KR100476198B1 - Method for controlling post injection of common rail injection system in diesel vehicle - Google Patents

Abstract

It is for the calculation of the amount of post-injection fuel for the activation and regeneration of the purification system (catalyst) in the diesel common rail injection system and the control of the injection holding time.

The present invention is to calculate the mass of the basic exhaust gas from the current engine speed and the fuel amount of the current engine at the start-up state, and multiply the calculated basic exhaust gas mass by the experience value (weighting factor) according to the cooling water temperature and atmospheric pressure A process of estimating the mass of the exhaust gas that is currently being discharged and multiplying the estimated mass of the exhaust gas by the required fuel amount per unit mass of the exhaust gas with respect to the engine speed and the current engine fuel amount to determine a post injection basic fuel amount. Process and multiplying the required correction values according to the variables of cooling water temperature, intake air amount, and catalyst temperature to determine the final after-injection demand, and controlling the fuel injection by calculating the duration of the solenoid valve according to the determined after-injection amount. It includes the process of doing.

Description

TECHNICAL FOR CONTROLLING POST INJECTION OF COMMON RAIL INJECTION SYSTEM IN DIESEL VEHICLE}

The present invention relates to a diesel common rail injection system, and more particularly, to control the after injection amount of the diesel common rail injection system for the calculation of the amount of post injection fuel for activation and regeneration of the purification system (catalyst) and the control of the injection holding time. It is about a method.

In general, the diesel engine is very economical compared to the gasoline engine, the fuel economy is used in a variety of applications, and is currently being used in RV vehicles and passenger cars, the scope of application is rapidly expanding.

In order to apply a diesel engine to a passenger car, miniaturization and high speed must be accompanied. However, as miniaturization and high speed operation are performed, the time and space of fuel and air mixing are reduced, which leads to a lot of difficulties in optimizing the flow field and the spraying station.

In order to solve this problem, a common rail injection system is provided in which electron atomization and high pressure technology are applied to a fuel injection system to control fuel atomization, proper timing and injection amount of fuel.

The common rail injection system provides high pressure injection compared to the low pressure injection by the conventional cam driving method, and precisely control the injection timing to improve fuel efficiency and stabilize the exhaust gas.

The injection method of the common rail injection system includes pilot injection, main injection, and post injection. Pilot injection is performed by injecting fuel before the main injection is performed. Promotes good combustion, reduces noise caused by direct injection, reduces emissions and stabilizes combustion. Main injection is to generate actual engine output. Engine torque, engine speed, cooling water temperature, intake temperature, The injection amount is determined by the conditions such as atmospheric pressure.

The post-injection is an injection following the main injection, which injects the amount of fuel calculated during the period of up to 200 DEG in the expansion stroke or the exhaust stroke to the exhaust gas side.

Unlike the pilot injection or the main injection, the injected fuel is evaporated by the residual heat of exhaust gas instead of being burned in the cylinder, recycled to the combustion chamber through the EGR system, and performs the role of pilot injection. The engine induces the activation of the catalyst in the purification system (catalyst), which is limited in low temperature activation of the catalyst in the purification system (catalyst) due to the low temperature of the exhaust gas, thereby exhausting nitrogen oxide (NOx) and hydrocarbon (HC) series emissions. It suppresses the occurrence.

In the case of post-injection for activating the purification system as described above, a separate injection device (injector) or urea injection used in SCR is used, and the injection amount is determined according to the engine operating state and the catalyst temperature. In case of applying SCR for the injection, the cost burden of the installation is increased, and the complexity of the installation of the separate injection device has many problems in the practical application, and the determination of the injection amount after purification is not controlled, which leads to deterioration of fuel efficiency and The large amount of exhaust gas does not satisfy the exhaust gas regulation.

The present invention has been invented to solve the above problems, the object of which is to estimate the amount of exhaust gas according to the engine state in the diesel common rail injection system, calculate the required amount of after-injection, and then correct the fuel amount according to the activation of the catalyst By calculating the optimum after-injection fuel amount to control the post-injection duration, the exhaust gas is stabilized by stable catalyst activation and regeneration.

In addition, the present invention is intended to simplify the system and reduce the cost by performing the post-injection through the basic fuel injector.

