JP6404090B2 - EGR valve control device - Google Patents

Description

  The present invention relates to an EGR valve control device that controls the opening of an EGR valve.

  2. Description of the Related Art Conventionally, diesel engines are equipped with an exhaust gas recirculation (EGR) device that introduces a portion of exhaust gas into an intake passage in order to reduce NOx contained in the exhaust gas (for example, a patent) Reference 1). The EGR device includes an EGR valve in an EGR passage connecting the exhaust passage and the intake passage, and adjusts the amount of EGR gas introduced into the intake passage by controlling the opening of the EGR valve.

JP 2002-332879 A

  By the way, when excessive EGR gas is introduced into the intake passage, air is insufficient during combustion of the air-fuel mixture and a large amount of smoke is generated. Such smoke is likely to occur when the engine operating state is in a transient state, that is, when the fuel injection amount continuously increases.

  An object of this invention is to provide the control apparatus of the EGR valve which can suppress generation | occurrence | production of smoke when the operating state of an engine is in a transient state.

  An EGR valve control device that solves the above problem is an EGR valve control device that controls the opening degree of an EGR valve based on a target EGR amount, and is a target of an excess air ratio when it is assumed that the engine is in a steady state. A first excess ratio calculation unit that calculates a first excess ratio that is a value, and a second excess ratio calculation that calculates a second excess ratio that is a target value of the excess air ratio when the engine is assumed to be in a transient state A target excess rate setting unit that sets a target excess rate based on the first excess rate, the second excess rate, and the change amount of the fuel injection amount, and a predicted value of the maximum injection amount at the next fuel injection An injection amount prediction unit that calculates the target excess rate, a target air amount calculation unit that calculates a target air amount by multiplying the target excess rate by the predicted value and a stoichiometric mixture ratio, and a working gas amount sucked by the engine By subtracting the target air amount, A target EGR amount calculation unit that calculates an EGR amount, and the target excess rate setting unit sets the first excess rate to the target excess rate when the amount of change is equal to or less than a first threshold, When the amount of change is greater than the first threshold and less than or equal to the second threshold, the greater the amount of change, the smaller the ratio of the first excess ratio and the ratio of the second excess ratio. A large value is set as the target excess rate, and when the amount of change is larger than the second threshold, the second excess rate is set as the target excess rate.

  According to the above configuration, when the operating state of the engine changes from the steady state to the transient state, and the change amount of the fuel injection amount changes from a value smaller than the first threshold value to a value larger than the second threshold value, The target excess rate gradually changes from the first excess rate to a value close to the second excess rate, and is eventually set to the second excess rate. That is, the target excess rate gradually changes from a target value suitable for the steady state to a target value suitable for the transient state. Thereby, the opening degree of the EGR valve is continuously controlled from the opening degree suitable for the steady state to the opening degree suitable for the transient state, and it becomes difficult to introduce excessive EGR gas into the intake passage. As a result, the generation of smoke in a transient state is suppressed.

  The control device for the EGR valve calculates the steady excess rate with reference to a steady excess rate map that defines a steady excess rate that is a provisional value of the first excess rate according to the engine speed and the fuel injection amount. The transient excess rate is calculated with reference to a transient excess rate map that defines a transient excess rate that is a provisional value of the second excess rate according to the engine speed and the fuel injection amount. The smoke excess excess rate is calculated with reference to a smoke excess excess rate map that defines a smoke excess excess rate that is a smoke excess air excess rate according to the engine speed and the EGR rate. A smoke limit excess rate calculating unit for calculating, wherein the first excess rate calculation unit calculates a larger one of the steady excess rate and the smoke limit excess rate as the first excess rate, and the second excess rate The excess rate calculation unit includes the transient excess rate and the smoke limit. It is preferable to calculate the larger of the Amaritsu as said second excess.

  According to the above configuration, since both the first excess rate and the second excess rate are set to values equal to or higher than the smoke limit excess rate, the target excess rate can be maintained at a value higher than the smoke limit excess rate. As a result, the generation of smoke in the transient state is suppressed with a higher probability.

  In the EGR valve control device, it is preferable that the transient excess rate map is associated with the same fuel injection amount so that the transient excess rate increases as the engine speed increases.

  As the engine speed increases, not only the time during which fuel can be injected is shortened, but also the time during which the air-fuel mixture is generated and the time during which the air-fuel mixture burns are shortened, so that smoke tends to be generated. According to the above configuration, even when the fuel injection amount is the same, the air introduced into the engine can be increased as the engine speed increases.

In the EGR valve control apparatus, it is preferable that the smoke limit excess rate map is associated with the same EGR rate so that the smoke limit excess rate increases as the engine speed increases.
According to the above configuration, even when the EGR rate is the same, the air introduced into the engine can be increased as the engine speed is higher.

  In the EGR valve control apparatus, it is preferable that the steady excess rate map is associated with the steady excess rate that is larger as the fuel injection amount is smaller for the same engine speed.

