JP6515903B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for controlling an internal combustion engine provided with a turbocharger having a variable nozzle in a turbine and an EGR device.

  Patent Document 1 describes a method of calculating the opening area of a variable nozzle necessary to achieve a target pressure in an exhaust manifold. According to the method disclosed in Patent Document 1, the pressure Pwg downstream of the EGR valve, the pressure Peg upstream of the EGR valve, and the temperature Teg upstream of the EGR valve are respectively acquired by the sensors. The pressure ratio between the pressure Peg on the downstream side of the EGR valve and the pressure Peg on the upstream side of the EGR valve, the temperature Teg on the upstream side of the EGR valve, and the opening degree of the EGR valve An EGR flow amount Geg, which is the flow rate of the EGR gas passing through the EGR valve, is calculated based on the opening area calculated from VTegr.

  According to the method disclosed in Patent Document 1, the working gas amount Gwg, which is the flow rate of the working gas supplied to the cylinder, is then calculated based on the intake temperature Tin and the intake pressure Pwg acquired by the sensor. The flow rate Gti of the exhaust gas flowing into the turbine is calculated by subtracting the EGR flow amount Geg from the working gas amount Gwg. Also, the outlet pressure Pte of the turbine and the inlet temperature Tti of the turbine are calculated based on the associated state quantities. Then, the required opening area Ane of the variable nozzle is calculated based on the target pressure Pme in the exhaust manifold, the outlet pressure Pte, and the inlet temperature Tti of the turbine using a formula based on Bernoulli's theorem.

JP, 2014-047717, A JP, 2015-140718, A Japanese Patent Application Publication No. 08-042380

  Using the equation based on Bernoulli's theorem disclosed in Patent Document 1, it is also possible to calculate the pressure in the exhaust manifold, that is, the estimated value of the turbine upstream pressure from the opening degree of the variable nozzle. Although this calculation requires the flow rate through the turbine, which is the flow rate of exhaust gas passing through the turbine, in the method disclosed in Patent Document 1, this is calculated from the amount of working gas in the cylinder and the amount of EGR flow. It is done. According to the method disclosed in Patent Document 1, the EGR flow rate is calculated based on the pressure ratio before and after the EGR valve. In this case, a sensor for measuring the pressure on the downstream side of the EGR valve and a sensor for measuring the pressure on the upstream side of the EGR valve are respectively required. However, from the viewpoint of reducing the number of parts, the number of sensors should be as small as possible.

  The pressure upstream of the EGR valve can also be calculated from the turbine upstream pressure, if the turbine upstream pressure can be calculated as described above. Therefore, there is a possibility that the sensor for measuring the pressure on the upstream side of the EGR valve can be dispensed with. However, in that case, it is not possible to calculate the EGR flow rate based on the pressure ratio before and after the EGR valve, so if the turbine passing flow rate is not calculated by a method different from the method disclosed in Patent Document 1 It does not.

  One conceivable method is to calculate the flow rate through the turbine from the amount of fresh air measured by the air flow sensor. The flow rate through the turbine has a response delay with respect to the fresh air amount by the time until the gas having passed through the air flow sensor reaches the turbine. The flow rate through the turbine can be calculated by performing delay processing taking into consideration the response delay to the fresh air amount. However, it is difficult to calculate the pressure upstream of the turbine accurately with the flow rate through the turbine calculated from the fresh air amount measured by the air flow sensor because noise tends to get on the measurement value of the air flow sensor.

  The present invention has been made to solve the problems as described above, and provides a control device of an internal combustion engine capable of accurately calculating the pressure upstream of the turbine which is the pressure in the exhaust passage on the inlet side of the turbine. With the goal.

  A control device for an internal combustion engine according to the present invention includes an internal combustion engine including a turbocharger having a variable nozzle in a turbine, and an EGR device having an EGR valve in an EGR passage connecting the upstream of the turbine in the exhaust passage and the intake passage. Is a control device for controlling the In order to achieve the above object, the control device is configured to perform the following processing.

The control device acquires the following state quantities directly or indirectly by the sensor.
The present value P ds of the turbine downstream pressure, which is the pressure in the exhaust passage on the outlet side of the turbine;
The present value Pim of the intake passage pressure which is the pressure in the space to which the EGR passage of the intake passage is connected;
The current value Tus of the upstream temperature of the turbine, which is the temperature in the exhaust passage on the inlet side of the turbine;
Current value θegr of opening degree of EGR valve;
The present value θvn of the closing degree of the variable nozzle and the present value Gadly of the fresh air volume which is the flow rate of fresh air taken into the intake passage.

