DE102011089847B4 - Engine control device - Google Patents

Abstract

An engine control device (54) applied to a combustion control system for an internal combustion engine (10) having an external EGR device (48) that is operated such that a portion of an exhaust gas discharged from the engine via an EGR Passage (45, 46) is returned to an intake air passage (12), comprising: an oxygen concentration providing section (B1) for providing an oxygen concentration in an intake gas supplied to the engine (10) and an oxygen concentration in the exhaust gas from the engine (10) by an estimation process; a smoke rise ratio calculating section (B3, B4, B7, B8) for estimating a smoke emission amount in the exhaust gas based on the oxygen concentration in the exhaust gas and calculating a smoke rising rate (ΔPM, Yi) based on a current value of an estimated smoke emission quantity and a reference value for a smoke quantity e in the NOx rising ratio calculating section (B2, B4, B5, B6) for estimating a NOx emission amount in the exhaust gas based on the oxygen concentration in the intake gas and calculating a NOx increase rate (ΔNOx, Xi) from a current value of an estimated NOx emission amount and a reference value for an amount of NOx; andan EGR control section (B9, B10, B11, B12) for controlling an EGR amount by operating the external EGR device (48) based on the smoke rising rate (ΔPM, Yi) and the NOx rising rate (ΔNOx, Xi), wherein said smoke increase ratio calculating section (B3, B4, B7, B8) has a target value setting section (B4) for calculating and setting a smoke target value as a reference value for the smoke amount from an operating state of the engine (10), and said NOx increase ratio calculating section (B2, B4, B5, B6 ) has a target value setting section (B4) for calculating and setting a NOx target value as the reference value for the NOx amount based on the operating state of the engine (10), the smoke increase ratio calculating section (B3, B4, B7, B8) has a calculating section (B8) for the integrated value for calculating an integrated value of the smoke setpoint as well as an integrated value of the estimated smoke emission amount, wherein the Ber In addition, in the integrated value calculating section (B8), calculating a smoke rising ratio (Yi) of the integrated smoke emission amount based on the integrated value of the smoke target, the NOx rising ratio calculating section (B2, B4, B5, B6) calculates an integrated value calculating section (B6) for calculating an integrated value of the NOx target value as well as an integrated value of the estimated NOx emission amount, the integrated value calculating section (B6) further having a NOx increase ratio (Xi) of the integrated value of the estimated NOx emission amount with reference to integrated value of the NOx target value further calculated, and the EGR control section (B9, B10, B11, B12) the target ratio (α0 / β0) of the NOx increase rate (ΔNOx, Xi) with respect to the smoke increase rate (ΔPM, Yi) depending on the smoke rise ratio (Yi) of the integrated value and the NOx increase ratio (Xi) of the integrated value rt.

Description

The present invention relates to an engine control apparatus applied to a combustion control system of an engine having an external EGR apparatus according to which a part of exhaust gas supplied from the engine into an exhaust passage is returned to an intake air passage via an exhaust gas recirculation passage.

A machine control device of this type is known from the prior art, as in the example Japanese Patent No. 3,767,211 (Publication JP 3 767 211 B2 ), according to which a quantity of smoke discharged from a machine is reduced. The smoke is generated shortly after an operating condition of the engine has been changed to an accelerating operating condition due to lack of fresh air in the engine to be fed into the combustion chambers of the engine. In more detail, according to the above-mentioned prior art, an opening degree of an EGR valve provided in the exhaust gas recirculation passage (EGR opening degree) is set in such a manner that an amount of the exhaust gas to be supplied into the intake air passage via the exhaust gas recirculation passage (ie a quantity of external EGR) is reduced.

An EGR opening degree set value is generally adjusted to respective operating states of the engine as a value of an external EGR amount to control a discharge amount of harmful components contained in the exhaust gas (a smoke emission amount, a NOx emission amount, etc.) to a value which is lower than a threshold value in a steady state of an engine operating state corresponding to such an engine operating state in which a sufficient time has elapsed since the control amounts for various actuators for controlling the combustion of the engine have been set to specific values. Therefore, in a transient state in which the engine operating state is changed, an actual external EGR amount may be different from an amount that is provided to an adaptation work. Then, the combustion state may be adversely affected, with the smoke emission amount or the NOx emission amount exceeding the limits.

It is proposed to operate an EGR valve to adjust the external EGR amount in the transient state to avoid the situation described above. When the external EGR amount is increased, the NOx emission amount can be reduced, but the smoke emission amount can be increased as a result of an oxygen concentration in the intake air being reduced. On the other hand, when the external EGR amount is decreased, the smoke emission amount can be reduced, but the NOx emission amount can be increased as a result of the oxygen concentration in the intake air being increased. When such a change of the smoke emission amount and the NOx emission amount with respect to the change of the external EGR amount is taken into consideration, one of the outputs from the smoke emission and the NOx emission may be excessively increased, if the external EGR amount in the transient state is not could be adjusted appropriately. In a case that one of the amounts of the smoke emission amount and the NOx emission amount would become larger than the limit value, it may become difficult to appropriately control the control emission characteristics of the engine.

The publication EP 1 790 840 A1 discloses a controller for an internal combustion engine that operates based on ratios of NOx rise ratios and smoke rise ratios.

The present invention has been made in consideration of the above problems. It is the object of the present invention to provide a machine control apparatus according to which it is possible to appropriately control the emission characteristics of a machine even in a transient state of an engine operating condition.

The object of the invention is achieved by a machine control device according to claim 1. Advantageous embodiments are set forth in the dependent claims.