  According to the above configuration, when the engine is in a steady state, the air introduced into the engine increases as the fuel injection amount decreases even at the same engine speed. As a result, the engine output can be efficiently obtained in a steady state where the fuel injection amount is small.

It is a schematic block diagram which shows schematic structure of the engine system carrying the control apparatus of the EGR valve of one Embodiment. It is a block diagram which shows the function structure of a control apparatus. It is a graph which shows typically an example of a steady excess rate map. It is a graph which shows typically an example of a smoke limit excess rate map. It is a graph which shows typically an example of a transient excess rate map. It is a graph which shows an example of a coefficient table typically. It is a graph which shows typically the relation between engine number of rotations and the maximum injection quantity.

  With reference to FIGS. 1-7, one Embodiment which actualized the control apparatus of the EGR valve is described. First, an overall configuration of an engine system on which an EGR valve control device is mounted will be described with reference to FIG.

  As shown in FIG. 1, the engine system includes a diesel engine 10 (hereinafter referred to as an engine 10). The cylinder block 11 of the engine 10 is formed with four cylinders 12 arranged in a row. Fuel is injected into each cylinder 12 from an injector 13. Connected to the cylinder block 11 are an intake manifold 14 for supplying intake air to each cylinder 12 and an exhaust manifold 15 into which exhaust gas from each cylinder 12 flows.

  In the intake passage 16 connected to the intake manifold 14, an air cleaner (not shown), a compressor 18 constituting a turbocharger 17, and an intercooler 19 are provided in order from the upstream side. The exhaust passage 20 connected to the exhaust manifold 15 is provided with a turbine 22 that is connected to the compressor 18 via a connecting shaft and constitutes the turbocharger 17.

  The engine system includes an EGR passage 25 that connects the exhaust manifold 15 and the intake passage 16. An EGR cooler 26 is provided in the EGR passage 25, and an EGR valve 27 capable of changing the flow path cross-sectional area of the EGR passage 25 is provided on the intake passage 16 side of the EGR cooler 26. When the EGR valve 27 is in an open state, a part of the exhaust gas is introduced into the intake passage 16 through the EGR passage 25 as EGR gas. The cylinder 12 is supplied with a working gas that is a mixed gas of exhaust gas and intake air.

  The engine system includes an intake air amount sensor 30, an intake pressure sensor 31, an intake air temperature sensor 32, an engine speed sensor 34, an EGR pressure sensor 35, an EGR temperature sensor 36, and a coolant temperature sensor 37.

  The intake air amount sensor 30 detects an intake air amount Ga that is the mass weight of the intake air flowing through the intake passage 16 upstream of the compressor 18 in the intake passage 16. The intake pressure sensor 31 detects the working gas pressure Pwg, which is the pressure of the working gas, on the downstream side of the connection portion between the intake passage 16 and the EGR passage 25. The intake air temperature sensor 32 detects a working gas temperature Twg that is the temperature of the working gas in the intake manifold 14. The engine speed sensor 34 detects an engine speed Ne that is the speed of the crankshaft 10a. The EGR pressure sensor 35 and the EGR temperature sensor 36 are located between the EGR cooler 26 and the EGR valve 27 in the EGR passage 25. The EGR pressure sensor 35 detects an EGR pressure Pegr that is the pressure of the EGR gas flowing into the EGR valve 27. The EGR temperature sensor 36 detects an EGR temperature Tegr that is the temperature of the EGR gas flowing into the EGR valve 27. The cooling water temperature sensor 37 detects a cooling water temperature Tw that is the temperature of the cooling water that cools the engine 10. Each of the sensors 30 to 37 outputs a signal indicating the detected detection value to the control device 50 that controls the opening degree of the EGR valve 27.

  Further, a signal indicating the fuel injection amount Gf is input to the control device 50 from the fuel injection control unit 38 that controls fuel injection. The fuel injection control unit 38 outputs a signal indicating the fuel injection amount Gf at the current injection timing to the control device 50 at each injection timing.

  The fuel injection control unit 38 controls the fuel injection amount Gf according to a driver request based on, for example, the engine speed Ne and the accelerator opening ACC. The fuel injection control unit 38 sets a maximum injection amount that is a limit value of the next fuel injection amount Gf based on the engine speed Ne and the current fuel injection amount Gf, and performs fuel injection within a range below the maximum injection amount. The amount Gf is controlled. This is based on the fact that if the fuel injection amount Gf is increased in accordance with the accelerator opening ACC when the accelerator opening ACC suddenly increases, a large amount of smoke is generated due to a shortage of air. Even if the engine 10 is in a transient state, the fuel injection control unit 38 gradually increases the fuel injection amount Gf while keeping the fuel injection amount Gf below the maximum injection amount.

