A and Tf is the absolute temperature. For natural gas under standard conditions, the standard density ρ0 is 0.7174 kg / m³. 3 When the pressure Pf before the gas injection valve is 6 bar and the temperature Tf before the gas injection valve is 300 K, the density ρf is 0.3919 kg / m³. 3 .

[0026] Furthermore, in the intake manifold multi-point injection gas engine air-fuel ratio closed-loop control method described in this invention, the gas injection quantity is as follows: Figure 6 As shown, the pressure before the gas valve in the multi-point injection gas engine of the intake manifold described in this invention should be greater than 1.86 times the pressure in the main intake manifold. This applies to an injection duration t of 0.01 s; a cylinder count of 4; and an effective gas injection valve area of ​​28 mm². 2 The pressure Pf before the gas injection valve is 6 bar; the density ρf is 0.3919 kg / m³. 3 For a natural gas adiabatic index of 1.33, the gas injection quantity Qf is 3.03g.

[0027] Furthermore, the air-fuel ratio closed-loop control method for a multi-point injection gas engine described in this invention establishes a three-dimensional map with the gas injection quantity Qf and engine speed n as the vertical and horizontal axes to calibrate the air-fuel ratio target value λtarget for each operating condition, such as... Figure 1 The engine controller ECU7 calculates Delta_λ = λtarget - λactual.

[0028] The present invention discloses a closed-loop air-fuel ratio control method for an intake manifold multi-point injection gas engine. This method uses throttle valve 6 to regulate the air volume. When Delta_λ is greater than 0, the throttle valve 6 opening (aperature) is increased to decrease the air flow rate, thereby increasing the air volume and the actual air-fuel ratio, thus maintaining consistency between the two. Conversely, when Delta_λ is less than 0, the throttle valve 6 opening (aperature) is decreased to increase the air flow rate, thereby decreasing the air volume and the actual air-fuel ratio, thus maintaining consistency between the two.

[0029] Furthermore, the air-fuel ratio closed-loop control method for a multi-point injection gas engine in the intake manifold described in this invention establishes a gain curve with Delta_λ as the abscissa and the throttle position adjustment delta_coef_P as the ordinate, as shown below. Figure 3 Establish an integral curve with Delta_λ as the abscissa and the throttle position adjustment delta_coef_I as the ordinate, as follows: Figure 4 ;

[0030] Furthermore, the air-fuel ratio closed-loop control method for a multi-point injection gas engine in the intake manifold described in this invention uses a PI algorithm to adjust the throttle position 6 aperature. The gain term P is determined by Delta_λ*delta_coef_P, and the integral term I is determined by ΣDelta_λ*delta_coef_I. Therefore, the throttle position 6 aperature adjustment amount determined by the PI algorithm is Delta_λ*delta_coef_P + ΣDelta_λ*delta_coef_I.

[0031] It should be noted that this invention mainly uses an engine controller (ECU), an exhaust oxygen sensor, a throttle position sensor, an injection valve pressure and temperature sensor, an injection valve injection duration sensor, and a speed sensor to form a control system to achieve the above-mentioned method. Specifically, a three-dimensional map is established to represent engine speed n, gas injection quantity Qf, and air-fuel ratio target value λtarget, achieving a correspondence between engine speed n, gas injection quantity Qf as input conditions, and air-fuel ratio target value λtarget as output values. Engine speed n is acquired by an engine speed sensor. The pressure Pf and temperature Tf before the injection valve are acquired by injection valve pressure and temperature sensors. The injection duration t is the ECU confirmation signal; the effective area Af of the gas injection valve is an ECU input parameter; the number of gas injection valves num is an ECU input parameter; the gas adiabatic index k is an ECU input parameter; the gas density ρf before the injection valve is a calculated value by the ECU; and the gas density ρ0 under standard conditions is an ECU input parameter. The throttle opening change delta_throttle can be determined according to... Figure 3 , Figure 4 Calculate P and I by looking up the table, and then add them together.

[0032] The above solution has the following effects:

[0033] The present invention provides a closed-loop control method for air-fuel ratio of a multi-point injection gas engine in an intake manifold, which provides a method for calculating the gas injection quantity without a gas flow meter, thereby simply and effectively adjusting the air volume to achieve air-fuel ratio regulation without affecting the output power.

[0034] The parts of this invention not described in detail are prior art; for those skilled in the art, the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A closed-loop control method for air-fuel ratio in a multi-point injection gas engine with an intake manifold, characterized in that: The air-fuel ratio is controlled by adjusting the throttle position through a PI algorithm program implanted in the engine controller (ECU); specifically, the throttle position adjustment amount determined by the PI algorithm is Delta_λ*delta_coef_P+ΣDelta_λ*delta_coef_I. Among them, the gain term P is determined by Delta_λ*delta_coef_P, and the integration term I is determined by ΣDelta_λ*delta_coef_I; Where Delta_λ is the difference between the target air-fuel ratio λtarget and the actual air-fuel ratio λactual; delta_coef_P is the gain curve delta_coef_P formed by establishing a one-to-one correspondence between Delta_λ and the throttle opening change delta_throttle in the engine controller ECU; then the gain term P is Delta_λ*delta_coef_P; and the integral curve delta_coef_I is formed by establishing a one-to-one correspondence between Delta_λ and the throttle opening change delta_throttle in the engine controller ECU; then the integral term I is ΣDelta_λ*delta_coef_I. The actual air-fuel ratio λactual is obtained by collecting data from the exhaust oxygen sensor. Among them, the target air-fuel ratio λtarget is calibrated for each operating condition using a three-dimensional map with the gas injection quantity Qf and engine speed n as the vertical and horizontal axes. The gas injection quantity Qf is given by the formula Sure; Where t is the injection duration of the injection valve, determined by the engine control unit (ECU); num is the number of cylinders in the engine; Af is the effective area of ​​the injection valve, an input parameter of the ECU; k is the gas adiabatic index k, an input parameter of the ECU; P f The pressure before the injection valve is obtained by the injection valve pressure sensor; ρ f The gas density before the gas injection valve; The gas density ρ before the gas injection valve f From the formula Sure; Where ρ0 is the density of the gas under standard conditions; T f The temperature of the fuel gas before the injection valve is obtained through the injection valve temperature sensor.

2. The closed-loop control method for air-fuel ratio of a multi-point injection gas engine in an intake manifold according to claim 1, characterized in that: The engine speed n is obtained by the engine speed sensor.

3. The closed-loop control method for air-fuel ratio of a multi-point injection gas engine in an intake manifold according to claim 1, characterized in that: The pressure P before the injection valve f It is more than 1.86 times the intake manifold pressure.

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