According to a feature of the present invention, an engine control device ( 54 ) on a combustion control system for an internal combustion engine ( 10 ), which is an external EGR device ( 48 ) which is actuated such that a portion of the exhaust gas discharged from the engine into an intake air passage ( 12 ) via an EGR passage ( 45 . 46 ) is recirculated. The engine control device has an oxygen concentration providing section (FIG. B1 ) to provide an oxygen concentration in an inlet gas to an engine through an estimation process 10 ) and to provide an oxygen concentration in the exhaust gas emitted by the engine ( 10 ) is delivered. The engine control device has a smoke increase rate calculation section (FIG. B3 . B4 . B7 . B8 ) to estimate a smoke emission amount in the exhaust gas based on the oxygen concentration in the exhaust gas, and a smoke increase rate (ΔPM, Yi) based on a current value of an estimated smoke emission amount and a reference value to calculate for a smoke quantity. The engine control apparatus includes a NOx increase rate calculation section (FIG. B2 . B4 . B5 . B6 ) for estimating a NOx emission amount in the exhaust gas based on the oxygen concentration in the intake gas to calculate a NOx increase rate (ΔNOx, Xi) from a current value of an estimated NOx emission amount and a reference value for a NOx amount. And the engine control device has an EGR control section ( B9 . B10 . B11 . B12 ) to increase an amount of EGR by operating the external EGR device ( 48 ) based on the smoke rise rate (ΔPM, Yi) and the NOx increase rate (ΔNOx, Xi).

According to the above-mentioned feature, the external EGR amount is adjusted to control both the smoke rising rate and the NOx rising rate, and these rising rates are input. As a result, the external EGR amount can be controlled by reflecting both the smoke rise rate and the NOx increase rate. Then, it is possible to prevent one of the amounts of the smoke emission amount and the NOx emission amount from excessively increasing, so that the discharge characteristics of the engine can be appropriately controlled.

• 1 eine schematische Ansicht, wie eine Systemstruktur gemäß einer Ausführungsform der vorliegenden Erfindung zeigt;
• 2 ein Diagramm, das einen Anstieg einer Rauchemission bzw. einer NOx-Emission in einem Übergangszustand zeigt;
• 3 ein Diagramm, das eine Anstiegsratenausgleichssteuerung zeigt;
• 4 ein schematisches funktionelles Blockdiagramm, das die Anstiegsratenausgleichssteuerung zeigt; und
• 5 ein Flussdiagramm, das einen Prozess für die Anstiegsratenausgleichssteuerung zeigt.

The above-described and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings shows:

• 1 a schematic view showing how a system structure according to an embodiment of the present invention;
• 2 a diagram showing an increase of a smoke emission and a NOx emission in a transition state;
• 3 a diagram showing a slew rate compensation control;
• 4 a schematic functional block diagram showing the slew rate compensation control; and
• 5 a flowchart showing a process for the slew rate compensation control.

An embodiment of the present invention will be described with reference to the accompanying drawings in which a control apparatus of the present invention is applied to a vehicle having an internal combustion engine with a supercharger (a turbocharger).

1 shows a system structure according to the embodiment of the present invention.

An internal combustion engine 10 shown in the drawing is a type of engine with compression ignition (a diesel engine). An air flow meter 14 for detecting an intake air amount (a fresh air amount), an intercooler 18 to cool the intake air through a turbocharger 16 (explained below) and a throttle valve 20 of which an opening degree by an actuator (an inlet side actuator 20a) , such as a DC motor or the like, are in an intake air passage 12 the machine 10 arranged in this order from a downstream side. The inlet-side actuator 20a also has a function for detecting the opening degree of the throttle valve 20 on.

A storage tank 22 is in the intake air passage 12 on a downstream side of the throttle valve 20 provided. A pressure sensor 24 is in the storage tank 22 for detecting the pressure (charged pressure) through the intake air passage 12 provided streaming inlet air. A temperature sensor 26 is also in the storage tank 22 provided to the temperature of the passage of air through the inlet 12 to detect flowing intake air. A downstream side of the storage tank 22 is with each combustion chamber 28 of corresponding cylinders of the machine 10 connected.

A fuel injector 30 an electromagnetic type is in the combustion chamber 28 the corresponding cylinder of the machine 10 provided in such a manner that a front end thereof into the combustion chamber 28 protrudes. A high-pressure fuel (diesel) is so from a busbar (common rail) (not shown) in the fuel injection valve 30 supplied to the high-pressure fuel from the fuel injection valve 30 into the combustion chamber 28 is injected.

Each opening of an inlet opening and an outlet opening of the corresponding cylinder is passed through each inlet valve 32 or exhaust valve 34 opened and closed. When the inlet valve 32 is opened, which is through the intercooler 18 cooled intake air so into the combustion chamber 28 supplied to this intake air and that of the fuel injection valve 30 injected fuel are exposed to combustion. The air and the fuel that has been exposed to the combustion, as exhaust gas in an exhaust passage 36 delivered when the exhaust valve 34 is open. A crank angle sensor 40 is at a position adjacent to an output shaft (a crankshaft 38 ) the machine 10 provided to a rotation angle of the crankshaft 38 capture.

The turbocharger 16 is between the intake air passage 12 and the exhaust passage 36 provided. The turbocharger 16 is from an intake air compressor 16a passing through the intake air 12 is provided, an exhaust gas turbine 16b passing in the exhaust passage 36 is provided, and a rotating shaft 16c for interconnecting the compressor 16a and the turbine 16b built up. In more detail, the exhaust gas turbine 16b through energy through the exhaust passage 36 flowing exhaust gas is rotated, and a rotational energy is transmitted through the rotary shaft 16c to the intake air compressor 16a transferred, so that the intake air through the intake air compressor 16a is compressed. In other words, the intake air is through the turbocharger 16 charged. According to the present invention, the boost pressure through the turbocharger 16 be adjustable. Namely, when an opening degree in the variable vane (not shown) of the turbocharger 16 is controlled, the boost pressure can be adjusted.

An emission control device 42 and an A / F sensor 44 (Air-fuel sensor) for detecting the oxygen concentration in the exhaust gas are respectively in this order on a downstream side of the turbocharger 16 in the exhaust passage 36 provided. According to the present embodiment, a DPF (Diesel Particulate Filter) for trapping PM (particulate matter = smoke) in the exhaust gas, a NOx catalyst for purifying NOx in the exhaust gas, an oxygen catalyst for purifying HC and CO in the exhaust gas or the like as an exhaust gas purifying apparatus 42 be used.