Further, the control device obtains the following state quantities by calculation.
Current value Gcyl of in-cylinder gas amount calculated from pressure and temperature of gas entering cylinder;
Current value Gf of fuel flow rate of fuel injection valve;
The present value Mtb of the flow rate through the turbine, which is the flow rate of gas passing through the turbine calculated from the present value Gadly of the fresh air amount and the present value Gf of the fuel flow; The present value Megr of the EGR valve passing flow rate calculated from the difference between the sum of the value Gf and the present value Mtb of the turbine passing flow rate

  The control device temporarily stores the previous value Pus_0 of the turbine upstream pressure, which is the pressure in the exhaust passage on the inlet side of the turbine.

  The control device stores in advance a turbine effective opening area map which relates the turbine effective opening area when the turbine including the variable nozzle is regarded as one nozzle to the turbine passing flow rate and the closing degree of the variable nozzle. Further, the control device stores in advance an EGR valve effective opening area map that associates the EGR valve effective opening area when the EGR valve is regarded as one nozzle with the EGR valve passing flow rate and the opening degree of the EGR valve.

  The controller reads out the turbine effective opening area μAtb corresponding to the current value Mtb of the turbine passing flow and the current value θvn of the closing degree of the variable nozzle from the turbine effective opening area map, and the current value Megr of the EGR valve passing flow The EGR valve effective opening area μAegr corresponding to the current value θegr of the opening degree of the EGR valve is read out from the EGR valve effective opening area map.

The present control device divides the function Φ of the pressure ratio π between the downstream pressure and the upstream pressure of the nozzle defined by the following equation 1 into a plurality of pressure ratios π by the piecewise linear method, A first coefficient map that relates each coefficient a, b of the linear function determined for each pressure ratio π division to a pressure ratio π division when linear approximation is performed by the linear function defined by the following equation 2 for each division Is stored in advance.

The control device divides the function Φ of the pressure ratio π between the downstream pressure and the upstream pressure of the nozzle defined by the above equation 1 into a plurality of pressure ratio π divisions by the piecewise linear method, and divides the pressure ratio π The second coefficient map relating each coefficient c, d of the linear function determined for each section of the pressure ratio π to the section of the pressure ratio π when linearly approximated by the linear function defined by the following equation 3 for each It is stored in advance.

  When the ratio of the current value Pds of the turbine downstream pressure to the previous value Pus_0 of the turbine upstream pressure is set as the pressure ratio π in the above equation 2, the present control device has coefficients a and b corresponding to the section to which the pressure ratio π applies. Is read from the first coefficient map, and the pressure ratio π corresponds to the section to which the pressure ratio π applies, where the ratio of the current value Pim of the intake passage pressure to the previous value Pus_0 of the turbine upstream pressure is the pressure ratio The respective coefficients c and d are read out from the second coefficient map.

The present control apparatus sums the present value Pds of the downstream pressure of the turbine, the present value Pim of the intake passage pressure, the present value Tus of the upstream temperature of the turbine, the present value Gcyl of the in-cylinder gas amount and the present value Gf of the fuel flow rate. Based on the turbine effective opening area μAtb, the EGR valve effective opening area μAegr, and the coefficients a, b, c, d, the current value Pus of the turbine upstream pressure is calculated using Equation 4 below.

  The control device controls the internal combustion engine based on the current value Pus of the turbine upstream pressure calculated by the above logic.

