JP6938970B2 - Estimator and estimation method - Google Patents

Description

The present invention relates to an estimation device and an estimation method, and more particularly to an estimation of a mass flow rate of a nitrogen compound (hereinafter referred to as NOx mass flow rate) in an engine exhaust passage.

Conventionally, various techniques for estimating the NOx mass flow rate based on the NOx concentration detected by the NOx sensor, the intake air flow rate detected by the intake air flow rate sensor (hereinafter, MAF sensor), and the like have been proposed (for example, Patent Documents). See 1 and 2 etc.).

Japanese Unexamined Patent Publication No. 2016-200111 Japanese Unexamined Patent Publication No. 2009-281952

By the way, when the NOx mass flow rate is estimated using the MAF sensor and the NOx sensor, since the position of the MAF sensor and the position of the NOx sensor are separated, a phase difference occurs between the exhaust gas mass flow rate and the NOx concentration. Therefore, there is a problem that the NOx mass flow rate cannot be estimated accurately. As a result, for example, when controlling the supply amount of urea water to be supplied to the SCR catalyst as a reducing agent based on such an estimated value, the NOx purification rate may decrease due to insufficient supply amount or excessive injection. Ammonia slip may occur.

The technique of the present disclosure aims to effectively improve the estimation accuracy of NOx mass flow rate.

The techniques of the present disclosure include an exhaust gas mass flow rate acquisition means for acquiring the mass flow rate of the exhaust gas discharged from the engine, a nitrogen compound concentration acquisition means for acquiring the nitrogen compound concentration of the exhaust gas, and a mass flow rate of the exhaust gas. The phase correction time setting means for setting the phase correction time for correcting the phase to the phase of the nitrogen compound concentration to the mass flow rate of the exhaust gas, and the exhaust gas whose phase correction time is set by the phase correction time setting means. It is characterized by comprising a nitrogen compound mass flow rate estimating means for estimating the mass flow rate of the nitrogen compound based on the mass flow rate and the nitrogen compound concentration acquired by the nitrogen compound concentration acquiring means.

Further, the exhaust gas mass flow rate acquisition means includes an engine load acquisition unit for acquiring the engine load of the engine and an air flow rate acquisition unit for acquiring the intake air flow rate sucked into the intake passage of the engine. It is preferable to acquire the mass flow rate of the exhaust gas based on the fuel indicated injection amount of the engine and the intake air flow rate according to the engine load.

Further, it is preferable that the phase correction time setting means reduces the phase correction time as the mass flow rate of the exhaust gas increases.

The technique of the present disclosure obtains the mass flow rate of the exhaust gas discharged from the engine and the nitrogen compound concentration of the exhaust gas, and corrects the phase of the mass flow rate of the exhaust gas to the phase of the nitrogen compound concentration. , The mass flow rate of the nitrogen compound is set to the mass flow rate of the exhaust gas, and the mass flow rate of the nitrogen compound is estimated based on the mass flow rate of the exhaust gas and the nitrogen compound concentration for which the phase correction time is set.

According to the technique of the present disclosure, the estimation accuracy of the NOx mass flow rate can be effectively improved.

It is a schematic whole block diagram which shows the intake / exhaust system of the engine which concerns on one Embodiment of this invention. It is a functional block diagram of the estimation apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the map which defines the correlation between the exhaust gas mass flow rate and the phase correction time which concerns on one Embodiment of this invention. It is a figure explaining the operation effect by the estimation apparatus and estimation method which concerns on one Embodiment of this invention. It is a functional block diagram of the estimation apparatus which concerns on other embodiment of this invention.

Hereinafter, an estimation device and an estimation method according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts have the same reference numerals, and their names and functions are also the same. Therefore, detailed explanations about them will not be repeated.

As shown in FIG. 1, the diesel engine (hereinafter, engine) 10 is provided with an intake manifold 11 and an exhaust manifold 12. An intake passage 13 for introducing fresh air is connected to the intake manifold 11, and an exhaust passage 14 for discharging exhaust gas to the atmosphere is connected to the exhaust manifold 12.

The intake passage 13 is provided with an air cleaner 15, a MAF sensor 93, a compressor 22 of the supercharger 20, an intercooler 16, a boost pressure sensor 92, and the like in this order from the intake upstream side. The exhaust passage 14 is provided with a turbine 21, a front-stage post-processing device 40, an exhaust temperature sensor 94, an upstream NOx sensor 95, a post-stage post-processing device 41, a downstream NOx sensor 96, and the like in order from the exhaust upstream side. ing.