Part of the exhaust passage 36 discharged exhaust gas is with an exhaust gas recirculation passage such as a high-pressure EGR passage 45 and a low pressure EGR passage 46 back into the intake air passage 12 fed. In more detail, the exhaust passage 36 an upstream side of the exhaust gas turbine 16b via the high pressure EGR passage 45 operationally with the intake air passage 12 a downstream side of the throttle valve 20 (ie, the settlement tank 22 ) connected. An EGR valve 48 is in the high pressure EGR passage 45 provided to adapt to a passage area thereof. The EGR valve 48 is an electronically controlled valve, of which an opening degree (an EGR opening degree) by an actuator (an EGR actuator 48a) such as a DC motor or the like can be controlled. Part of the exhaust passage 36 discharged exhaust gas is dependent on the opening degree of the EGR valve 48 as external EGR back into the intake air passage 12 fed after the exhaust gas through an EGR cooler 50 was cooled. The EGR actuator 48a also has a function for detecting the EGR opening degree.

The exhaust gas passage 36 a downstream side of the exhaust gas turbine 16b is on an upstream side of the intake air compressor 16 via the low pressure EGR passage 46 with the inlet passage 12 connected. An exhaust throttle valve 52 is in the exhaust passage 36 on a downstream side of a branch portion of the low pressure EGR passage 46 provided (at which the passage 46 from the passage 36 is branched off). The exhaust throttle valve 52 is an electronically controlled valve, of which an opening degree by an actuator (an exhaust side actuator 52a) such as a DC motor or the like is controlled. Part of the exhaust passage 36 discharged exhaust gas is also returned to the intake passage as an external EGR depending on an opening degree of a low-pressure side EGR valve (not shown) 12 after the exhaust gas has been cooled by a low-pressure side EGR cooler (not shown). The exhaust side actuator 52a also has a function for detecting the opening degree of the exhaust-side throttle valve 52 on.

An electronic control unit (ECU 54 ) for controlling a machine system is constructed of a microcomputer having a well-known CPU, a ROM, a RAM, etc. An output signal from an acceleration sensor 56 for detecting an operation stroke amount of an accelerator pedal (a pedal step size) by a vehicle driver as well as other output signals from the air flow meter 14 , the pressure sensor 24 , the temperature sensor 26 , the crank angle sensor 40 , the A / F sensor 44 , the inlet-side actuator 20a , the EGR actuator 48a , the exhaust gas actuator 52a be in the ECU 54 entered. The ECU 54 In accordance with the input signals from the respective sensors, various kinds of control programs stored in the ROM execute combustion control of the engine 10 including fuel injection control by the fuel injection valve 30 , an exhaust gas recirculation control (an external EGR control) by the EGR actuator 48a and the like, a boost pressure control by the turbocharger 16 etc. to perform.

The fuel injection control will be explained. A requested moment for the machine 10 is first determined according to an engine speed from the outputs of the crank angle sensor 40 and the operation stroke amount of the accelerator pedal (the pedal step size) from the outputs of the acceleration sensor 56 calculated. An instruction value for the fuel injection valve 30 is calculated based on the above-calculated requested torque for the engine so that a power supply to the fuel injection valve 30 starting from the Instruction value is controlled. As a result, fuel is injected from the fuel injection valve having an amount corresponding to the above-described instruction value.

In the boost pressure control becomes a power supply to the turbocharger 16 controlled so that a boost pressure from the output from the pressure sensor 24 is controlled so that it is closer to a target value.

In the external EGR control, the power supply to the EGR actuator 48a so controlled that the EGR opening degree from the output from the EGR actuator 48a is controlled to be closer to a target value (an EGR target opening degree).

The EGR target opening degree is set in advance by experiments, for example (adjusted). The external EGR is executed according to the target EGR opening degree such that a quantity of the smoke as well as an amount of NOx discharged from the engine 10 in such an engine operating condition (a steady state) are correspondingly smaller than threshold values in which a sufficient amount of time has elapsed since control quantities of the respective combustion control actuators have been set.

In more detail, a smoke emission set value (a smoke set point) set to a value lower than a predetermined smoke emission limit value (a smoke limit value) and a NOx emission setpoint value (a NOx set value) are set. set as a value lower than its predetermined limit value for NOx emission (a NOx limit value) for respective engine speeds and a requested torque of the engine (or a fuel injection amount from the fuel injection valve 30 ), which are parameters indicative of the machine operating condition and distributed. And such EGR opening degree is determined as the EGR target opening degree, according to which each of the current values for the smoke emission and the NOx emission are controlled to be closer to the smoke target value and the NOx target value, although the engine speed and the requested one Machine torque are distributed.

The smoke limit as well as the NOx limit may be set to meet emission characteristics required in a predetermined mode (eg, NEDC mode, LA # 4 mode, and the like) in which fuel consumption ratio, emission, etc. be measured. More specifically, the smoke limit as well as the NOx limit may be used for corresponding engine operating conditions of the engine 10 be set so that a total value of the smoke emission as well as a total value of the NOx emission covering the entire operation mode is made smaller than a required value (a value that satisfies the control for emission). According to the present embodiment, each of the smoke limit and NOx limit values is set as the value of the exhaust gas that permeates the exhaust gas passage 36 on an upstream side of the exhaust gas purifier 42 located.

It is possible to achieve the actual amount of external EGR that is substantially equal to a value that is assumed to set the EGR target opening degree when the actual EGR opening degree is controlled to the target EGR opening degree. However, the actual amount of external EGR in a transient state in which a sufficient time for controlling the actual EGR opening degree to the target EGR opening degree has not elapsed may vary from the amount of external EGR assumed to be Specifies EGR target opening degree. When the actual amount of external EGR varies from the target value, an amount of the intake gas (ie, a mixture of the fresh air and the EGR gas) may be added to the engine 10 the oxygen concentration in the exhaust gas as well as the oxygen concentration in the inlet gas vary from such values to realize the desired combustion. Then, the smoke emission may be increased to become larger than the smoke limit, or the NOx emission may be increased to become larger than the NOx limit.