  According to this control device, the turbine upstream pressure can be calculated with high accuracy by using the above-mentioned equation 4, and the internal combustion engine can be controlled based on the turbine upstream pressure with high accuracy. In addition, since the flow rate through the turbine used to calculate the turbine effective opening area is calculated based on the fresh air amount, the influence of the variation in the measured value of the fresh air amount due to the noise also extends to the calculated value of the turbine effective opening area . Similarly, since the EGR valve passing flow rate used for calculating the effective opening area of the EGR valve is also calculated using the fresh air amount, the influence of the variation of the measured value of the fresh air amount due to the noise is the calculation of the EGR valve effective opening area It extends to the value. However, the sensitivity of the turbine effective opening area to the variation of the turbine passing flow rate is not high, as judged from the relationship between the turbine effective opening area and the turbine passing flow rate. Similarly, to judge from the relationship between the EGR valve effective opening area and the EGR valve passing flow rate, the sensitivity of the EGR valve effective opening area to the variation of the EGR valve passing flow rate is not high either. Therefore, the influence of the variation in the measured value of the fresh air amount due to noise on the calculation results of the turbine effective opening area and the EGR valve effective opening area is limited, and the turbine effective opening area and the EGR valve effective opening area are used as parameters. The calculation accuracy of the turbine upstream pressure including is fully secured.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the internal combustion engine to which the control apparatus of embodiment of this invention is applied. It is a figure which shows the relationship between the closeness degree of a variable nozzle, the turbine passing flow rate, and the turbine effective opening area. It is a figure which shows the relationship between the opening degree of EGR valve, EGR valve passage flow volume, and EGR valve effective opening area. It is a figure which shows the function phi of pressure ratio pi between the downstream pressure and upstream pressure of the nozzle included in the formula of Bernoulli's theorem, and the linear function which approximated it. FIG. 6 is a view showing a distribution of verification data for verifying the estimation accuracy of the turbine upstream pressure according to Equation 4. FIG. 6 is a diagram showing the degree of agreement between the estimated value of the turbine upstream pressure according to Equation 4 and the actual value of the turbine upstream pressure. It is a block diagram which shows the structure for calculating the turbine upstream pressure which the control apparatus of embodiment of this invention has. It is a figure which shows an example of the application of the estimated value of a turbine upstream pressure. It is a figure which shows an example of the application of the estimated value of a turbine upstream pressure.

1. Configuration of Internal Combustion Engine FIG. 1 is a view showing a schematic configuration of an internal combustion engine 2 to which a control device according to an embodiment of the present invention is applied. The internal combustion engine 2 according to the present embodiment is a single turbo system provided with a single turbocharger 20. The internal combustion engine 2 comprises an engine body 4 configured as a diesel engine. The engine body 4 is provided with a plurality of (four in the drawing) cylinders 4a, and a fuel injection valve 6 is provided for each cylinder 4a.

  An intake passage 8 for taking in fresh air from the outside is connected to the intake port of the engine body 4. In the intake passage 8, an air cleaner 12, a compressor 20a of the turbocharger 20, an intercooler 14 and an intake throttle valve 16 are provided in this order from the upstream side toward the downstream side. At a portion of the intake passage 8 connected to the engine body 4, an intake manifold 8 a for distributing air to the cylinders 4 a is formed. An exhaust passage 10 for exhausting the exhaust gas to the outside is connected to an exhaust outlet of the engine body 4. The exhaust passage 10 is provided with a turbine 20 b of a turbocharger 20. The turbine 20 b includes a variable nozzle 22. At a portion of the exhaust passage 10 connected to the engine body 4, an exhaust manifold 10 a for collecting the exhaust discharged from the cylinders 4 a is formed.

  The internal combustion engine 2 includes an EGR device 30 that recirculates part of the exhaust gas from the exhaust passage 10 to the intake passage 8. The EGR device 30 includes an EGR passage 32 connecting the upstream of the turbine 20 b in the exhaust passage 10 and the downstream of the intake throttle valve 16 in the intake passage 8. An EGR cooler 34 and an EGR valve 36 are disposed in this order in the EGR passage 32 from the upstream side to the downstream side in the direction of flow of the EGR gas. The EGR passage 32 is provided with a bypass passage 38 that bypasses the EGR cooler 34. At a junction where the bypass passage 38 joins the EGR passage 32, a bypass valve 40 is provided which switches the flow path of the EGR gas between the bypass passage 38 and the EGR cooler 34.

  The control device 100 that controls the internal combustion engine 2 is an ECU (Electronic Control Unit) having at least one CPU, at least one ROM, and at least one RAM. The ROM stores various data including various programs and maps for controlling the internal combustion engine 2. Various functions are realized in the control device 100 by loading a program stored in the ROM into the RAM and executing the program by the CPU. Control device 100 may be configured of a plurality of ECUs.

  Various information regarding the operating state and operating conditions of the internal combustion engine 2 are input to the control device 100 from various sensors attached to the internal combustion engine 2. For example, from the air flow sensor 50 disposed in the vicinity of the air cleaner 12, information on the amount of fresh air (Gadly) which is the flow rate of fresh air drawn into the intake passage 8 is input. Information on an intake manifold pressure (Pim) which is a pressure in the intake manifold 8a is input from a pressure sensor 52 disposed in the intake manifold 8a. The intake manifold pressure (Pim) is also an intake passage pressure which is a pressure in a space to which the EGR passage 32 of the intake passage 8 is connected. Information on an intake manifold temperature (Tim) which is a temperature in the intake manifold 8a is input from a temperature sensor 54 disposed in the intake manifold 8a. Further, from the temperature sensor 56 disposed in the exhaust manifold 10a, information on the turbine upstream temperature (Tus) which is the temperature in the exhaust passage on the inlet side of the turbine 20b is input. Information on a turbine downstream pressure (Pds), which is the pressure in the exhaust passage on the outlet side of the turbine 20b, is input from the pressure sensor 58 disposed downstream of the turbine 20b in the exhaust passage 10. Further, information on the opening degree (θ egr) of the EGR valve 36 is inputted from the opening degree sensor provided in the EGR valve 36, and the closing degree of the variable nozzle 22 is received from the closing degree sensor provided in the variable nozzle 22. Information about θ v n) is input. Control device 100 determines control parameters of internal combustion engine 2 based on these pieces of information.

