JP2016191308A - Exhaust gas estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively improve estimation accuracy of NOx concentration discharged from an engine.SOLUTION: An exhaust gas estimation device for estimating NOx concentration in exhaust gas discharged from an internal combustion engine 10 includes: a reference NOx concentration value calculation unit 51 configured to calculate a reference NOx value in exhaust gas discharged from the internal combustion engine 10 on the basis of a rotational frequency Ne and a fuel injection amount Q of the internal combustion engine 10; and an estimation NOx concentration value calculation unit 52 configured to calculate an estimation NOx concentration value in exhaust gas discharged from the internal combustion engine 10 by multiplying the reference NOx concentration value by a first predetermined correction value set based on the fuel injection timing of the internal combustion engine 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust gas estimation device, and more particularly to an estimation device for a nitrogen compound concentration (hereinafter referred to as engine exhaust NOx concentration) in exhaust gas discharged from an internal combustion engine.

  In order to improve the exhaust emission performance, it is necessary to detect the engine exhaust NOx concentration with high accuracy. The engine exhaust NOx concentration is generally detected by a NOx sensor provided in the exhaust passage upstream of the NOx catalyst. Further, in order to detect the NOx purification rate of the NOx catalyst, it is necessary to provide NOx sensors on the upstream side and the downstream side of the NOx catalyst, respectively.

  However, the NOx sensor has a problem that the NOx concentration cannot be sensed for a predetermined period from the start of the engine to the completion of warm-up. In addition, if NOx sensors are provided upstream and downstream of the NOx catalyst in order to detect the NOx purification rate of the NOx catalyst, there is a problem that the cost increases due to an increase in the number of sensors.

  For this reason, there is a demand for estimating the engine exhaust NOx concentration with high accuracy based on a model formula, a map and the like without using a NOx sensor.

JP 2013-107631 A

  In general, the engine exhaust NOx concentration is estimated based on a map that is referred to based on the engine speed and the fuel injection amount, or a model formula that includes the engine speed and the fuel injection amount as input values. . However, since the actual engine exhaust NOx concentration varies depending on the fuel injection timing, common rail pressure, cooling water temperature, etc., the estimation accuracy cannot be sufficiently ensured by the method of estimating based only on the engine speed and the fuel injection amount. There are challenges.

  The disclosed apparatus aims to effectively improve the estimation accuracy of the engine exhaust NOx concentration.

  The disclosed apparatus is an exhaust gas estimation device that estimates the NOx concentration in exhaust gas discharged from an internal combustion engine, and the exhaust gas discharged from the internal combustion engine based on the rotational speed and fuel injection amount of the internal combustion engine. A reference NOx concentration value calculating means for calculating a reference NOx concentration value in the gas, and multiplying the reference NOx concentration value by a predetermined first correction value set based on a fuel injection timing of the internal combustion engine. Estimated NOx concentration value calculating means for calculating an estimated NOx concentration value in the exhaust gas discharged from the engine.

  The apparatus further comprises common rail pressure detecting means for detecting the pressure of the common rail that supplies the accumulated fuel to the injector of the internal combustion engine, and the estimated NOx concentration value calculating means is detected by the common rail pressure detecting means as the reference NOx concentration value. The estimated NOx concentration value may be calculated by further multiplying a predetermined second correction value set from the common rail pressure.

  Cooling water temperature detecting means for detecting the cooling water temperature flowing through the cooling water circulation path of the internal combustion engine is further provided, and the estimated NOx concentration value calculating means is configured to calculate the reference NOx concentration value from the cooling water temperature detected by the cooling water temperature detecting means. The estimated NOx concentration value may be calculated by further multiplying a predetermined third correction value to be set.

  The disclosed apparatus is an exhaust gas estimation device that estimates the NOx concentration in exhaust gas discharged from an internal combustion engine, and a common rail pressure detection unit that detects a pressure of a common rail that supplies pressure accumulation fuel to an injector of the internal combustion engine. The reference NOx concentration value calculating means for calculating the reference NOx concentration value in the exhaust gas discharged from the internal combustion engine based on the rotational speed and the fuel injection amount of the internal combustion engine, and the common rail pressure detecting means. Estimated NOx concentration value calculating means for calculating an estimated NOx concentration value in exhaust gas discharged from the internal combustion engine by multiplying the reference NOx concentration value by a predetermined second correction value set from a common rail pressure; It may be provided.