For example, when the EGR opening degree is changed, the amount of external EGR is changed. Namely, when the EGR opening degree is increased, the amount of external EGR is increased, thereby reducing the oxygen concentration in the intake gas. Then, the NOx emission is reduced while the smoke emission can be increased. On the other hand, when the EGR opening degree is decreased, the amount of external EGR is reduced, thereby increasing the oxygen concentration in the intake gas. Then, the smoke emission is reduced while the NOx emission can be increased. Excursions of the smoke emission and the NOx emission with respect to the change of the EGR opening degree are indicated by a solid line (a compensation line) A in FIG 2 designated. The smoke emission and the NOx emission may become larger than the corresponding limit values in the transient state.

In addition, when the fuel injection amount from the fuel injection valve 30 is changed, the oxygen concentration in the exhaust gas changed. A certain time (a return delay time) is necessary from a time point when the fuel injection amount is changed to a timing at which a part of the exhaust gas into the combustion chamber 28 as the EGR is supplied (the oxygen concentration thereof has been changed by such fuel injection). As a result, the smoke emission and the NOx emission may become larger than the threshold values. When the opening degree of the throttle valve 20 is changed, the intake air amount is also changed.

In particular, when the vehicle is accelerated, the smoke emission or the like may remarkably become larger than the limit value. Namely, the fuel injection amount is increased in accordance with the increase of the engine requested torque during the acceleration of the vehicle. However, there is a time delay (a charge delay) from a point in time when the intake air through the turbocharger 16 is charged until a moment when the charged intake air into the combustion chamber 28 is supplied. Therefore, the intake air amount (the fresh air) is too short for the increased fuel injection amount. As a result, the smoke emission can be greatly increased above the limit, as in 2 by B (denoted by a "Δ").

According to the present embodiment, in order to solve the problem described above (the excessive increase of smoke and / or NOx), a smoke rise ratio (a smoke emission ratio with respect to the smoke target value) and a NOx increase ratio (a NOx emission ratio) with reference to the NOx setpoint) into the ECU 54 is input to perform a rising-ratio equalization control when the EGR opening degree is controlled. How out 3 can be seen (denoted by "□"), according to the compensation control of the present invention, any increase in smoke emission and NOx emission above the corresponding limit value during the transient state is tolerated to a certain extent, but such a situation in which one of the emissions Smoke emission and NOx emission may be excessively increased above the corresponding limit can be avoided. As a result, both the smoke emission and the NOx emission are suppressed to be greatly increased over the limit.

The rise ratio equalization control will be described with reference to FIG 4 explained.

4 FIG. 12 is a schematic functional block diagram showing a process for a slope ratio compensation control according to the present embodiment. FIG.

An oxygen concentration estimation section B1 estimates starting from a boost pressure " P ", An intake air temperature" tmp ", Starting from the output of the temperature sensor 26 , a fresh air amount "air" from the output of the air flow meter 14 , a fuel injection amount " Q "(Or the moment required by the machine" Trq ") From the fuel injector 30 the oxygen concentration in the inlet gas (the inlet gas oxygen concentration) entering the combustion chamber 28 and the oxygen concentration in the exhaust gas (the exhaust gas oxygen concentration) coming from the combustion chamber 28 is delivered. According to the present embodiment, the estimating section estimates B1 from time to time the intake gas oxygen concentration and the exhaust oxygen concentration through a predetermined model for estimating the oxygen concentration.

More specifically, the intake-gas oxygen concentration and the exhaust-gas oxygen concentration are estimated from the following processes. As a first process, the amount of intake gas entering the combustion chamber 28 is to be supplied, starting from the inputs of the boost pressure " P "And the intake air temperature" Tmp "estimated. As a second process, the amount of external EGR passing from the high pressure EGR passage 54 and the low pressure EGR passage 46 in the intake air passage 12 flows calculated based on the estimated intake gas amount as well as the fresh air amount "air". As a third process, the exhaust gas oxygen concentration is estimated based on the amount of fresh air "air" entering the combustion chamber 28 is supplied to the amount of external EGR and the fuel injection amount. " Q "(Or the moment requested for the machine" Trq ") From the fuel injector 30 , According to the above processes, it is possible to estimate from time to time the intake-gas oxygen concentration and the exhaust-gas oxygen concentration while being influenced by that from the combustion chamber 28 discharged and partly into the intake air passage 12 via the high pressure EGR passage 45 and the low pressure EGR passage 46 pushed back exhaust gas is considered.

A learning process may be performed to reduce a variation (a model error) between the estimated oxygen concentration and the actual oxygen concentration. The learning process can be based on the actual oxygen concentration from the output of the AF sensor 44 be executed. The learning process may be preferably performed when a variation of the oxygen concentration between an upstream side and a downstream side of the exhaust gas purifying apparatus 42 is small.

An NOx emission estimation section B2 calculated from the intake gas oxygen concentration, the engine speed " NG "And the moment requested by the machine" Trq "(Or the fuel injection amount" Q From the fuel injector 30 ) an estimate of the NOx emission (an estimated NOx value). Since the NOx emission is increased as the intake gas oxygen concentration becomes higher, the intake gas oxygen concentration is included in any of the parameters in the above calculation of the estimated NOx value. In addition, the NOx emission due to the combustion temperature in the corresponding operating conditions of the machine 10 is affected, and the combustion temperature with the engine speed " NE "And the moment requested by the machine" Trq Can be correlated (which are both parameters that designate the machine operating conditions), also the engine speed " NE "And the moment requested by the machine" Trq In the parameters in the above-described calculation for the estimated NOx value. For example, the estimated NOx value may be calculated using a map or mathematical formula where the estimated NOx value is the intake gas oxygen concentration, the engine speed. NE "And the moment requested by the machine" Trq "Is correlated.