2. Estimation of Turbine Upstream Pressure One of the functions of the control device 100 is a function of estimating the turbine upstream pressure (Pus) which is the pressure in the exhaust passage on the inlet side of the turbine 20b. Calculation of the turbine upstream pressure is performed using Equation 4 above. Hereinafter, how to derive Equation 4 will be described.

2-1. Turbine flow characteristic equation When fluid passes through a nozzle to which the energy conservation law is applied, the relationship between the state quantity of fluid before passing through the nozzle and the state quantity of fluid after passing through the nozzle follows Bernoulli's theorem . Here, if the turbine 20b is a nozzle, the following equation 5 holds. In Equation 5, Mtb is the flow rate through the turbine, which is the flow rate of gas passing through the turbine 20b, and μAtb is the effective opening area of the turbine 20b when the turbine 20b including the variable nozzle 22 is regarded as one nozzle. Further, Φ in Equation 5 is a function defined by Equation 1 above.

  Since the turbine 20b applies work to the compressor 20a, the energy conservation law does not hold in the turbine 20b, and the Bernoulli's theorem can not be applied to the turbine 20b. However, in the equation 5, if .mu..sub.Atb is expanded as one factor representing the gas flow ease, the equation 5 can be used as an equation representing the flow characteristic of the turbine 20b. The greater the turbine work, the less the gas passing through the turbine 20b loses energy and the less the gas flows. Therefore, if μAtb is a coefficient representing the ease of gas flow, the turbine work can be converted to μAtb, so equation 5 can represent the flow characteristics of the turbine 20b. In addition, since μAtb in Equation 5 corresponds to the effective opening area when the whole of the turbine 20b including the variable nozzle 22 is regarded as one nozzle, this is referred to as a turbine effective opening area in the present specification.

  The parameters that determine the turbine effective opening area are the degree of closure of the variable nozzle 22 provided in the turbine 20b and the flow rate through the turbine. The degree of closure of the variable nozzle 22 is a parameter indicating how close the variable nozzle 22 is closed based on the fully open position of the variable nozzle 22. The degree of closure when the variable nozzle 22 is in the fully open position is 0%, and the degree of closure when the variable nozzle 22 is in the fully closed position is 100%. FIG. 2 is a view showing the relationship between the degree of closure (θ vn) of the variable nozzle 22, the flow rate through the turbine (Mtb), and the turbine effective opening area (μAtb). FIG. 2 is an example of experimental results obtained using an experimental internal combustion engine. In the experiment, the turbine passing flow rate is fixed, and the value of the turbine effective opening area satisfying Equation 5 is calculated for each degree of closure of the variable nozzle 22 while changing the degree of closure of the variable nozzle 22 between 0% and 100%. It was done. Then, by repeating this operation while changing the flow rate through the turbine little by little from the large flow rate to the large flow rate, a characteristic diagram of the turbine effective opening area as shown in FIG. 2 was obtained.

2-2. Flow Characteristic Characteristic Formula of the EGR Device By the way, Bernoulli's theorem can be applied to the EGR valve 36 itself provided in the EGR device 30. However, when the state quantity at the inlet of the EGR passage 32 is used as the state quantity on the upstream side of the EGR valve 36, the energy conservation law which is the premise of Bernoulli's theorem does not hold due to the influence of the EGR cooler 34 interposed in the middle. . This is because the gas is deprived of heat in the EGR cooler 34. However, if μA egr is defined as one factor representing the ease of gas flow, as in the case of equation 5 representing the flow characteristics of the turbine 20 b, the state quantity at the inlet of the EGR passage 32 and the condition at the outlet of the EGR passage 32 The following equation 6 is established between the quantity. In Equation 6, Megr is the flow rate of the gas passing through the EGR valve 36, which is the flow rate through the EGR valve. Further, Φ in Equation 5 is a function defined by Equation 1 above. In addition, since μAegr in Equation 6 corresponds to the effective opening area when the whole of the EGR device 30 including the EGR valve 36 is regarded as one nozzle, in this specification, this is referred to as the EGR valve effective opening area. .