  The disclosed apparatus is an exhaust gas estimation device that estimates the NOx concentration in exhaust gas discharged from an internal combustion engine, the cooling water temperature detecting means for detecting the cooling water temperature flowing through the cooling water circulation path of the internal combustion engine, and the internal combustion engine Based on the engine speed and the fuel injection amount, the reference NOx concentration value calculating means for calculating the reference NOx concentration value in the exhaust gas discharged from the internal combustion engine, and the cooling water temperature detected by the cooling water temperature detecting means An estimated NOx concentration value calculating means for calculating an estimated NOx concentration value in the exhaust gas discharged from the internal combustion engine by multiplying the predetermined third correction value to be set by the reference NOx concentration value; Good.

  The apparatus further comprises oxygen concentration acquisition means for acquiring the oxygen concentration in the cylinder of the internal combustion engine, and the estimated NOx concentration value calculation means is set to the reference NOx concentration value from the oxygen concentration acquired by the oxygen concentration acquisition means. The estimated NOx concentration value may be calculated by further multiplying the predetermined fourth correction value.

  Intake air temperature acquisition means for acquiring the intake air temperature sucked into the cylinder of the internal combustion engine is further provided, and the estimated NOx concentration value calculation means is acquired by the intake air temperature acquisition means as the reference NOx concentration value. The estimated NOx concentration value may be calculated by further multiplying a predetermined fifth correction value set from the intake air temperature.

  According to the disclosed apparatus, it is possible to effectively improve the estimation accuracy of the engine exhaust NOx concentration.

1 is a schematic overall configuration diagram showing an intake / exhaust system of an engine to which an exhaust gas estimation device according to an embodiment of the present invention is applied. It is a functional block diagram which shows the exhaust-gas estimation apparatus which concerns on one Embodiment of this invention.

  Hereinafter, an exhaust gas estimation device according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 shows an overall configuration diagram of a diesel engine (hereinafter simply referred to as an engine) 10 to which the exhaust gas estimation device of the present embodiment is applied.

  Each cylinder of the engine 10 is provided with an in-cylinder injector 12 that directly injects high-pressure fuel pressurized by a fuel pump (not shown) and accumulated in the common rail 11 into each cylinder. The fuel injection amount and injection timing of the in-cylinder injector 12 are controlled by an electronic control unit (hereinafter referred to as ECU) 50.

  The common rail 11 is provided with a common rail pressure sensor 40 capable of detecting a common rail pressure corresponding to the fuel injection pressure. The common rail pressure detected by the common rail pressure sensor 40 is input to the electrically connected ECU 50.

  An intake passage 13 is connected to the intake manifold 10A of the engine 10, and an exhaust passage 20 is connected to the exhaust manifold 10B.

  In the intake passage 13, an air cleaner 14, a MAF sensor 41, a compressor 15 </ b> A of the supercharger 15, an intercooler 16, an intake air temperature sensor 46, and the like are provided in order from the intake upstream side. The intake air amount detected by the MAF sensor 41 and the intake air temperature detected by the intake air temperature sensor 46 are respectively input to the electrically connected ECU 50. In the exhaust passage 20, a turbine 15 </ b> B of the supercharger 15, an exhaust aftertreatment device (not shown), and the like are provided in order from the exhaust upstream side.

  The exhaust gas recirculation (EGR) device 30 includes an EGR passage 31 that circulates part of the exhaust gas to the intake system, an EGR cooler 32 that cools EGR gas, and an EGR valve 33 that adjusts the EGR gas flow rate. An EGR gas temperature sensor 42 that detects the temperature of the EGR gas cooled by the EGR cooler 32 is provided in the EGR passage 31 on the downstream side of the EGR cooler 32. The EGR gas temperature detected by the EGR gas temperature sensor 42 is input to the electrically connected ECU 50.