  The control device 50 is mainly configured by a microcomputer having a CPU, a ROM in which various control programs and various data are stored, and a RAM in which various calculation results and various data are temporarily stored. Based on signals from various sensors and the like, the control device 50 controls the intake air amount Ga, the working gas pressure Pwg, the working gas temperature Twg, the engine speed Ne, the EGR pressure Pegr, the EGR temperature Tegr, the cooling water temperature Tw, and the fuel. The injection amount Gf is acquired as information regarding the operating state of the engine 10. The control device 50 calculates the instruction opening VTcom based on the acquired various information and various control programs and various data stored in the ROM, and outputs a signal indicating the instruction opening VTcom to the EGR valve 27. .

  As shown in FIG. 2, the control device 50 includes a working gas amount calculation unit 55 that calculates a working gas amount Gwg that is a mass flow rate of the working gas supplied to the cylinder 12. The working gas amount calculation unit 55 calculates a value obtained by multiplying the state equation P × V = Gwg × R × T by “P” as the working gas pressure Pwg and “V” as the engine rotational speed Ne and the exhaust amount D of the engine 10. The working gas amount Gwg is calculated by substituting the gas constant for “R” and the working gas temperature Twg for “T”.

  The control device 50 includes an EGR rate calculation unit 56 that calculates the EGR rate η of the working gas supplied to the cylinder 12. The EGR rate calculating unit 56 calculates the EGR gas amount Gegr by subtracting the intake air amount Ga detected by the intake air amount sensor 30 from the working gas amount Gwg calculated by the working gas amount calculating unit 55. Then, an EGR rate η (= Gegr / Gwg) that is a ratio of the EGR gas amount Gegr to the working gas amount Gwg is calculated.

  The control device 50 includes a steady excess rate calculating unit 57 that calculates the steady excess rate λa as a provisional value of the first excess rate λ1, which is a target value of the excess air rate when the engine 10 is assumed to be in a steady state. The steady excess rate calculating unit 57 calculates the steady excess rate λa by interpolating values obtained by applying the engine speed Ne and the fuel injection amount Gf to the steady excess rate map 58 based on the coolant temperature Tw.

  As shown in FIG. 3, the steady excess rate map 58 is defined for each of the three cooling water temperatures Tw1, Tw2, Tw3, for example. Each of the steady excess rate maps 58 is data defining a steady excess rate λa corresponding to the engine speed Ne and the fuel injection amount Gf, and is stored in the ROM of the control device 50. The steady excess ratio λa is set based on the results of experiments and simulations performed in advance, and the value tends to increase as the fuel injection amount Gf decreases even at the same engine speed Ne. This is based on the degree of NOx generation. That is, in a steady state where the fuel injection amount Gf is small, NOx is not easily generated due to low combustion temperature and combustion pressure, so that fuel is efficiently burned by introducing more air into the cylinder 12. As a result, the output of the engine 10 can be obtained efficiently, and fuel consumption can be improved. On the other hand, in a steady state where the fuel injection amount Gf is large, the combustion temperature and the combustion pressure are high and NOx is easily generated, so that a lot of EGR gas is introduced into the cylinder 12. Thereby, the production | generation of NOx can be suppressed.

  Further, the steady excess rate λa tends to decrease as the engine speed Ne increases even if the fuel injection amount Gf is the same. This is based on the fact that the higher the engine speed Ne, the shorter the fuel injection time of the injector 13 and the shorter the mixing time of the working gas and fuel and the combustion time of the air-fuel mixture in the cylinder 12. That is, when the engine speed Ne is high, the mixing time of the fuel and air is short before and after the air-fuel mixture ignites, so that a region where the fuel is rich is easily formed in the cylinder 12. Therefore, a larger value is set as the steady excess ratio λa as the engine speed Ne is higher, so that the air introduced into the cylinder 12 is increased as the engine speed Ne is higher. This makes it difficult for a fuel rich region to be formed in the cylinder 12.

  Moreover, the steady excess rate calculating part 57 calculates the value interpolated based on the cooling water temperature Tw as the steady excess rate λa. For example, when the cooling water temperature Tw is Tw1 <Tw <Tw2, the steady excess rate calculating unit 57 calculates the steady excess rate λa1 obtained from the steady excess rate map 58 in which the cooling water temperature Tw is Tw1, and the cooling water. The steady excess ratio λa2 obtained from the steady excess ratio map 58 when the temperature Tw is Tw2 is calculated. Then, the steady excess rate calculating unit 57 calculates the steady excess rate λa by interpolating the steady excess rates λa1 and λa2 based on the cooling water temperatures Tw, Tw1 and Tw2. The steady excess rate λa1 corresponding to the cooling water temperature Tw1 is higher than the steady excess rate λa2 corresponding to the cooling water temperature Tw2. This is because the cylinder block 11 and the piston are quickly raised to an appropriate temperature by increasing the combustion temperature.