  The parameters that determine the EGR valve effective opening area are the opening degree of the EGR valve 36 and the EGR valve passing flow rate. FIG. 3 is a view showing the relationship between the opening degree (θegr) of the EGR valve 36, the EGR valve passing flow rate (Megr), and the EGR valve effective opening area (μAegr). FIG. 3 shows an example of experimental results obtained using an experimental internal combustion engine. In the experiment, while the EGR valve passing flow rate is fixed and the opening degree of the EGR valve 36 is changed between 0% and 100%, the value of the EGR valve effective opening area for which the formula 6 is satisfied is for each opening degree of the EGR valve 36 It was done to calculate. Then, by repeatedly performing this operation while changing the EGR valve passing flow rate little by little from the large flow rate to the large flow rate, a characteristic diagram of the EGR valve effective opening area as shown in FIG. 3 was obtained.

  The characteristic shown in FIG. 3 is the characteristic of the EGR valve effective opening area when the bypass valve 40 is closed. When the bypass valve 40 is open, the EGR cooler 34 does not take heat from the gas. For this reason, even if the EGR valve opening degree and the EGR valve passage flow rate are the same, the value of the EGR valve effective opening area for which the equation 6 holds is different from that in the case where the bypass valve 40 is closed. A separate experiment is performed for the case where the bypass valve 40 is open, and a characteristic diagram different from FIG. 3 is obtained.

2-3. Simplification of the Function Φ The function Φ included in the above Equations 5 and 6 is a complex function having the pressure ratio π between the downstream pressure and the upstream pressure of the nozzle as a variable as shown in the above Equation 1 is there. However, according to the piecewise linear method, the function を can be divided into a plurality of pressure ratio π sections, and simplification can be made by linearly approximating each section of the pressure ratio π with a linear function. FIG. 4 is a diagram showing the relationship between the function Φ and the pressure π which is its variable. A curve indicated by a broken line indicates the relationship between the function Φ represented by the equation 1 and the pressure π, and a broken line indicated by a solid line indicates a relationship between the function し た and the pressure π which are linearly approximated by the piecewise linear method. In the example shown in FIG. 4, the pressure ratio π is divided into six sections, and the function Φ is approximated by a straight line for each section.

The function Φ included in Equation 5 can be simplified as in Equation 2 above by the piecewise linear method. By using the simplified function Φ, the flow rate characteristic of the turbine 20b can be expressed by the following equation 7. The values of the coefficients a and b in Equation 7 are determined for each pressure ratio division. The values of the coefficients a and b corresponding to the section defined by the value of the ratio of the turbine downstream pressure (Pds) to the turbine upstream pressure (Pus) are substituted into the equation (7). However, as for the turbine upstream pressure (Pus), the previous value calculated at the previous calculation timing is used.

The function Φ included in Equation 6 can be simplified as in Equation 3 above by the piecewise linear method. By using the simplified function Φ, the flow rate characteristic of the EGR device 30 can be expressed by the following equation 8. The values of the coefficients c and d in Equation 8 are determined for each pressure ratio division. The values of the coefficients c and d corresponding to the section defined by the value of the ratio of the intake manifold pressure (Pim) to the pressure upstream of the turbine (Pus) are substituted into the equation (8). However, as for the turbine upstream pressure (Pus), the previous value calculated at the previous calculation timing is used.

2-4. Integration of the flow rate characteristic equation In the above equation 7, Tus can be measured by the temperature sensor 56, and Pds can be measured by the pressure sensor 58. Further, Mtb can be calculated from the amount of fresh air (Gadly) measured by the air flow sensor 50 and the fuel flow rate (Gf) of the fuel injected from the fuel injection valve 6 into the cylinder. μAtb is determined based on the degree of closure (θvn) of the variable nozzle 22 and the flow rate through the turbine (Mtb). Therefore, by rearranging Equation 7 with respect to Pus, an equation for calculating Pus can be obtained from Tus, Pds, Mtb and μAtb. That is, Equation 7 can be used to simply estimate the pressure upstream of the turbine.

  However, noise tends to get on the measurement value of the air flow sensor 50. Since the turbine passing flow rate (Mtb) is calculated from the fresh air amount measured by the air flow sensor 50, the noise included in the fresh air amount will be directly on the calculated value of the turbine passing flow rate. Therefore, the estimated value of the turbine upstream pressure calculated using Equation 7 is affected by the noise of the air flow sensor 50 and can not necessarily be said to have high accuracy.