A smoke emission estimation section B3 calculates an estimated smoke emission value (an estimated smoke value) based on the exhaust oxygen concentration, the engine speed " NE "And the moment requested by the machine" Trq "(Or the fuel injection amount" Q From the fuel injector 30 ). Since the smoke emission is increased as the exhaust gas oxygen concentration becomes smaller, the exhaust gas oxygen concentration is included in one of the parameters in the above calculation of the estimated smoke value. In the same way, the engine speed " NE "And the moment requested by the machine" Trq With regard to the NOx emission estimation section B2 Also included in the parameters in the above-described calculation of the estimated smoke value, since the smoke emission by the combustion temperature in the corresponding operating conditions of the machine 10 is affected. For example, the estimated smoke value may be calculated using a map or mathematical formula, where the estimated smoke value is the exhaust oxygen concentration, the engine speed. " NE "And the moment requested by the machine" Trq "Is correlated.

A set point setting section B4 sets a NOx setpoint and smoke setpoint based on engine speed " NE "And the moment requested by the machine" Trq " on.

A first NOx rising ratio calculating section B5 calculates a first NOx increase ratio "ΔNOx" (an immediate value) by dividing each estimated NOx value by each NOx target value. A second NOx rising ratio calculating section B6 calculates a second NOx increase ratio "Xi" (an integrated value) by dividing each integrated value of the estimated NOx value by each integrated value of the NOx target value.

A first smoke rise ratio calculating section B7 calculates a first smoke rise ratio "ΔPM" (an immediate value) by dividing each estimated smoke value by each smoke setpoint. A second smoke rise ratio calculating section B8 calculates a second smoke rise ratio "Yi" (an integrated value) by dividing each integrated value of the estimated smoke value by each integrated value of the smoke setpoint.

A parameter calculation section B9 calculates a control amount (a control parameter "δ") for the increase ratio compensation control. According to the present embodiment, a target ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" is expressed as "α0 / β0", each of the coefficients "α0" and "β0" being greater than zero (α0, β0> 0) and a formula "α0 + β0 = 1".

$$"\mathrm{\alpha }=\left(\mathrm{\alpha }{0}^2\times \mathrm{\beta }\text{i}\right)/\left(\mathrm{\alpha }{0}^2\times \mathrm{\beta }\text{i}+\mathrm{\beta }{0}^2\times \mathrm{\alpha }\text{i}\right)"$$

$$"\mathrm{\beta }=\left(\mathrm{\beta }{0}^2\times \mathrm{\alpha }\text{i}\right)/\left(\mathrm{\alpha }{0}^2\times \mathrm{\beta }\text{i}+\mathrm{\beta }{0}^2\times \mathrm{\alpha }\text{i}\right)"$$

worin $$\mathrm{\alpha }\text{i}=\text{Xi/}\left(\text{Xi+Yi}\right)$$

$$\mathrm{\beta }\text{i}=\text{Xi/}\left(\text{Xi+Yi}\right)$$

The control parameter "δ" is calculated according to a following equation (c1) using the control coefficients "α" and "β" (α, β> 0) so that an actual ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio " ΔPM "is controlled to the desired ratio" α0 / β0 ": $$"\mathrm{\delta }=\mathrm{\beta }\times \left(\Delta \text{NOX}\right)-\mathrm{\alpha }\times \left(\mathrm{\Delta }\text{PM}\right)"$$

$$"\mathrm{\alpha }=\left(\mathrm{<figure-callout\; id="0"\; label="\alpha "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{0}^2\times \mathrm{\beta }\text{i}\right)/\left(\mathrm{<figure-callout\; id="0"\; label="\alpha "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{0}^2\times \mathrm{\beta }\text{i}+\mathrm{<figure-callout\; id="0"\; label="\beta "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\beta </figure-callout>}{0}^2\times \mathrm{\alpha }\text{i}\right)"$$

$$"\mathrm{\beta }=\left(\mathrm{<figure-callout\; id="0"\; label="\beta "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\beta </figure-callout>}{0}^2\times \mathrm{\alpha }\text{i}\right)/\left(\mathrm{<figure-callout\; id="0"\; label="\alpha "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\alpha </figure-callout>}{0}^2\times \mathrm{\beta }\text{i}+\mathrm{<figure-callout\; id="0"\; label="\beta "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\beta </figure-callout>}{0}^2\times \mathrm{\alpha }\text{i}\right)"$$

wherein $$\mathrm{\alpha }\text{i}=\text{Xi /}\left(\text{Xi + Yi}\right)$$

$$\mathrm{\beta }\text{i}=\text{Xi /}\left(\text{Xi + Yi}\right)$$

A technical meaning of the control method for using the above equation (c1) will be explained.

In the above equations, each of the coefficients "ai" and "ßi" is defined by using the integrated-value NOx increase ratio "Xi" and the integrated-value smoke rise ratio "Yi", the NOx rising ratio "Xi" and the smoke rising ratio " Yi "reflect each of the NOx rise ratio" ΔNOx "and the smoke rise ratio" ΔPM ".

According to the above equations (c2) and (c3), in a case where a ratio of the NOx increase ratio "Xi" (the integrated value) with respect to the smoke increase ratio "Yi" (the integrated value) becomes the target value "α0 / β0 ", each of the coefficients" ai "and" βi "becomes" α0 "and" β0 ", respectively. Then, each of the control coefficients "α" and "β" becomes "α0" and "β0", respectively.

A reason for using the control coefficients "α" and "β" instead of the coefficients "α0" and "β0" is to prevent the ratio of the NOx increase ratio "ΔNOx" from the smoke increase ratio "ΔPM" in the case of a longer time scale is greatly shifted from the target ratio "α0 / β0". The longer time scale corresponds e.g. not a case of a microscopic time scale in which the instantaneous values are calculated, but a case in which the entire calculation of the smoke increase ratio "Yi" is carried out, and a time scale is much longer than the microscopic scale.