  The control device 50 includes a smoke limit excess rate calculating unit 59 that calculates the smoke limit excess rate λmin based on the engine speed Ne detected by the engine speed sensor 34 and the EGR rate η calculated by the EGR rate calculation unit 56. . The smoke limit excess rate calculating unit 59 calculates the smoke limit excess rate λmin by applying the EGR rate η and the engine speed Ne to the smoke limit excess rate map 60. The smoke limit excess rate λmin is a smoke limit that suppresses the generation of smoke when the working gas having an EGR rate η is introduced into the cylinder 12 under the engine speed Ne, or the smoke generation amount falls within an allowable range. It is the excess air ratio shown.

  As shown in FIG. 4, the smoke limit excess rate map 60 is data defining the smoke limit excess rate λmin according to the EGR rate η and the engine speed Ne, and is stored in the ROM of the control device 50. The smoke limit excess rate λmin is set based on the results of experiments and simulations performed in advance, and has a tendency to increase as the engine speed Ne increases even at the same EGR rate η. This is based on the fact that the fuel injection time in the injector 13, the mixing time in the cylinder 12, and the combustion time are shorter as the engine speed Ne is higher, like the steady excess ratio λa.

  The control device 50 includes a transient excess rate calculating unit 61 that calculates the transient excess rate λb as a provisional value of the second excess rate λ2, which is the target value of the excess air rate when the engine 10 is assumed to be in a transient state. The transient excess rate calculation unit 61 calculates the transient excess rate λb by applying the engine speed Ne and the fuel injection amount Gf to the transient excess rate map 62.

  As shown in FIG. 5, the transient excess rate map 62 is data defining the transient excess rate λb according to the engine speed Ne and the fuel injection amount Gf, and is stored in the ROM of the control device 50. The transient excess rate λb is set based on the results of experiments and simulations performed in advance. Even when the fuel injection amount Gf is the same, the transient excess rate λb tends to increase as the engine speed Ne increases. This is based on the fact that the fuel injection time in the injector 13, the mixing time and the combustion time in the cylinder 12 become shorter as the engine speed Ne becomes higher, as with the steady excess ratio λa.

  Further, the transient excess rate λb tends to increase as the fuel injection amount Gf increases even at the same engine speed Ne. Thereby, the air introduced into the cylinder 12 increases as the fuel injection amount Gf increases even at the same engine speed Ne.

  The control device 50 includes a first excess ratio calculation unit 63 that calculates a first excess ratio λ1 that is a target value of the excess air ratio when it is assumed that the operating state of the engine 10 is a steady state. The first excess rate calculating unit 63 calculates a higher one of the steady excess rate λa calculated by the steady excess rate calculating unit 57 and the smoke limit excess rate λmin calculated by the smoke limit excess rate calculating unit 59 as the first excess rate λ1. Calculate as

  The control device 50 includes a second excess ratio calculation unit 64 that calculates a second excess ratio λ2 that is a target value of the excess air ratio when the operating state of the engine 10 is assumed to be a transient state. The second excess rate calculating unit 64 calculates the higher of the transient excess rate λb calculated by the transient excess rate calculating unit 61 and the smoke limit excess rate λmin calculated by the smoke limit excess rate calculating unit 59 as the second excess rate λ2. Calculate as

  The control device 50 includes a coefficient calculation unit 65 that calculates a coefficient k used when calculating the target excess ratio tλ that is the final target value of the excess air ratio. The coefficient k is set to a value indicating the ratio of the first excess ratio λ1 and the ratio of the second excess ratio λ2 in the target excess ratio tλ. The coefficient calculation unit 65 calculates a change amount ΔGf of the fuel injection amount Gf by subtracting the previous fuel injection amount Gf from the current fuel injection amount Gf, and applies the change amount ΔGf to the coefficient table 66 to obtain a coefficient. k is calculated. When the fuel injection amount Gf increases, the change amount ΔGf takes a positive value.

  As shown in FIG. 6, the coefficient table 66 is data that uniquely defines the coefficient k with respect to the change amount ΔGf, and is stored in the ROM of the control device 50. The coefficient k is set based on the results of experiments and simulations performed in advance. In the coefficient table 66, the coefficient k = 0 is associated with the change amount ΔGf that is equal to or less than the first threshold value ΔGf1 (> 0). In the coefficient table 66, a coefficient that is larger than the first threshold value ΔGf1 and less than or equal to the second threshold value ΔGf2 (> ΔGf1) is closer to 1 as the variation amount ΔGf is larger. k is associated. In the coefficient table 66, a coefficient k = 1 is defined for the change amount ΔGf that is larger than the second threshold value ΔGf2.