The present invention for achieving the above object comprises the steps of calculating the mass of the basic exhaust gas from the current engine speed and the current fuel amount in the start-up state; Estimating the mass of the exhaust gas currently discharged by multiplying the calculated basic exhaust gas mass by an empirical value (weight factor) according to cooling water temperature and atmospheric pressure; Determining a post injection base fuel amount by multiplying the estimated mass of exhaust gas by a required fuel amount per unit mass of exhaust gas with respect to an engine speed and a current engine fuel amount; Determining a final post injection demand amount by multiplying a required correction value according to a variable of cooling water temperature, intake air amount and catalyst temperature; It provides a post injection amount control method of the diesel common rail injection system comprising the step of controlling the fuel injection by calculating the duration of the solenoid valve according to the determined after injection amount.

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Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As can be seen in Figure 1, the after injection amount control device of the diesel common rail injection system according to the present invention, the pressure detection unit 10, the engine speed detection unit 20, the cooling water temperature detection unit 30, the atmospheric pressure detection unit 40 , The catalyst temperature detector 50, the intake air amount detector 60, the controller 70, and the injector 80, the pressure detector 10 comprises a piezoelectric piezoelectric element and detects the pressure in the common rail to control the controller 70. ) As information for adjusting the fuel injection timing.

The engine speed detection unit 20 includes a magnetic pickup sensor as a crank position sensor, and detects the rotation speed of the crankshaft and provides information on the control unit 70.

The cooling water temperature detection unit 30 is a cooling water temperature sensor and detects the temperature of the cooling water circulating in the engine and the radiator and provides the information to the controller 70 to correct the increase or decrease of the fuel amount according to the water temperature.

The atmospheric pressure detection unit 40 is installed at the intake manifold inlet side by the atmospheric pressure sensor, detects the atmospheric pressure of the region driven from the air pressure information at the intake manifold inlet, and provides it to the controller 70 side as information for fuel amount correction.

The catalyst temperature detector 50 is a temperature sensor installed at the front of the catalyst, and detects the temperature of the catalyst device activated by the exhaust gas and provides the information to the controller 70. The intake air amount detector 60 The intake air amount sensor measures the amount of air flowing into the intake manifold to calculate the amount of fuel, and provides information about the amount to the controller 70.

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The controller 70 analyzes the detected information, calculates the fuel amount, adjusts the injection timing, estimates the amount of exhaust gas according to the engine state for activation and regeneration of the purification system (catalyst device), and calculates the amount of fuel. Estimates the required fuel quantity for the after injection, taking into account the cooling water temperature and atmospheric pressure, and calculates the required amount for the after injection by adding the fuel amount required for catalyst activation to the estimated value, and then considering the fuel pressure in the common rail. The injection duration is determined. The driving time of the injector 80 is controlled.

The injector 80 is opened and closed for a set time according to the control signal applied from the controller 70 to inject the amount of fuel calculated in each combustion chamber during pilot injection, main injection and post injection.

In the diesel common rail injection system according to the present invention including the functions as described above, the operations for pilot injection and main injection are the same or similar to those of the conventional operation, and thus the description of the operation is omitted and the post injection control is performed. The operation will be described with reference to FIG. 2 as follows. Engine state information such as pressure, engine speed, coolant temperature, atmospheric pressure, intake air amount, etc. in the common rail detected by the control unit 70 in a diesel vehicle having a common rail injection system. In order to activate or regenerate the purification system (catalyst) in the state where main injection is performed in the optimum state according to the present invention, the control unit 70 controls the common rail pressure, engine speed, coolant temperature, atmospheric pressure, suction Engine state information such as air volume is detected (S101).

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Subsequently, the controller 70 extracts the basic exhaust gas mass by analyzing the current engine speed detected through the set algorithm and the amount of fuel at the current engine condition through a two-dimensional map table set through an engine test (S102). ), The estimated mass of the exhaust gas is determined by calculating the extracted basic exhaust gas mass based on the correction value according to the temperature and atmospheric pressure of the cooling water (S103).

When the estimated mass of the exhaust gas is determined as described above, the required fuel amount per unit mass of the exhaust gas is extracted through the two-dimensional map table in which the current engine speed and the fuel amount at the current engine condition are set through an engine test. The basic required fuel amount at the time of post injection is determined by calculating with the estimated mass of exhaust gas (S104).