The engine speed sensor 43 detects the speed Ne of a crankshaft (not shown) of the engine 10. The accelerator opening sensor 44 detects an accelerator pedal depression amount corresponding to the fuel injection amount Q of the in-cylinder injector 12. The cooling water temperature sensor 45 detects the temperature T _{clnt of the} cooling water flowing through the engine cooling water circulation path 35, only a part of which is shown in FIG. The sensor values of these sensors 43 to 45 are respectively input to the electrically connected ECU 50.

  The ECU 50 performs various controls of the engine 10 and includes a known CPU, ROM, RAM, input port, output port, and the like. Further, as shown in FIG. 2, the ECU 50 includes a reference NOx concentration value calculation unit 51 and an estimated NOx concentration value calculation unit 52 as some functional elements. In the present embodiment, each of these functional elements is described as being included in the ECU 50 that is integral hardware, but any one of these functional elements may be provided in separate hardware.

The reference NOx concentration value calculation unit 51 calculates a reference NOx concentration value NOx _ref in the exhaust gas exhausted from the engine 10 based on the operating state of the engine 10. More specifically, in the memory of the ECU 50, a reference NOx concentration value map M1 that is referenced based on the engine speed Ne and the fuel injection amount Q is stored in advance. The reference NOx concentration value calculation unit 51 calculates a reference NOx concentration value NOx _ref by reading values corresponding to the sensor values of the engine speed sensor 43 and the accelerator opening sensor 44 from the reference NOx concentration value map M1.

The estimated NOx concentration value calculation unit 52 _adds the oxygen concentration correction value A, the fuel injection timing correction value B, the common rail pressure correction value C, and the cooling water temperature correction to the reference NOx concentration value NOx _ref input from the reference NOx concentration value calculation unit 51. The estimated NOx concentration value NOx _{ENG_out} in the exhaust gas discharged from the engine 10 is calculated based on the following formula (1) that multiplies the value D and the cylinder intake air temperature correction value E.

In Equation (1), O2 _cyl is the current in-cylinder oxygen concentration, O2 _{cyl_ref} is the reference in-cylinder oxygen concentration under standard atmospheric pressure conditions, α _O2 is the oxygen concentration correction index, e is the base of natural logarithm, and θ _soi is the current Fuel injection timing, θ _{soi_ref} is a reference fuel injection timing under standard atmospheric pressure conditions, β _soi is a fuel injection timing correction coefficient, P _rail is a current common rail pressure, P _{rail_ref} is a reference common rail pressure under standard atmospheric pressure conditions, β _rail is the common rail pressure correction coefficient, T _clnt is the current cooling water temperature, T _{clnt_ref} is the reference cooling water temperature under standard atmospheric pressure conditions, β _clnt is the cooling water temperature correction coefficient, and T _inm is the current intake air temperature in the intake manifold 10A (hereinafter referred to as “in air intake manifold 10A”). , that the cylinder intake air _{temperature), T inm_ref} the reference cylinder intake air temperature of the atmospheric conditions alpha _inm denotes the cylinder intake air temperature correction index, respectively. Hereinafter, details of each of these correction values A to E will be described.

[Oxygen concentration correction value]
The oxygen concentration correction value A is the fourth correction value of the present invention, and as shown in the equation (1), a value obtained by dividing the current in-cylinder oxygen concentration O2 _cyl by the reference in-cylinder oxygen concentration O2 _{cyl_ref} is the oxygen concentration. It is calculated by raising the correction index α _{O2 to the} power. The current in-cylinder oxygen concentration O2 _cyl is estimated based on the intake air amount, EGR gas amount, and the like input from various sensors. The reference in-cylinder oxygen concentration O2 _{cyl_ref} is read from a reference oxygen concentration map M2 that is referred to based on the engine speed Ne and the fuel injection amount Q. The oxygen concentration correction index α _O2 is read from an oxygen concentration correction index map M3 that is referred to based on the engine speed Ne and the fuel injection amount Q. The reference oxygen concentration map M2 and the oxygen concentration correction index map M3 are stored in advance in the memory of the ECU 50.