The exhaust gas recirculation device (hereinafter, EGR device) 30 includes an EGR passage 31 that connects an exhaust passage 14 on the upstream side of the turbine 21 and an intake passage 13 on the downstream side of the compressor 22, and an EGR cooler that cools the EGR gas. 32 and an EGR valve 33 whose EGR amount can be adjusted are provided.

The pretreatment device 40 includes an oxidation catalyst 42 and a particulate filter (hereinafter, filter) 43 in this order from the upstream side of the exhaust gas.

The oxidation catalyst 42 is formed by supporting an oxidation catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure, and contains carbon monoxide (CO) and hydrocarbons (HC) contained in the exhaust gas. ) Is oxidized. When the unburned HC is supplied by the post injection of the in-cylinder injector or the exhaust pipe injection of the exhaust pipe injector (not shown), the oxidation catalyst 42 oxidizes the HC and raises the exhaust temperature.

The filter 43 is formed, for example, by arranging a large number of cells partitioned by a porous partition wall along the flow direction of exhaust gas, and alternately sealing the upstream side and the downstream side of these cells. .. The filter 43 collects particulate matter (hereinafter referred to as PM) in the exhaust gas in the pores and the surface of the partition wall, and when the PM accumulation amount reaches a predetermined upper threshold value, the filter regeneration is carried out to burn and remove the particulate matter (hereinafter referred to as PM). Will be done.

The post-stage post-treatment device 41 includes a urea water addition device 44 and a selective reduction catalyst (hereinafter, SCR catalyst) 48 in this order from the upstream side of the exhaust gas.

The urea water addition device 44 includes a urea water tank 45 for storing urea water, a urea water pump 46 for pumping urea water from the urea water tank 45, and a urea water addition nozzle 47 for adding urea water into the exhaust passage 14. I have. The urea water injected into the exhaust passage 14 from the urea water addition nozzle 47 is decomposed by the exhaust heat to _{generate ammonia (NH 3} ), which is supplied to the SCR catalyst 48 on the downstream side as a reducing agent.

The SCR catalyst 48 is formed by supporting zeolite or the like on a porous ceramic carrier, for example. _{The SCR catalyst 48 adsorbs NH 3} supplied as a reducing agent from the urea water addition nozzle 47, and selectively reduces and purifies NOx from the exhaust gas passing through the adsorbed NH _3.

The engine speed sensor 90 detects the engine speed Ne from a crankshaft (not shown) of the engine 10. The accelerator opening sensor 91 instructs the fuel instruction injection amount Q of the engine 10 according to the depression amount of the accelerator pedal (not shown).

The boost pressure sensor 92 detects the boost pressure (supercharging pressure) in the intake passage 13. MAF sensor 93 detects an intake air flow rate _{q Air} introduced from the air cleaner 15 into the intake passage 13. The exhaust temperature sensor 94 detects the exhaust temperature of the exhaust gas flowing through the exhaust passage 14 on the upstream side of the SCR catalyst 48.

The upstream NOx sensor 95 and the downstream NOx sensor 96 are, for example, a two-cell type NOx sensor that detects the _{O2 concentration and the NOx concentration NOx_S.} The mounting positions of the exhaust temperature sensor 94, the upstream NOx sensor 95, and the downstream NOx sensor 96 are not limited to the illustrated examples, and may be other parts of the exhaust passage 14. Each of these sensors 90 to 96 is electrically connected to an electronic control unit (hereinafter, ECU) 100.

The ECU 100 controls the engine 10 and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, the sensor values of the sensors 90 to 96 are input to the ECU 100.

Further, as shown in FIG. 2, the ECU 100 includes an exhaust gas mass flow rate calculation unit 110, a phase correction time setting unit 120, a NOx mass flow rate estimation value calculation unit 130, and a coefficient setting unit 140 as some functional elements. Have as. Although each of these functional elements will be described as being included in the ECU 100 which is integrated hardware, any part of them may be provided in separate hardware.