The control device 50 includes a target excess rate setting unit 67 that sets the target excess rate tλ. The target excess rate setting unit 67 sets a calculated value obtained by substituting the first excess rate λ1, the second excess rate λ2, and the coefficient k into the following relational expression (1) as the target excess rate tλ.
tλ = (1−k) × λ1 + k × λ2 (1)

  The control device 50 includes an injection amount prediction unit 68 that calculates a predicted value Gfmax of the maximum injection amount at the next injection timing. The injection amount prediction unit 68 calculates a predicted value Gfmax based on the engine speed Ne and the fuel injection amount Gf.

  As shown in FIG. 7, the injection amount prediction unit 68 treats the engine speed Ne as a parameter that defines an angle θ indicating a unit increase amount of fuel with respect to the current fuel injection amount Gf. This is because the higher the engine speed Ne, the greater the amount of air that can be sucked into the cylinder 12, and the maximum injection amount at the next injection timing differs depending on the engine speed Ne even if the fuel injection amount Gf is the same. based on. The injection amount prediction unit 68 calculates the predicted value Gfmax by increasing the current fuel injection amount Gf by a unit increase amount based on the engine speed Ne.

The control device 50 includes a target air amount calculation unit 69 that calculates a target air amount tGa at the next injection timing. The target air amount calculation unit 69 has the following relational expression (2) showing the target excess rate tλ set by the target excess rate setting unit 67, the predicted value Gfmax calculated by the injection amount prediction unit 68, and the stoichiometric mixture ratio λth. Is substituted into the target air amount tGa.
tGa = tλ × Gfmax × λth (2)

  The control device 50 includes a target EGR amount calculation unit 70 that calculates a target EGR amount tGegr that is a target value of the EGR gas amount at the next injection timing. The target EGR amount calculation unit 70 calculates the target EGR amount tGegr by subtracting the target air amount tGa calculated by the target air amount calculation unit 69 from the working gas amount Gwg calculated by the working gas amount calculation unit 55.

  The control device 50 includes a basic opening degree calculation unit 71 that calculates the basic opening degree VTst of the EGR valve 27. The basic opening degree calculation unit 71 detects the target EGR amount tGegr calculated by the target EGR amount calculation unit 70, the EGR pressure Pegr detected by the EGR pressure sensor 35, the EGR temperature Tegr detected by the EGR temperature sensor 36, and the intake pressure sensor 31 The basic opening area A of the EGR valve 27 is calculated by substituting the working gas pressure Pwg into the following relational expression (3). In the relational expression (3), “R” is a gas constant, and “κ” is a specific heat ratio of the exhaust gas. The basic opening calculation unit 71 calculates, for example, an opening obtained by applying the basic opening area A to an opening table in which the opening with respect to the opening area is uniquely defined as the basic opening VTst.

  The control device 50 includes an F / B opening degree calculation unit 72 that calculates an F / B opening degree VTfb added to the basic opening degree VTst in order to feedback control the opening degree of the EGR valve 27. The F / B opening degree calculation unit 72 calculates a deviation ΔGa between the target air amount tGa calculated by the target air amount calculation unit 69 and the intake air amount Ga that is a detection value of the intake air amount sensor 30. The F / B opening degree calculation unit 72 calculates the F / B opening degree VTfb by adding a value obtained by multiplying the deviation ΔGa by a proportional gain and a value obtained by multiplying the integrated value of the deviation ΔGa by an integral gain.

  The control device 50 includes an instruction opening calculator 73 that calculates an instruction opening VTcom to be output to the EGR valve 27. The command opening calculation unit 73 adds the F / B opening VTfb calculated by the F / B opening calculation unit 72 to the basic opening VTst calculated by the basic opening calculation unit 71, thereby giving the command opening VTcom. Is calculated.

  Next, an example of the operation of the control device 50 described above will be described taking as an example a case where the operating state of the engine 10 has changed from a steady state to a sudden acceleration state. At this time, the change amount ΔGf changes from a value equal to or smaller than the first threshold value ΔGf1 to a value larger than the second threshold value ΔGf2.

  Based on various information acquired by the control device 50, the working gas amount calculation unit 55 calculates the working gas amount Gwg, and the EGR rate calculation unit 56 calculates the EGR rate η. Further, the steady excess rate calculating unit 57 calculates the steady excess rate λa as a provisional value of the first excess rate λ1, which is the target value of the excess air rate in the steady state. The smoke limit excess rate calculator 59 calculates the smoke limit excess rate λmin, which is the smoke excess air excess rate. The transient excess ratio calculation unit 61 calculates the transient excess ratio λb as a provisional value of the second excess ratio λ2, which is the target value of the excess air ratio in the transient state. Then, the first excess rate calculating unit 63 calculates the higher one of the steady excess rate λa and the smoke limit excess rate λmin as the first excess rate λ1. In addition, the second excess ratio calculation unit 64 calculates the higher one of the transient excess ratio λb and the smoke limit excess ratio λmin as the second excess ratio λ2.