In the above equation (c1), when "α" and "β" are fixed to "α0" and "β0", and the control parameter "δ" is set to zero "0" by a control, it is possible such a situation in which one of the emissions from the smoke emission and the NOx emission is remarkably increased. Even if the ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" in the microscopic time scale is brought to the target ratio "α0 / β0" by the control, the ratio of the NOx increase ratio "ΔNOx" can be referenced with reference to FIG the smoke rise ratio "ΔPM" in the longer time scale is greatly shifted from the target ratio "α0 / β0". This is because one of the rise ratios may become greater than the other increase ratio, which may depend on driver behavior for vehicle travel, operational delay of various types of combustion control actuators, and so on.

On the other hand, when the control coefficients "α" and "β" are defined as equations (c2) and (c3), in other words, when a target ratio "α / β" for the control coefficients in each control cycle starts from the smoke rise ratio "Yi For the integrated value and the NOx increase ratio "Xi" for the integrated value, the ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" may be reduced to the target ratio "α0 / β0 last in the longer time scale " to be brought.

When the ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" tends to become smaller than the target ratio "α0 / β0" in the longer time scale, the ratio of the coefficient "ai" with respect to the coefficient becomes "Βi" is smaller than the target ratio "α0 / β0", and thereby the control coefficient "α" becomes larger than the coefficient "α0", while the control coefficient "β" becomes smaller than the coefficient "β0". As a result, the increase of the NOx increase ratio "ΔNOx" is allowed while the increase of the smoke increase ratio "ΔPM" is limited.

On the other hand, if that Ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" tends to become larger than the target ratio "α0 / β0" in the longer time scale, the ratio of the coefficient "ai" with respect to the coefficient "βi Becomes larger than the target ratio "α0 / β0", and thereby the control coefficient "α" becomes smaller than the coefficient "α0", while the control coefficient "β" becomes larger than the coefficient "β0". As a result, the increase of the NOx increase ratio "ΔNOx" is limited, while the increase of the smoke increase ratio "ΔPM" is allowed.

The above equations (c2) and (c3) are standardized so that a sum of the control coefficients "α" and "β" becomes a predetermined value "1" when the control coefficients "α" and "β" are calculated. This is to avoid a situation in which a proportional factor "Kp" and an integral factor "Ki" in each control cycle in a control section B10 (explained below) according to the NOx increase ratio "ΔNOx" and the smoke increase ratio "ΔPM" are changed. In other words, even in a case where the NOx increase ratio "ΔNOx" and the smoke rise ratio "ΔPM" are equal to each other, but when the absolute figures of these rise ratios are different from each other, the values for the control parameter "δ" (i.e. is required to make the ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" to the target ratio "α0 / β0" different from each other. In such a case, it is necessary to adjust the proportional factor "Kp" and the integral factor "Ki" to the NOx increase ratio "ΔNOx" and the smoke increase ratio "ΔPM". However, according to the present embodiment, for the purpose of simplifying the adaptability work for the proportional factor "Kp" and the integral factor "Ki", the control coefficients "α" and "β" are standardized in each control cycle to avoid the situation that the proportional factor "Kp" and the integral factor "Ki" in each control cycle is changed depending on the NOx rising ratio "ΔNOx" and the smoke rising ratio "ΔPM".

The regulatory section B10 calculates a control variable (feedback control variable) for the EGR actuator based on the control parameter "δ" 48a , According to the present embodiment, the control amount is calculated by a proportional-integral control based on the control parameter "δ". More specifically, the control quantity is obtained as the sum of a proportional portion obtained by multiplying the control parameter "δ" by the proportional factor "Kp" and an integral portion which is the accumulated magnitude of a value obtained by multiplying the control parameter "δ" by the integral factor. " Ki "is calculated.

A feedforward control section B11 calculates a feedforward control amount (the EGR target opening degree) for the EGR actuator 48a based on the engine speed " NE "And the machine requested moment" Trq ".

An addition section B12 calculates a final operating quantity for the EGR actuator 48a by adding the control amount and the feedforward control amount to each other.

When the power supply to the EGR actuator 48a is controlled based on the final operation amount, the actual EGR opening degree is controlled to such a position that the ratio of the NOx increase ratio "ΔNOx" with respect to the smoke rise ratio "ΔPM" is brought to the target ratio "α0 / β0".

5 FIG. 10 is a flowchart showing a process for the slope ratio compensation control. FIG. The process is done by the ECU 54 executed in a predetermined control cycle.

At one step S10 leads the ECU 54 a process to estimate the intake air oxygen concentration and the exhaust gas oxygen concentration.

At one step S12 leads the ECU 54 a process to calculate the estimated NOx value and the estimated smoke value. At one step S14 leads the ECU 54 a process to set the NOx setpoint and the smoke setpoint.

At one step S16 leads the ECU 54 a process of calculating the NOx rising ratio "ΔNOx", the integrated-value NOx rising ratio "Xi", the smoke rising ratio "ΔPM" and the integrated-value smoke rising ratio "Yi". The ECU 54 may additionally perform such a process according to which the NOx increase ratio "Xi" as well as the smoke increase ratio "Yi" is initialized for a predetermined period of time.

At one step S18 leads the ECU 54 a process of calculating the control parameter "δ" based on the NOx increase ratio "ΔNOx" and the smoke increase ratio "ΔPM". And at a step S20 leads the ECU 54 a process, the power supply to the EGR actuator 48a based on the sum of the control variable and the feedforward control variable.

When the step S20 is completed, the process goes on 5 to an end.