[Fuel injection timing correction value]
The fuel injection timing correction value B is the first correction value of the present invention, and as shown in the mathematical formula (1), the fuel injection timing correction is _performed by subtracting the reference fuel injection timing θ _{soi_ref} from the current fuel injection timing θ _soi. It is calculated by raising the base e of the natural logarithm by the value multiplied by the coefficient β _soi . The current fuel injection timing θ _soi is read from the value indicated to the in-cylinder injector 12. The reference fuel injection timing θ _{soi_ref} is read from a reference injection timing map M4 that is referred to based on the engine speed Ne and the fuel injection amount Q. The fuel injection timing correction coefficient β _soi is read from an injection timing correction coefficient map M5 that is referred to based on the engine speed Ne and the fuel injection amount Q. The reference injection timing map M4 and the injection timing correction coefficient map M5 are stored in advance in the memory of the ECU 50.

[Common rail pressure correction value]
Common rail pressure correction value C is the second correction value of the present invention, as shown in Equation (1), the common rail pressure correction coefficient beta _rail to a value obtained by subtracting the reference rail pressure _{P Rail_ref} the current common rail pressure _{P rail} It is calculated by riding. The current common rail pressure P _rail is read from the sensor value of the common rail pressure sensor 40. The reference common rail pressure P _{rail_ref} is read from a reference common rail pressure map M6 that is referred to based on the engine speed Ne and the fuel injection amount Q. The common rail pressure correction coefficient β _rail is read from the common rail pressure correction coefficient map M7 that is referred to based on the engine speed Ne and the fuel injection amount Q. The reference common rail pressure map M6 and the common rail pressure correction coefficient map M7 are stored in advance in the memory of the ECU 50.

[Cooling water temperature correction value]
The cooling water temperature correction value D is a third correction value of the present invention, and, as shown in Equation (1), the cooling water temperature correction coefficient β _{clnt is obtained} by subtracting the reference cooling water temperature T _{clnt_ref} from the current cooling water temperature T _clnt. It is calculated by riding. The current coolant temperature T _clnt is read from the sensor value of the coolant temperature sensor 45. The reference cooling water temperature T _{clnt_ref} is read from a reference cooling water temperature map M8 that is referred to based on the engine speed Ne and the fuel injection amount Q. The coolant temperature correction coefficient β _clnt is read from the coolant temperature correction coefficient map M9 that is referred to based on the engine speed Ne and the fuel injection amount Q. The reference cooling water temperature map M8 and the cooling water temperature correction coefficient map M9 are stored in advance in the memory of the ECU 50.

[In-cylinder intake air temperature correction value]
The in-cylinder intake air temperature correction value E is the fifth correction value of the present invention, and as shown in Equation (1), the current in-cylinder intake air temperature T _inm is _divided by the reference in-cylinder intake air temperature T _{inm_ref} . This value is calculated by _{raising the} in-cylinder intake air temperature correction index α _{inm to the} power. The current in-cylinder intake air temperature T _inm is estimated based on the intake air temperature, EGR gas temperature, and the like input from various sensors. The reference in-cylinder intake air temperature T _{inm_ref} is read from a reference in-cylinder intake air temperature map M10 that is referred to based on the engine speed Ne and the fuel injection amount Q. The in-cylinder intake air temperature correction index α _inm is read from the in-cylinder intake air temperature correction index map M11 that is referred to based on the engine speed Ne and the fuel injection amount Q. The reference in-cylinder intake air temperature map M10 and the in-cylinder intake air temperature correction index map M11 are stored in advance in the memory of the ECU 50.

As described above in detail, the exhaust gas estimation device of the present embodiment is set to the reference NOx concentration value NOx _ref estimated based on the engine speed Ne and the fuel injection amount Q according to changes in the atmospheric pressure environment. The estimated NOx concentration value NOx is obtained by multiplying the correction values of the oxygen concentration correction value A, fuel injection timing correction value B, common rail pressure correction value C, cooling water temperature correction value D, and cylinder intake air temperature correction value E. It is configured to calculate _{ENG_out} . As a result, the NOx concentration in the exhaust gas discharged from the engine 10 can be estimated with high accuracy without being affected by changes in the atmospheric pressure environment.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, the engine 10 is not limited to a diesel engine, but can be applied to other engines such as a gasoline engine.