Therefore, attention is paid to the relationship shown in the following equation 9. The sum of the flow rate through the turbine (Mtb) and the flow rate through the EGR valve (Megr) corresponds to the total flow rate of the exhaust from the engine body 4 to the exhaust passage 10, which corresponds to the in-cylinder gas amount (Gcyl) and the fuel flow rate It is represented by the sum of Gf). The in-cylinder gas amount can be calculated using a state equation based on the intake manifold pressure (Pim) measured by the pressure sensor 52 and the intake manifold temperature (Tim) measured by the temperature sensor 54. The fuel flow rate can be calculated from the command value given from the control device 100 to the fuel injection valve 6.

Unlike the air flow sensor 50, the pressure sensor 52 and the temperature sensor 54 are difficult for noise to get on. Therefore, according to the right side of equation 9, it is possible to obtain the total flow rate of the exhaust with higher accuracy than the left side. By substituting the right side of equation 7 into Mtb on the left side of equation 9 and substituting the right side of equation 8 into Megr on the left side of equation 9, the following equation 10 is obtained. By arranging this equation 10 for Pus, the above equation 4 can be obtained.

  In order to verify the estimation accuracy of the turbine upstream pressure according to Equation 4, verification data was obtained for various fuel injection amounts and various engine rotational speeds as shown in FIG. The verification data consists of the estimated value of the turbine upstream pressure according to Equation 4 and the actual value of the turbine upstream pressure. FIG. 6 is a graph in which the data for verification is plotted on a plane in which the estimated value (estimated Pus) of the turbine upstream pressure is taken on the vertical axis and the actual value (actual Pus) of the turbine upstream pressure is taken on the abscissa. As shown in this graph, the degree of agreement between the estimated value of the turbine upstream pressure according to Equation 4 and the actual value is high. From this, it is understood that the turbine upstream pressure can be accurately calculated by using the equation (4).

  Note that the noise of the air flow sensor 50 affects the calculation results of μAtb and μAegr in Expression 4. This is because μAtb is calculated based on the flow rate through the turbine (Mtb), and μAegr is calculated based on the flow rate through the EGR valve (Megr). However, in view of the relationship between μAtb and Mtb shown in FIG. 2, the sensitivity of μAtb to the variation of Mtb is not very high. Similarly, in view of the relationship between μAegr and Megr shown in FIG. 3, the sensitivity of μAegr to the variation of Megr is not very high. Therefore, the influence of the noise of the air flow sensor 50 on the calculation results of μAtb and μAegr is limited, and it can be said that the calculation accuracy of the turbine upstream pressure including μAtb and μAegr as parameters is sufficiently secured.

3. Configuration and Operation of Control Device FIG. 7 is a block diagram showing a configuration for calculating the pressure upstream of the turbine that the control device 100 has. As a result of the CPU upstream pressure estimation program stored in the ROM being executed by the CPU, the control device 100 operates as the arithmetic units 102, 104, 106, 108 and 110 shown in FIG.

  When the turbine upstream pressure estimation program is executed, the controller 100 controls the current value Pds of the turbine downstream pressure, the current value Pim of the intake manifold pressure, the current value Tus of the turbine upstream temperature, and the current value θegr of the opening degree of the EGR valve 36. The current value θvn of the closing degree of the variable nozzle 22 and the current value Gadly of the fresh air amount are acquired from the corresponding sensors at predetermined control cycles.

  In addition, when the turbine upstream pressure estimation program is executed, the control device 100 controls the present value Gcyl of the in-cylinder gas amount, the present value Gf of the fuel flow, the present value Mtb of the turbine passing flow, and the current of the EGR valve passing flow The value Megr is calculated in each predetermined control cycle. The current value Mtb of the turbine passing flow rate is calculated from the current value Gadly of the fresh air amount and the current value Gf of the fuel flow rate. The current value Megr of the EGR valve passing flow rate is calculated from the difference between the sum of the current value Gcyl of the in-cylinder gas amount and the current value Gf of the fuel flow rate and the current value Mtb of the turbine passing flow rate.

  Further, control device 100 temporarily stores, in the RAM, the previous value Pus_0 of the turbine upstream pressure calculated by calculation unit 110 described later in a predetermined control cycle.

  The ROM of the control device 100 stores a first coefficient map that associates the coefficients a and b of the linear function shown in Equation 2 with the sections of the pressure ratio π. When the ratio between the current value Pds of the turbine downstream pressure and the previous value Pus_0 of the turbine upstream pressure is a pressure ratio π, the arithmetic unit 102 sets each coefficient a, b corresponding to a section to which the pressure ratio π applies to a first coefficient It is configured to read from the map.