  When the engine 10 is in a steady state, the coefficient calculation unit 65 calculates the coefficient k = 0, and the target excess rate setting unit 67 sets the first excess rate λ1 to the target excess rate tλ. When the operating state of the engine 10 shifts from the steady state to the rapid acceleration state, the coefficient calculation unit 65 calculates a coefficient k greater than 0 because the change amount ΔGf exceeds the first threshold value ΔGf1. Thereby, the target excess ratio setting unit 67 sets the calculated value in which the ratio of the first excess ratio λ1 is small and the ratio of the second excess ratio λ2 is increased to the target excess ratio tλ. Then, as the amount of change ΔGf increases, the coefficient calculation unit 65 calculates a coefficient k close to 1, and the target excess rate setting unit 67 sets the calculated value obtained by further increasing the ratio of the second excess rate λ2 as the target excess rate. Set to tλ. When the change amount ΔGf eventually exceeds the second threshold value ΔGf2, the coefficient calculation unit 65 calculates the coefficient k = 1, and the target excess rate setting unit 67 sets the second excess rate λ2 to the target excess rate tλ.

  The target air amount calculation unit 69 calculates the target air amount tGa based on the target excess rate tλ and the predicted value Gfmax of the maximum injection amount. This target air amount tGa is an air amount that can suppress the generation of smoke even when the maximum injection amount of fuel is injected at the next injection timing. The target EGR amount calculation unit 70 calculates the target EGR amount tGegr by subtracting the target air amount tGa from the working gas amount Gwg. Then, the command opening calculation unit 73 is based on the EGR valve 27 based on the basic opening VTst based on the target EGR amount tGegr and the F / B opening VTfb based on the deviation ΔGa between the target air amount tGa and the intake air amount Ga. The command opening VTcom is calculated.

  That is, when the operating state of the engine 10 shifts from the steady state to the transient state, the target excess rate tλ gradually changes from the excess air rate suitable for the steady state to the excess air rate suitable for the transient state. . Thereby, the opening degree of the EGR valve 27 is continuously controlled from the opening degree suitable for the steady state to the opening degree suitable for the transient state.

According to the control apparatus 50 of the said embodiment, the effect enumerated below is acquired.
(1) When the operating state of the engine 10 changes from the steady state to the transient state, the opening degree of the EGR valve 27 is continuously controlled from the opening degree suitable for the steady state to the opening degree suitable for the transient state. Therefore, it becomes difficult to introduce excessive EGR gas into the intake passage 16, and the generation of smoke in a transient state is suppressed.

  In particular, in the engine 10 provided with the turbocharger 17, when the operating state changes from a low-speed steady state to a transient state, there may be a time difference between the increase in the engine speed Ne and the increase in the supercharging pressure. In such a case, if the opening degree of the EGR valve 27 is controlled to an opening degree corresponding to the transient state while the supercharging by the turbocharger 17 is insufficient, excessive EGR gas is introduced into the intake passage 16. End up. In this regard, the control device 50 gradually controls the opening degree of the EGR valve 27 to an opening degree suitable for the transient state, so that even in the engine 10 equipped with the turbocharger 17, smoke is generated in the transient state. Is suppressed.

  (2) The target air amount tGa is calculated based on the predicted value Gfmax of the maximum injection amount at the next injection timing, and the difference between the working gas amount Gwg and the target air amount tGa is calculated as the target EGR amount tGegr. Therefore, even if the maximum injection amount of fuel is injected at the next injection timing, air shortage during combustion is suppressed.

  (3) The first excess ratio calculation unit 63 calculates the higher of the steady excess ratio λa and the smoke limit excess ratio λmin as the first excess ratio λ1. Similarly, the second excess rate calculating unit 64 calculates the higher of the transient excess rate λb and the smoke limit excess rate λmin as the second excess rate λ2. Therefore, both the first excess rate λ1 and the second excess rate λ2 are set to values equal to or greater than the smoke limit excess rate λmin. As a result, the target excess rate tλ can be maintained at a value equal to or higher than the smoke limit excess rate λmin.

  (4) The steady excess ratio λa tends to increase as the fuel injection amount Gf decreases even at the same engine speed Ne. As a result, the air introduced into the cylinder 12 increases as the fuel injection amount Gf decreases even at the same engine speed Ne. As a result, fuel can be burned efficiently, and the engine 10 can be operated efficiently.

  (5) The steady excess ratio λa tends to decrease as the engine speed Ne increases with respect to the same fuel injection amount Gf. Thereby, the air introduced into the cylinder 12 increases as the mixing time of the mixture and the combustion time of the mixture become shorter. As a result, a fuel rich region is hardly formed in the cylinder 12.

  (6) The transient excess rate λb tends to increase as the engine speed Ne increases with respect to the same fuel injection amount Gf. As a result, as in (5) above, it is difficult to form a fuel rich region in the cylinder 12.

  (7) The smoke limit excess rate λmin tends to increase as the engine speed Ne increases with respect to the same EGR rate η. As a result, similarly to the above (5), it is difficult to form a fuel rich region in the cylinder 12.