The exhaust gas mass flow rate calculation unit 110 exhausts the exhaust gas discharged from the engine 10 based on the fuel indicated injection amount Q of the engine 10 input from the accelerator opening sensor 91 and the intake air flow rate q _{Air input from the MAF sensor 93.} The mass flow rate of the gas passing through per unit time (hereinafter, exhaust gas mass flow rate _{qm_Ex} ) is calculated. More specifically, the exhaust gas mass flow rate calculation unit 110, by adding calculates the fuel instructed injection amount Q and the intake air flow rate q _Air, computes the exhaust gas mass flow qm _{_ex.}

The phase correction time setting unit 120 corrects the phase of the exhaust gas mass flow rate _{qm_Ex input from the exhaust gas mass flow rate calculation unit 110 to the phase of the upstream NOx concentration NOx_S} input from the upstream NOx sensor 95. (Delay time) T is estimated and set to the exhaust gas mass flow rate _{qm_Ex} . The phase correction time T is the time until the intake air at the position of the MAF sensor 93 flows through the intake passage 13, the engine 10, and the exhaust passage 14 and reaches the upstream NOx sensor 95 as exhaust gas. For example, the exhaust gas mass. It is set according to the flow rate _{qm_Ex.}

More specifically, the memory of the ECU 100 _stores a phase correction time map M1 (see FIG. 3) that defines the correlation between the exhaust gas mass flow rate qm_Ex and the phase correction time T, which is created in advance by experiments or the like. .. In this phase correction time map M1, the phase correction time T is set to decrease as the _{exhaust gas mass flow rate qm_Ex increases.} The phase correction time setting unit 120 reads the phase correction time T corresponding to the exhaust gas mass flow rate qm _{_Ex from the phase correction time map M1 and sets the} phase correction time T to the exhaust gas mass flow rate qm _{_Ex} .

The NOx mass flow rate estimation value calculation unit 130 has a coefficient K input from the coefficient setting unit 140, an upstream NOx concentration _{NOx_S} input from the upstream NOx sensor 95, and a phase correction time T input from the phase correction time setting unit 120. Based on the set exhaust gas mass flow rate _{qm_Ex} (hereinafter, corrected exhaust gas mass flow rate _{qm_Ex_T} ), an estimated value of the mass flow rate of NOx passing per unit time at the position of the upstream NOx sensor 95 (hereinafter, NOx mass). _{Calculate the} estimated flow rate qm _NOx).

More specifically, the coefficient setting unit 140 sets, for example, the NOx weight ratio as a predetermined coefficient K, and outputs the value of the coefficient K to the NOx mass flow rate estimation value calculation unit 130. Then, NOx mass flow estimate calculation unit 130, a coefficient K, the upstream NOx concentration _{NOx _S,} by multiplying operation on the corrected exhaust gas mass flow _{qm _Ex_T,} calculates the NOx mass flow estimate _{qm _NOx.} The coefficient K may be a predetermined fixed value, or may be changed by a map or the like according to the excess air ratio based on the sensor value from the upstream NOx sensor 95.

As described above in detail, according to this embodiment, the fuel instructed injection amount Q and the intake air flow rate q exhaust gas mass flow qm _{_ex} that is calculated based on the _Air By setting the phase correction time T, FIG. 4 The exhaust gas mass flow rate qm _{_Ex} shown by the characteristic line A is corrected to the corrected exhaust gas mass flow rate qm _{_Ex_T shown by the characteristic line B.} Then, the NOx mass flow rate estimated value qm _{_NOx} is calculated _{based on the corrected exhaust gas mass flow rate qm _Ex_T} shown by the characteristic line B and the _{upstream NOx concentration NOx _S} shown by the characteristic line C. _{qm_NOx} can be brought closer to the actual value of the NOx mass flow rate at the position of the upstream NOx sensor 95. Thereby, the estimation accuracy of the NOx mass flow rate can be effectively improved. By improving the accuracy of the NOx mass flow rate, for example, the amount of urea water injected from the urea water addition nozzle 47 can be controlled more accurately, and as a result, the amount of urea water injected is insufficient or excessive. It is possible to effectively prevent a decrease in NOx purification rate and ammonia slip due to injection.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the spirit of the present invention.

For example, as shown in FIG. 5, the ECU 100 partially functions the exhaust gas mass flow rate calculation unit 110, the phase correction time calculation setting unit 150, the NOx mass flow rate estimation value calculation unit 130, and the coefficient setting unit 140. It may have as an element. In this case, the phase correction time calculation setting unit 150 calculates the phase correction time T by dividing the passage volume V from the MAF sensor 93 to the upstream NOx sensor 95 by the exhaust gas volume flow rate _{qv_Ex, and calculates the phase.} The correction time T is set to the exhaust gas mass flow rate _{qm_Ex.} Here, the passage volume V is set in advance as a fixed value according to a design value or the like. Further, the exhaust gas volume flow rate _{qv_Ex is calculated based} on the engine speed Ne, the fuel indicated injection amount Q, the boost pressure input from the boost pressure sensor 92, the exhaust temperature input from the exhaust temperature sensor 94, and the like. As a result, the phase correction time T can be calculated in real time, and the estimation accuracy of the NOx mass flow rate can be effectively improved.