1. (1) Die Leistungszufuhr zu dem EGR-Stellglied 48a wird ausgehend von dem zusätzlichen Wert der Regelungsgröße gesteuert, der ausgehend von dem Steuerparameter „δ“ und der Vorkopplungssteuergröße berechnet wird. Als Ergebnis ist es sogar in dem Übergangszustand des Betriebszustands der Maschine 10 möglich, eine derartige Situation zu vermeiden, dass jede der Emissionen aus der Rauchemission und der NOx-Emission übermäßig erhöht wird. Mit anderen Worten ist es möglich, bevorzugt eine derartige Situation zu vermeiden, dass die Rauchemission höher werden kann als der Rauchgrenzwert, oder dass die NOx-Emission höher werden kann als der NOx-Grenzwert. Da außerdem die externe EGR-Steuerung ausgehend von dem einzelnen Steuerparameter „δ“ ausgeführt wird, ist es ebenfalls möglich die externe EGR-Steuerung einfach und geeignet auszuführen, um das übermäßige Ansteigen der Rauchemission oder der NOx-Emission zu vermeiden.
2. (2) Die Steuerkoeffizienten „α“ und „β“, die zum Berechnen des Steuerparameters „δ“ verwendet werden, werden unter Verwendung des NOx-Anstiegsverhältnisses „Xi“ des integrierten Werts und des Rauchanstiegsverhältnisses „Yi“ des integrierten Werts berechnet, so dass das Verhältnis des NOx-Anstiegsverhältnisses „Xi“ des integrierten Werts mit Bezug auf das Rauchanstiegsverhältnis „Yi“ des integrierten Werts auf das Sollverhältnis „α0/β0“ gesteuert wird. Als Ergebnis ist es möglich, nicht nur die externe EGR-Steuerung durch das Reflektieren des Verhaltens des Fahrers für die Fahrzeugfahrt auszuführen, sondern auch die Emissionscharakteristik in der Maschine 10 geeignet zu steuern, damit sie die Regelanforderungen für die Emission erfüllen.

According to the present embodiment, the following advantages can be obtained.

1. (1) The power supply to the EGR actuator 48a is controlled on the basis of the additional value of the control quantity, which is calculated on the basis of the control parameter "δ" and the feedforward control variable. As a result, it is even in the transient state of the operating state of the engine 10 it is possible to avoid such a situation that each of the emissions from the smoke emission and the NOx emission is excessively increased. In other words, it is possible to preferably avoid such a situation that the smoke emission may become higher than the smoke limit, or that the NOx emission may become higher than the NOx limit. In addition, since the external EGR control is executed from the single control parameter "δ", it is also possible to easily and appropriately perform the external EGR control to avoid the excessive increase of the smoke emission or the NOx emission.
2. (2) The control coefficients "α" and "β" used to calculate the control parameter "δ" are calculated using the NOx rising ratio "Xi" of the integrated one And the smoke rise ratio "Yi" of the integrated value so that the ratio of the NOx increase ratio "Xi" of the integrated value with the smoke increase ratio "Yi" of the integrated value is controlled to the target ratio "α0 / β0". As a result, it is possible to perform not only the external EGR control by reflecting the driver's behavior for the vehicle travel, but also the emission characteristic in the engine 10 suitable to meet the regulatory requirements for emission.

(Modifications)

The above-described embodiment may be modified in the following ways.

(M-1) A method for quantifying increase rates (such as the NOx increase ratio "ΔNOx" and the smoke increase ratio "ΔPM") should not be limited to the method of the above-described embodiment. For example, the slew rates can be calculated in the following ways. The rate of increase for the NOx may be defined as a value calculated by subtracting the estimated NOx value from the NOx setpoint. Similarly, the rate of increase for the smoke may be defined as a value calculated by subtracting the estimated smoke value from the desired smoke value. In this case, the external EGR amount is controlled so that each of the current values for the respective increase rates can be controlled to be smaller than a predetermined value.

In addition, a reference value used when quantifying the increase rates for the NOx and the smoke need not be limited to the above-described target value (the NOx target value, the smoke target value). If e.g. the reference value is defined as zero, both the NOx increase rate and the smoke increase rate correspond to the estimated NOx value and the estimated smoke value. Therefore, the external EGR amount may be performed so that a value calculated by dividing the estimated NOx value by the estimated smoke value may be controlled to be a target value.

In addition, the NOx rate of increase and the smoke rate can be quantified as follows:

An exhaust gas oxygen concentration setpoint and an intake gas oxygen concentration setpoint according to which the smoke emission and the NOx emission are respectively controlled to be lower than the thresholds are set correspondingly for each operating state of the engine. The smoke rise rate may be defined as a variation between an estimated value and the target exhaust gas oxygen concentration, while the NOx increase rate may be defined as a variation between an estimated value and the intake gas oxygen concentration setpoint. A method for adjusting the external EGR amount will be further explained when the above slew rates are used as input information. The NOx increase rate is calculated by subtracting the intake gas oxygen concentration setpoint from the estimated intake oxygen concentration value while calculating the smoke increase rate by subtracting the exhaust oxygen concentration setpoint from the estimated exhaust oxygen concentration value. Then, the external EGR amount is adjusted so that a ratio of these increase rates will be a target ratio.

(M-2) According to the above embodiment, the actual values for the smoke emission and the NOx emission are respectively determined by the smoke emission estimation section B3 and the NOx emission estimation section B2 valued.

However, sensors may be in the exhaust passage 36 between the machine 10 and the emission control device 42 be provided to detect the smoke emission and the NOx emission accordingly.

(M-3) According to the above embodiment, each of the concentrations of the intake gas oxygen concentration and the exhaust oxygen concentration is determined by the oxygen concentration estimation section (FIG. B1 ) valued. However, a sensor (an A / F sensor) for detecting the intake gas oxygen concentration and the exhaust oxygen concentration may be provided.

(M-4) According to the above embodiment, the external EGR amount is controlled by controlling the opening degree of the EGR valve 48 customized. However, the external EGR amount may be controlled by controlling the opening degree of the throttle valve 20 by controlling the power supply to the actuator 20a be adjusted. In such a process, the pressure in the storage tank becomes 22 be reduced, since the opening degree of the throttle valve 20 gets smaller. Because of this, the external EGR amount becomes the intake air passage 12 via the high pressure EGR passage 45 greater. Alternatively, the external EGR amount may be controlled by controlling the opening degree of the exhaust throttle valve 52 by controlling the power supply to the exhaust side actuator 52a be adjusted. In this process, the pressure in the exhaust passage 36 on the upstream side of the exhaust throttle valve 52 increases, since the opening degree of the exhaust throttle valve 52 gets smaller. Because of this, the external EGR amount becomes the intake air passage 12 via the low pressure EGR passage 46 greater.