  (8) When the change amount ΔGf is larger than the first threshold value ΔGf1, it is preferable that the operating state of the engine 10 is a rapid acceleration state in which the increase amount of the accelerator opening ACC per unit time is larger than a predetermined value. According to such a configuration, the frequency at which the coefficient k is switched between the state where the coefficient k = 0 and the state where the coefficient k> 0 is suppressed. As a result, the change in the amount of air that can cause the driver to feel uncomfortable is suppressed.

  (9) The control device 50 calculates an opening obtained by adding the F / B opening VTfb to the basic opening VTst as the instruction opening VTcom. As a result, the EGR valve 27 is controlled to an opening that takes into account the deviation ΔGa between the current intake air amount Ga and the target air amount tGa, and the target EGR amount tGegr and the EGR amount actually introduced into the intake passage 16 are The difference can be reduced.

In addition, the said embodiment can also be suitably changed and implemented as follows.
The control device 50 calculates the target air amount tGa based on the predicted value Gfmax. On the other hand, in the steady state, the fuel injection amount Gf that the fuel injection control unit 38 instructs to the injector 13 at the next injection timing is a value smaller than the predicted value Gfmax. Therefore, the transient excess rate λb is preferably set to a value equal to or less than the steady excess rate λa associated with the same engine speed Ne and the same fuel injection amount Gf. According to such a configuration, in the steady state, more air is introduced into the cylinder 12 than in the transient state, so that the engine 10 can be operated efficiently while suppressing the generation of smoke.

  In the control device 50, the F / B opening degree calculation unit 72 is not limited to the F / B opening degree VTfb based on the deviation ΔGa between the target air amount tGa and the intake air amount Ga, for example, the target EGR amount tGegr and the current EGR The F / B opening degree VTfb may be calculated based on the deviation from the amount. The current EGR amount may be, for example, a value detected by a sensor that detects the flow rate of EGR gas in the EGR passage 25. Further, for example, a sensor for detecting the flow rate of the exhaust gas may be provided in the exhaust passage 20, and a value obtained by subtracting the detection value of the sensor from the working gas amount Gwg may be used.

-In the control apparatus 50, the F / B opening calculating part 72 may be omitted. That is, the control device 50 may control the opening degree of the EGR valve 27 using the basic opening degree VTst as the instruction opening degree.
The first threshold value ΔGf1 may be a value that the change amount ΔGf exceeds when the change amount ΔGf of the fuel injection amount Gf is a gradual acceleration state than when the operating state of the engine 10 is a rapid acceleration state.

  The steady excess ratio λa is not limited to a value that tends to increase as the fuel injection amount Gf decreases even at the same engine speed Ne. The steady excess ratio λa may be a value that can be a target value of the excess air ratio in the steady state. For example, at a specific engine speed Ne, the steady excess ratio λa may be a constant value regardless of the fuel injection amount Gf. The method of obtaining the steady excess rate λa is not limited to the method using the steady excess rate map 58, and is a method of selectively substituting various information input to the control device 50 into a predetermined relational expression. Also good.

  The smoke limit excess rate λmin is not limited to the one having the tendency to increase as the engine speed Ne increases even at the same EGR rate. The smoke limit excess rate λmin only needs to be an air excess rate that satisfies the smoke limit. For example, the smoke limit excess rate λmin may be a constant value for each EGR rate regardless of the engine speed Ne. Further, the method of obtaining the smoke limit excess rate λmin is not limited to the method using the smoke limit excess rate map 60, but is a method of selectively substituting various information input to the control device 50 into a predetermined relational expression. There may be.

  The transient excess rate λb is not limited to the one having the tendency to increase as the engine speed Ne increases even with the same fuel injection amount. The transient excess rate λb only needs to be a value that can be the target value of the excess air ratio in the transient state. For example, at a specific engine speed Ne, the transient excess rate λb may be a constant value regardless of the fuel injection amount Gf. The method of obtaining the transient excess rate λb is not limited to the method using the transient excess rate map 62, and is a method of selectively substituting various information input to the control device 50 into a predetermined relational expression. Also good.

  The control device 50 may not include the smoke limit excess rate calculation unit 59. In this case, the steady excess rate calculation unit 57 is set as the first excess rate calculation unit, and the transient excess rate calculation unit 61 is set as the second excess rate calculation unit.

  The control device 50 may not include the transient excess rate calculation unit 61. In this case, the steady excess rate calculation unit 57 is set as the first excess rate calculation unit, and the smoke limit excess rate calculation unit 59 is set as the second excess rate calculation unit.

  The injection amount prediction unit 68 calculates a final target fuel injection amount based on the accelerator opening ACC and the engine speed Ne, and based on a deviation between the target fuel injection amount and the current fuel injection amount Gf. The predicted value Gfmax of the maximum injection amount may be calculated.