When the basic required fuel amount at the time of post-injection is determined as described above, it is determined whether the temperature of the catalyst is detected from the catalyst sensor (S105).

In step S105, the catalyst sensor is mounted, and when the temperature is detected, the detected catalyst temperature is analyzed through the set table to perform correction according to the catalyst temperature (S107), and the catalyst temperature is not detected because the catalyst temperature sensor is not installed. If not, the catalyst temperature in the purification system (catalyst) is calculated according to engine conditions such as engine speed, fuel amount, etc., and the assumed catalyst temperature is detected (S106), and then corrected according to the assumed catalyst temperature (S107).

When the correction according to the catalyst temperature is applied in the above, the correction value for the current intake air amount is added to this value (S108) to extract the actual post injection demand amount (S109).

If the actual after-spray demand is calculated in consideration of the pressure of the common rail to determine the duration (S110) and then the injection after the injection amount calculated through the drive control of the injector 80 to the expansion stroke or exhaust stroke of each combustion chamber The above description will be described with reference to FIG. 3 as follows. According to the current engine speed and the current engine fuel amount, the mass of the basic exhaust gas discharged in the current state at the point '1' is determined. This value is multiplied by the empirical value (weighted factor of 0 to 1) according to the coolant temperature at point '2', and multiplied by the empirical value (weighted factor of 0 to 1) at atmospheric pressure at point '3'. The estimated mass of the exhaust gas is calculated, and the amount of fuel required per unit mass of exhaust gas to raise the exhaust temperature for the regeneration of the particulate matter purification device or DeNox catalyst, etc. From the engine speed and the current engine fuel amount, it is calculated from the empirical secondary table value and multiplied by the estimated exhaust gas mass at the point '4' to calculate the presently required after-injection basic fuel amount. Since the amount of fuel required may vary depending on the amount of intake air, the final after injection requirement is adjusted by applying the required value correction value extracted through the catalyst temperature (select sensor or model value) and the one-dimensional table value according to the amount of intake air. Since the fuel amount is controlled by the duration of solenoid valve control, the final injection is finally controlled in a two-dimensional table according to the rail pressure to control post injection.

As described above, in the diesel engine having the common rail injection system, the determination of the post-injection amount for activation or regeneration of the purification system (catalyst) is processed with a simple control logic without additional hardware, thereby providing reliability of the system. Post-injection is carried out without an injector to reduce production costs.

1 is a configuration block diagram of the after injection fuel amount control device of the diesel common rail injection system according to the present invention.

Figure 2 is a flow chart for the after injection fuel amount control performance in the diesel common rail injection system according to the present invention. Figure 3 is a flow chart for the after injection fuel amount control in the diesel common rail injection system according to the present invention.

Claims (9)

delete delete Calculating a mass of the basic exhaust gas from the current engine speed and the current fuel amount in the starting state; Estimating the mass of the exhaust gas currently discharged by multiplying the calculated basic exhaust gas mass by an empirical value (weight factor) according to cooling water temperature and atmospheric pressure; Determining a post injection base fuel amount by multiplying the estimated mass of exhaust gas by a required fuel amount per unit mass of exhaust gas with respect to an engine speed and a current engine fuel amount; Determining a final post injection demand amount by multiplying a required correction value according to a variable of cooling water temperature, intake air amount and catalyst temperature; And controlling fuel injection by calculating a duration of the solenoid valve according to the determined post injection amount. delete delete The method of claim 3, If the correction of the cooling water temperature is not applied in determining the after-injection demand amount, after the catalyst temperature according to the engine condition is calculated by applying a correction according to the catalyst temperature, the after injection amount control method of the diesel common rail injection system. The method of claim 3, The post-injection duration control method of the diesel common rail injection system, characterized in that the post injection injection duration is determined in consideration of the pressure in the common rail to the determined after-injection demand. The method of claim 6, Wherein the correction according to the catalyst temperature is the catalyst diagnostic temperature sensor is equipped with a post injection amount control method of the diesel common rail injection system, characterized in that for performing the correction by analyzing the temperature sensor value through a set table. The method of claim 6, And the correction according to the catalyst temperature is corrected by using the assumed catalyst temperature converted from the engine speed and the fuel amount when there is no catalyst diagnosis temperature sensor.