(M-5) A method of setting the thresholds need not be limited to that of the above embodiment. In a case of appropriately setting the smoke emission limit and NOx emission limits on the downstream side of the exhaust gas purifying apparatus 42 Each of the limits can be set to a smaller value because a degree of purification by the exhaust gas purifier 42 becomes larger for the smoke and the NOx.

(M-6) A method of calculating the control parameter "δ" need not be limited to that of the above embodiment. For example, the control parameter "δ" may be calculated by the following equation (c4) so that the ratio of the NOx increase ratio "Xi" of the integrated value with respect to the smoke increase ratio "Yi" of the integrated value to the target ratio "α0 / β0 "Is controlled: $$"\mathrm{\delta }=\mathrm{<figure-callout\; id="0"\; label="\beta "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\beta </figure-callout>}0\times \text{Xi}-\mathrm{<figure-callout\; id="0"\; label="\alpha "\; filenames="DE102011089847B4\_0008.png"\; state="\{\{state\}\}">\alpha </figure-callout>}0\times \text{Yi}"$$

(M-7) The internal combustion engine to which the present invention is applied should not be limited to the compression ignition type engine. The invention may be applied to a spark ignition type engine, such as e.g. on a gasoline engine of the type with direct injection.

Claims (6)

An engine control device (54) applied to a combustion control system for an internal combustion engine (10) having an external EGR device (48) that is operated such that a portion of an exhaust gas discharged from the engine via an EGR Passage (45, 46) is returned to an inlet air passage (12), with: an oxygen concentration providing section (B1) for providing an oxygen concentration in an intake gas supplied to the engine (10) and an oxygen concentration in the exhaust gas discharged from the engine (10) through an estimation process; a smoke rising ratio calculating section (B3, B4, B7, B8) for estimating a smoke emission amount in the exhaust gas based on the oxygen concentration in the exhaust gas and calculating a smoke rising rate (ΔPM, Yi) from a current value of an estimated smoke emission amount and a smoke amount reference value; a NOx increase ratio calculating section (B2, B4, B5, B6) for estimating a NOx emission amount in the exhaust gas based on the oxygen concentration in the intake gas and calculating a NOx increase rate (ΔNOx, Xi) from a current value of an estimated NOx emission amount and a reference value for an amount of NOx; and an EGR control section (B9, B10, B11, B12) for controlling an EGR amount by operating the external EGR device (48) based on the smoke rising rate (ΔPM, Yi) and the NOx rising rate (ΔNOx, Xi), in which the smoke increase ratio calculating section (B3, B4, B7, B8) has a target value setting section (B4) for calculating and setting a smoke target value as a reference value for the smoke amount from an operating state of the engine (10), and the NOx rising ratio calculating section (B2, B4, B5, B6) has a target value setting section (B4) for calculating and setting a NOx target value as the reference value for the NOx amount based on the operating state of the engine (10), the smoke rising ratio calculating section (B3, B4, B7, B8) has an integrated value calculating section (B8) for calculating a smoke value integrated value as well as an integrated smoke emission amount value, the integrated value calculating section (B8) further including a smoke rising ratio (B8); Yi) of the integrated value of the estimated smoke emission amount with respect to the integrated value of the smoke setpoint, the NOx rising ratio calculating section (B2, B4, B5, B6) has an integrated value calculating section (B6) for calculating an integrated value of the NOx target value as well as an integrated value of the estimated NOx emission amount, the integrated section calculating section (B6) Value further calculates a NOx increase ratio (Xi) of the integrated value of the estimated NOx emission amount with respect to the integrated value of the NOx target value, and the EGR control section (B9, B10, B11, B12) sets the target ratio (α0 / β0) of the NOx increase rate (ΔNOx, Xi) with respect to the smoke increase rate (ΔPM, Yi) depending on the smoke increase ratio (Yi) of the integrated value and changes the NOx increase ratio (Xi) of the integrated value. Machine control device (54) according to Claim 1 wherein the EGR control section (B9, B10, B11, B12) controls the EGR amount so that a ratio of the NOx increase rate (ΔNOx, Xi) with respect to the Smoke increase rate (ΔPM, Yi) is controlled to a desired ratio (α0 / β0). Machine control device (54) according to Claim 1 wherein the smoke rise ratio calculation section (B3, B4, B7, B8) calculates a ratio of the smoke emission amount to the target smoke amount as smoke increase rate (ΔPM, Yi), and the NOx increase ratio calculation section (B2, B4, B5, B6) increases a ratio of the NOx emission amount of the target NOx amount is calculated as NOx increase rate (ΔNOx, Xi). Machine control device (54) according to one of Claims 1 or 3 wherein the target value setting section (B4) sets the smoke target smoke quantity and the NOx target NOx control target each smaller than respective thresholds, and the EGR control section (B9, B10, B11, B12) sets the EGR amount so that any amount of the estimated smoke emission amount and the estimated NOx emission amount becomes smaller than the corresponding limit values. Machine control device (54) according to one of Claims 1 to 4 , further comprising: a turbocharger (16) provided between the intake air passage (12) and the exhaust gas passage (36) for charging the intake air supplied into the engine (10), the external EGR engine comprising at least one of the following valves is constructed; an EGR valve (48) provided in a high-pressure EGR passage (45) to communicate the exhaust passage (36) on an upstream side of an exhaust gas turbine (16b) of the turbocharger (16) with the intake air passage (12) connect; an exhaust throttle valve (52) provided in the exhaust passage (36) on a downstream side of a branch point of a low-pressure EGR passage (46) communicating with the exhaust passage (36) on a downstream side of the exhaust turbine (16b) Inlet air passage (12) connects; and a throttle valve (20) provided in the intake air passage (12) on an upstream side of a connection point for the high-pressure EGR passage (45). Machine control device (45) according to one of Claims 1 to 5 wherein the engine (10) is a compression-ignition type internal combustion engine.

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