  The ROM of the control device 100 stores a second coefficient map that associates the coefficients c and d of the linear function shown in Equation 3 with the sections of the pressure ratio π. When the ratio of the current value Pim of the intake manifold pressure to the previous value Pus_0 of the turbine upstream pressure is a pressure ratio π, the arithmetic unit 104 sets each coefficient c, d corresponding to a section to which the pressure ratio π is a second coefficient It is configured to read from the map.

  The ROM of the control device 100 stores a turbine effective opening area map in which the relationship between the degree of closure of the variable nozzle 22 shown in FIG. 2, the flow rate through the turbine, and the turbine effective opening area is mapped. The arithmetic unit 106 is configured to read out the turbine effective opening area μAtb corresponding to the current value Mtb of the flow rate through the turbine and the current value θvn of the degree of closure of the variable nozzle 22 from the turbine effective opening area map.

  The ROM of the control device 100 stores a turbine effective opening area map in which the relationship between the opening degree of the EGR valve 36 and the EGR valve passing flow rate and the EGR valve effective opening area shown in FIG. 3 is mapped. The arithmetic unit 108 is configured to read out the EGR valve effective opening area μAegr corresponding to the current value Megr of the EGR valve passing flow rate and the current value θegr of the opening degree of the EGR valve 36 from the EGR valve effective opening area map.

  The arithmetic unit 110 sums the present value Pds of the downstream pressure of the turbine, the present value Pim of the intake manifold pressure, the present value Tus of the upstream temperature of the turbine, the present value Gcyl of the in-cylinder gas amount and the present value Gf of the fuel flow rate. The present value (estimated value) Pus of the turbine upstream pressure is calculated using Equation 4 on the basis of the turbine effective opening area μAtb, the EGR valve effective opening area μAegr, and the coefficients a, b, c, d. Is configured as.

4. Applications of estimated values of turbine upstream pressure There are various applications of estimated values of turbine upstream pressure calculated using Equation 4. Here, typical applications among the applications of estimated values of turbine upstream pressure are introduced.

  The first application of turbine upstream pressure estimates is to estimate the EGR rate. Control device 100 includes an EGR rate estimation model shown in FIG. The EGR rate estimation model is based on the turbine upstream pressure (Pus), the fuel injection amount (Q), the intake manifold pressure (Pim), the fresh air amount (Gadly), the engine water temperature (Tw), and the intake air temperature (Tair). It is configured to calculate an estimated value. The estimated value of the EGR rate is used as one of the control parameters of the internal combustion engine 2 by the control device 100.

  A second application of turbine upstream pressure estimates is the suppression of torque steps that occur when switching between combustion modes. When the catalyst is inactive, switching of the combustion mode from the normal combustion mode to the rich combustion mode may be performed in order to raise the exhaust temperature to activate the catalyst. In the rich combustion mode, the opening of the intake throttle valve 16 is throttled to reduce the amount of air, thereby enriching the air-fuel ratio. However, when the normal combustion mode is switched to the rich combustion mode, the intake throttle valve 16 is throttled to increase the pump loss of the internal combustion engine 2. Therefore, as shown in FIG. 9, the control device 100 calculates the pump loss based on the turbine upstream pressure (Pus) and the intake manifold pressure (Pim), and calculates the injection correction amount according to the size of the pump loss. Then, by adding the injection correction amount to the injection amount calculated from the required torque, the torque step caused by the increase of the pump loss is suppressed.

  A third application of turbine upstream pressure estimates is the detection of the possibility of EGR gas backflow. When the intake manifold pressure is higher than the pressure upstream of the turbine, EGR gas may flow back through the EGR passage 32. The controller 100 detects the possibility of backflow of the EGR gas by comparing the estimated value of the turbine upstream pressure with the measured value of the intake manifold pressure. Even when the internal combustion engine 2 is operated in the operating range where the EGR valve 36 is opened, the control device 100 keeps the EGR valve 36 closed until there is no risk of backflow of the EGR gas.

  A fourth application of the estimate of turbine upstream pressure is the detection of the possibility of a hard failure of the internal combustion engine 2. The control device 100 monitors the estimated value of the turbine upstream pressure, and performs supercharging pressure control and EGR ratio control so that the turbine upstream pressure does not exceed a predetermined safety reference value.