  The steady excess rate calculation unit 57 may calculate, for example, the value interpolated based on the outside air temperature Tatm as the steady excess rate λa, or the value interpolated based on the cooling water temperature Tw and the outside air temperature Tatm The excess ratio λa may be calculated.

  DESCRIPTION OF SYMBOLS 10 ... Diesel engine, 10a ... Crankshaft, 11 ... Cylinder block, 12 ... Cylinder, 13 ... Injector, 14 ... Intake manifold, 15 ... Exhaust manifold, 16 ... Intake passage, 17 ... Turbocharger, 18 ... Compressor, 19 ... Intercooler , 20 ... exhaust passage, 22 ... turbine, 25 ... EGR passage, 26 ... EGR cooler, 27 ... EGR valve, 30 ... intake air amount sensor, 31 ... intake pressure sensor, 32 ... intake air temperature sensor, 34 ... engine speed sensor 35 ... EGR pressure sensor, 36 ... EGR temperature sensor, 37 ... cooling water temperature sensor, 38 ... fuel injection control unit, 50 ... control device, 55 ... working gas amount calculation unit, 56 ... EGR rate calculation unit, 57 ... steady excess Rate calculation unit, 58 ... Steady excess rate map 59 ... Smoke limit excess rate calculation unit, 60 ... Smoke limit excess rate map, 61 ... Transient excess rate calculation unit, 62 ... Transient excess rate map, 63 ... First excess rate calculation unit, 64 ... Second excess rate calculation unit, 65 ... Coefficient calculation unit, 66 ... Coefficient table, 67 ... Target excess rate setting unit, 68 ... Injection amount prediction unit, 69 ... Target air amount calculation unit, 70 ... Target EGR amount calculation unit, 71 ... Basic opening calculation unit, 72 ... F / B opening degree calculation part, 73 ... Instruction opening degree calculation part.

Claims (5)

A control device for an EGR valve that controls the opening of the EGR valve based on a target EGR amount,
A first excess ratio calculating unit that calculates a first excess ratio that is a target value of the excess air ratio when it is assumed that the engine is in a steady state;
A second excess ratio calculation unit that calculates a second excess ratio that is a target value of the excess air ratio when the engine is assumed to be in a transient state;
A coefficient calculation unit that calculates a coefficient for calculating a target excess rate, which is a target value of the excess air rate used for controlling the EGR valve, based on the amount of change in the fuel injection amount;
Calculated values obtained by substituting the first excess rate, the second excess rate, and the coefficient into an arithmetic expression that includes the first excess rate, the second excess rate, and the coefficient as variables. A target excess rate setting unit for setting the target excess rate,
An injection amount prediction unit for calculating a predicted value of the maximum injection amount at the time of the next fuel injection,
A target air amount calculation unit that calculates a target air amount by multiplying the target excess rate by the predicted value and a stoichiometric mixture ratio;
A target EGR amount calculation unit that calculates the target EGR amount by subtracting the target air amount from the working gas amount sucked by the engine;
The coefficient calculator is
When the amount of change is equal to or less than a first threshold value, the first excess rate is calculated as a value that is set as the target excess rate, and
When the amount of change is greater than the first threshold and less than or equal to the second threshold, the larger the amount of change, the smaller the ratio of the first excess rate and the second excess rate. A value that sets an excess rate with a large ratio as the target excess rate is calculated as the coefficient,
When the change amount is larger than the second threshold value, the EGR valve control device calculates a value at which the second excess rate is set as the target excess rate as the coefficient . A steady excess rate calculating unit that calculates the steady excess rate with reference to a steady excess rate map that defines a steady excess rate that is a provisional value of the first excess rate according to the engine speed and the fuel injection amount;
A transient excess rate calculating unit that calculates the transient excess rate with reference to a transient excess rate map that defines a transient excess rate that is a provisional value of the second excess rate according to the engine speed and the fuel injection amount; ,
A smoke limit excess rate calculating unit that calculates the smoke limit excess rate with reference to a smoke limit excess rate map that defines a smoke limit excess rate that is an excess air rate of the smoke limit according to the engine speed and the EGR rate; With
The first excess rate calculating unit calculates the larger of the steady excess rate and the smoke limit excess rate as the first excess rate,
2. The EGR valve control device according to claim 1, wherein the second excess ratio calculation unit calculates a larger one of the transient excess ratio and the smoke limit excess ratio as the second excess ratio. The control device for an EGR valve according to claim 2, wherein the transient excess ratio map is associated with the same fuel injection amount, the transient excess ratio being larger as the engine speed is higher. The control device for an EGR valve according to claim 2 or 3, wherein the smoke limit excess rate map is associated with the same EGR rate so that the smoke limit excess rate increases as the engine speed increases. The EGR valve according to any one of claims 2 to 4, wherein the steady excess rate map is associated with the same engine speed, the larger the steady excess rate as the fuel injection amount is smaller. Control device.

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