The exhaust gas mass flow qm _{_ex} is not limited to the addition operation of the fuel instructed injection amount Q and the intake air flow rate q _Air, it may be obtained by the exhaust gas flow rate sensor (not shown), various other methods May be obtained by.

Further, the phase correction time T is not limited to the one that corrects the phase of _{the exhaust gas mass flow rate qm _Ex to} the phase of the upstream NOx concentration NOx _{_S , and the phase of the upstream NOx concentration NOx _S is set to} the phase of the exhaust gas mass flow rate qm _{_Ex} . It may be corrected, and both the phase of the upstream NOx concentration NOx _{_S and} the phase of the exhaust gas mass flow rate qm _{_Ex may be corrected to match the phases.}

Further, the NOx mass flow rate estimated value qm _{_NOx} is not limited to the one calculated based on the upstream NOx concentration NOx _{_S} and the corrected exhaust gas mass flow rate qm _{_Ex_T,} but is based on the downstream NOx concentration input from the downstream NOx sensor 96. You may calculate.

Further, the exhaust gas mass flow rate qm _{_Ex} and the upstream NOx concentration NOx _{_S} may be filtered by, for example, removing a noise component by a filter such as a low-pass filter.

Further, the NOx mass flow rate estimated value _{qm_NOx} is not limited to controlling the amount of urea water injected from the urea water addition nozzle 47, and can be used for various other determinations and various controls.

10 Engine 13 Intake passage 14 Exhaust passage 44 Urea water addition device 47 Urea water addition nozzle 48 SCR catalyst 91 Accelerator opening sensor (engine load acquisition means)
93 MAF sensor (air flow rate acquisition means)
95 Upstream NOx sensor (Nitrogen compound concentration acquisition means)
100 ECU
110 Exhaust gas mass flow rate calculation unit (exhaust gas mass flow rate acquisition means)
120 Phase correction time setting unit (Phase correction time setting means)
130 NOx mass flow rate estimation value calculation unit (nitrogen compound mass flow rate estimation means)
140 Coefficient setting unit 150 Phase correction time calculation setting unit (Phase correction time setting means)

Claims (4)

Exhaust gas mass flow rate calculation means for calculating the mass flow rate of engine outlet exhaust gas discharged from the engine,
A nitrogen compound concentration acquisition means for acquiring the nitrogen compound concentration of the downstream exhaust gas flowing downstream of the engine outlet exhaust gas, and
A phase correction time setting means for setting the phase correction time for correcting the phase of the mass flow rate of the engine outlet exhaust gas to the phase of the nitrogen compound concentration to the mass flow rate of the downstream exhaust gas.
Nitrogen compound mass flow rate estimation that estimates the mass flow rate of a nitrogen compound based on the mass flow rate of the exhaust gas whose phase correction time is set by the phase correction time setting means and the nitrogen compound concentration acquired by the nitrogen compound concentration acquisition means. An estimation device characterized by providing means. The exhaust gas mass flow rate calculation means
An engine load acquisition means for acquiring the engine load of the engine and
It is provided with an air flow rate acquisition means for acquiring the intake air flow rate to be sucked into the intake passage of the engine.
The estimation device according to claim 1 , wherein the mass flow rate of the engine outlet exhaust gas is acquired based on the fuel indicated injection amount of the engine and the intake air flow rate according to the engine load. The estimation device according to claim 1 or 2, wherein the phase correction time setting means reduces the phase correction time as the mass flow rate of the engine outlet exhaust gas increases. The mass flow rate of the engine outlet exhaust gas discharged from the engine is calculated, and the nitrogen compound concentration of the downstream exhaust gas flowing downstream of the engine outlet exhaust gas is acquired, and the phase of the mass flow rate of the engine outlet exhaust gas is obtained. The phase correction time for correcting the phase to the nitrogen compound concentration is set to the mass flow rate of the downstream exhaust gas, and the nitrogen is based on the mass flow rate of the exhaust gas for which the phase correction time is set and the nitrogen compound concentration. An estimation method characterized by estimating the mass flow rate of a compound.

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