2 internal combustion engine 4 engine main body 4a cylinder 6 fuel injection valve 8 intake passage 10 exhaust passage 20 turbo supercharger 20a compressor 20b turbine 22 variable nozzle 30 EGR device 32 EGR passage 36 EGR valve 50 air flow sensors 52, 58 pressure sensors 54, 56 Temperature sensor 100 controller

Claims (1)

A control device for an internal combustion engine, comprising: a turbocharger having a variable nozzle in a turbine; and an EGR device having an EGR passage connected upstream of the turbine in the exhaust passage and an intake passage and having an EGR valve in the EGR passage.
A means for acquiring a current value P ds of turbine downstream pressure, which is the pressure in the exhaust passage on the outlet side of the turbine;
A means for acquiring a current value Pim of an intake passage pressure which is a pressure in a space to which the EGR passage of the intake passage is connected;
A means for obtaining a current value Tus of a turbine upstream temperature, which is a temperature in an exhaust passage on the inlet side of the turbine;
A means for acquiring a current value θegr of the opening degree of the EGR valve;
A means for acquiring a current value θvn of the closing degree of the variable nozzle;
A means for acquiring a current value Gadly of a fresh air amount which is a flow rate of fresh air taken into the intake passage;
A means for calculating the current value Gcyl of the gas amount in the cylinder from the pressure and temperature of the gas entering the cylinder;
A means for calculating a current value Gf of the fuel flow rate of the fuel injection valve;
A means for calculating a current value Mtb of a flow rate through a turbine which is a flow rate of gas passing through the turbine from the current value Gadly of the fresh air amount and the current value Gf of the fuel flow rate;
A means for calculating a current value Megr of an EGR valve passing flow rate from a difference between a current value Gcyl of the in-cylinder gas amount and a current value Gf of the fuel flow rate and a current value Mtb of the turbine passing flow rate;
A means for storing a previous value Pus_0 of the turbine upstream pressure, which is the pressure in the exhaust passage on the inlet side of the turbine;
A means for storing in advance a turbine effective opening area map relating a turbine effective opening area when the whole of the turbine including the variable nozzle is regarded as one nozzle to a turbine flow rate and the closing degree of the variable nozzle;
A means for reading from the turbine effective opening area map a turbine effective opening area μAtb corresponding to the current value Mtb of the flow rate through the turbine and the current value θvn of the degree of closure of the variable nozzle;
Means for storing in advance an EGR valve effective opening area map which relates the EGR valve effective opening area when the whole of the EGR device including the EGR valve is regarded as one nozzle to the EGR valve passing flow rate and the opening degree of the EGR valve When,
A means for reading out an EGR valve effective opening area μAegr corresponding to the current value Megr of the EGR valve passing flow rate and the current value θegr of the opening degree of the EGR valve from the EGR valve effective opening area map;
The function Φ of the pressure ratio π between the downstream pressure and the upstream pressure of the nozzle defined by the following equation 1 is divided into a plurality of pressure ratios π by the piecewise linear method, and Means for pre-storing a first coefficient map relating each coefficient a, b of the linear function determined for each section of the pressure ratio π to a section for the pressure ratio π when linear approximation is performed by the linear function defined by the equation 2 When,
When the ratio of the current value P ds of the turbine downstream pressure to the previous value P u s of the turbine upstream pressure is the pressure ratio π in the equation 2, the coefficients a and b corresponding to the sections to which the pressure ratio Means for reading out from one coefficient map,
The function Φ of the pressure ratio π between the downstream pressure and the upstream pressure of the nozzle defined by the equation 1 is divided into a plurality of pressure ratio π segments by the piecewise linear method, and the following equation is provided for each pressure ratio π segment Means for pre-storing a second coefficient map relating each coefficient c, d of the linear function determined for each section of the pressure ratio π to a section of the pressure ratio π when linear approximation is performed by the linear function defined in 3; ,
When the ratio of the current value Pim of the intake passage pressure to the previous value Pus_0 of the turbine upstream pressure is the pressure ratio π in the equation 3, the coefficients c and d corresponding to the sections to which the pressure ratio π applies are Means for reading out from the 2 coefficient map
The sum of the present value Pds of the turbine downstream pressure, the present value Pim of the intake passage pressure, the present value Tus of the turbine upstream temperature, the present value Gcyl of the in-cylinder gas amount, and the present value Gf of the fuel flow Based on the turbine effective opening area μAtb, the EGR valve effective opening area μAegr, and the coefficients a, b, c, and d, the current value Pus of the turbine upstream pressure is calculated using Equation 4 below. Means to calculate,
A means for controlling the internal combustion engine based on a current value Pus of the turbine upstream pressure;
A control device for an internal combustion engine, comprising:

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