DESCRIPTION OF SYMBOLS 10 Engine 11 Common rail 12 In-cylinder injector 13 Intake passage 14 Air cleaner 15 Supercharger 15A Compressor 15B Turbine
16 Intercooler 20 Exhaust passage 30 EGR device 31 EGR passage 32 EGR cooler 33 EGR valve 40 Common rail pressure sensor 41 MAF sensor 42 EGR gas temperature sensor 43 Engine speed sensor 44 Accelerator opening sensor 45 Cooling water temperature sensor 46 Intake temperature sensor 50 ECU
51 Reference NOx Concentration Value Calculation Unit 52 Estimated NOx Concentration Value Calculation Unit

Claims (7)

An exhaust gas estimation device for estimating a NOx concentration in exhaust gas discharged from an internal combustion engine,
Reference NOx concentration value calculating means for calculating a reference NOx concentration value in the exhaust gas discharged from the internal combustion engine based on the rotational speed of the internal combustion engine and the fuel injection amount;
Estimated NOx for calculating an estimated NOx concentration value in the exhaust gas discharged from the internal combustion engine by multiplying the reference NOx concentration value by a predetermined first correction value set based on the fuel injection timing of the internal combustion engine An exhaust gas estimation device comprising: a concentration value calculation means. A common rail pressure detecting means for detecting a pressure of a common rail for supplying pressure accumulation fuel to the injector of the internal combustion engine;
The estimated NOx concentration value calculating means calculates the estimated NOx concentration value by further multiplying the reference NOx concentration value by a predetermined second correction value set from the common rail pressure detected by the common rail pressure detecting means. The exhaust gas estimation device according to claim 1. A cooling water temperature detecting means for detecting a cooling water temperature flowing through the cooling water circulation path of the internal combustion engine;
The estimated NOx concentration value calculating means calculates the estimated NOx concentration value by further multiplying the reference NOx concentration value by a predetermined third correction value set from the cooling water temperature detected by the cooling water temperature detecting means. The exhaust gas estimation device according to claim 1 or 2. An exhaust gas estimation device for estimating a NOx concentration in exhaust gas discharged from an internal combustion engine,
Common rail pressure detecting means for detecting the pressure of the common rail that supplies the pressure-accumulated fuel to the injector of the internal combustion engine;
Reference NOx concentration value calculating means for calculating a reference NOx concentration value in the exhaust gas discharged from the internal combustion engine based on the rotational speed of the internal combustion engine and the fuel injection amount;
An estimated NOx concentration value in the exhaust gas discharged from the internal combustion engine is calculated by multiplying the reference NOx concentration value by a predetermined second correction value set from the common rail pressure detected by the common rail pressure detecting means. An exhaust gas estimation device comprising: estimated NOx concentration value calculation means. An exhaust gas estimation device for estimating a NOx concentration in exhaust gas discharged from an internal combustion engine,
Cooling water temperature detecting means for detecting the temperature of the cooling water flowing through the cooling water circulation path of the internal combustion engine;
Reference NOx concentration value calculating means for calculating a reference NOx concentration value in the exhaust gas discharged from the internal combustion engine based on the rotational speed of the internal combustion engine and the fuel injection amount;
The estimated NOx concentration value in the exhaust gas discharged from the internal combustion engine is calculated by multiplying the reference NOx concentration value by a predetermined third correction value set from the cooling water temperature detected by the cooling water temperature detecting means. An exhaust gas estimation device comprising: estimated NOx concentration value calculation means. Oxygen concentration acquisition means for acquiring the oxygen concentration in the cylinder of the internal combustion engine,
The estimated NOx concentration value calculating means calculates the estimated NOx concentration value by further multiplying the reference NOx concentration value by a predetermined fourth correction value set from the oxygen concentration acquired by the oxygen concentration acquiring means. The exhaust gas estimation device according to any one of claims 1 to 5. An intake air temperature acquisition means for acquiring an intake air temperature sucked into the cylinder of the internal combustion engine;
The estimated NOx concentration value calculation means further multiplies the reference NOx concentration value by a predetermined fifth correction value set from the intake air temperature acquired by the intake air temperature acquisition means, to thereby calculate the estimated NOx concentration value. The exhaust gas estimation device according to any one of claims 1 to 6.

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