JP4583943B2 - Supercharging pressure control device for internal combustion engine - Google Patents

Description

  The present invention relates to a supercharging pressure control device for an internal combustion engine equipped with a turbocharger.

  A compressor wheel that pressurizes air sucked into the internal combustion engine, a turbine wheel that is connected to the compressor wheel and is rotationally driven by the kinetic energy of the exhaust gas, and is opened and closed to change the flow rate of the exhaust gas blown to the turbine wheel Variable capacity turbochargers having a variable vane to be driven are widely known.

  In order to reduce NOx contained in the exhaust gas, an internal combustion engine provided with an exhaust gas recirculation mechanism that recirculates the exhaust gas to the intake system is also widely used. The exhaust gas recirculation mechanism is provided with an exhaust gas recirculation valve that controls the exhaust gas recirculation amount, and the change in the opening degree of the exhaust gas recirculation valve depends on the pressure of exhaust gas supplied to the turbine wheel (exhaust pressure on the upstream side of the turbine wheel) and Affects supercharging pressure.

  Patent Document 1 discloses a control method for controlling the opening degree of an exhaust gas recirculation valve and a variable vane of a turbocharger using a combustion model of an internal combustion engine. According to this method, the change in the intake air flow rate according to the control amount for controlling the opening degree of the exhaust gas recirculation valve is input to the supercharging pressure control unit, and the variable vane opening degree is adjusted according to the exhaust gas recirculation amount. Is called.

Special table 2003-529716 gazette

  In the control method disclosed in Patent Document 1, in order to input the control amount of the exhaust gas recirculation valve to the supercharging pressure control unit, compensation processing (block 140 in FIG. 2) for improving transient characteristics, and the exhaust gas recirculation valve Therefore, there is a problem that the process of converting the control amount into a change in the intake air flow rate (block 142 in FIG. 2) complicates the configuration of the control system.

  The present invention has been made paying attention to this point, and provides a supercharging pressure control device capable of performing supercharging pressure control with good responsiveness according to the exhaust gas recirculation amount by a control system having a relatively simple configuration. The purpose is to provide.

In order to achieve the above object, an invention according to claim 1 is directed to a compressor wheel (15) that pressurizes air sucked into an internal combustion engine (1), and the compressor wheel (15) connected to the exhaust gas of the engine. A turbocharger (8) having a turbine wheel (10) that is rotationally driven by the kinetic energy, exhaust gas flow rate varying means (12) for changing the flow rate of exhaust gas blown to the turbine wheel (10), In a supercharging pressure control device for an internal combustion engine comprising an exhaust gas recirculation mechanism (5, 6) for recirculating exhaust gas from an upstream side of a turbine wheel (10) to an intake system, the exhaust gas is controlled based on an operating state of the engine. The lift amount command value (LCMD) of the exhaust gas recirculation valve (6) for controlling the exhaust gas recirculation amount passing through the recirculation mechanism is calculated, and the lift amount of the exhaust gas recirculation valve is calculated. The lift amount command value LACT) (EGR controller for controlling so as to coincide with LCMD) and (33), the upstream side exhaust pressure detecting means for detecting an upstream side of the exhaust pressure (P3) of the turbine wheel (10) (23) and an upstream exhaust pressure (P3) detected by the upstream exhaust pressure detection means based on a control target model that models a control target from the intake system to the exhaust system of the engine is a target exhaust pressure. (P3CMDF) is provided with control means for controlling the exhaust gas flow rate variable means (12), and the control target model has an operation amount (VO) of the exhaust gas flow rate variable means (12) as a control input. the first model parameter (b) to be multiplied by) are defined by using the second model parameter indicating the disturbance applied to the controlled object (c), the second model parameter (c But Ri function der the exhaust gas recirculation amount (m _r dot) that passes through the exhaust gas recirculation mechanism, wherein the control means comprises identification means for identifying the first and second model parameters (b, c), The control is performed using the identified model parameter .

The invention according to claim 2, in the supercharging pressure control device according to claim 1, wherein said control means, and performs the control with the sliding mode control using the model parameters identified.

A third aspect of the present invention is the supercharging pressure control device according to the first or second aspect , further comprising a supercharging pressure detecting means (22) for detecting a supercharging pressure (P2), wherein the control means comprises: The target boost pressure setting means for setting the target boost pressure (P2CMD) according to the operating state of the engine, and the detected boost pressure (P2) match the target boost pressure (P2CMD). And target upstream exhaust pressure setting means for setting the target upstream exhaust pressure (P3CMD).

According to a fourth aspect of the present invention, in the supercharging pressure control device according to any one of the first to third aspects, a downstream side exhaust pressure detecting means for detecting an exhaust pressure (P4) downstream of the turbine wheel. (26), wherein the control means prevents the pressure ratio (PR = P3 / P4) of the upstream exhaust pressure (P3) to the downstream exhaust pressure (P4) from exceeding a predetermined pressure ratio (PR0). Further, the exhaust gas flow rate varying means (12) is controlled.

Specifically, the target upstream exhaust pressure setting means calculates an upstream limit value (P3LMT) by multiplying the detected downstream exhaust pressure (P4) by the predetermined pressure ratio (PR0), It is desirable to set the target upstream exhaust pressure (P3CMDF) so as not to exceed the upstream limit value (P3LMT).
The exhaust gas flow rate varying means is preferably a variable vane that is driven to open and close to change the flow rate of the exhaust gas blown to the turbine wheel.

According to the first aspect of the present invention, based on the controlled object model that models the controlled object from the intake system to the exhaust system of the engine, the detected upstream exhaust pressure matches the target exhaust pressure. The exhaust gas flow rate variable means is controlled. The controlled object model is defined using a first model parameter that is multiplied by an operation amount of the exhaust gas flow rate varying means that is a control input, and a second model parameter that indicates a disturbance applied to the controlled object. Since the parameter is a function of the exhaust gas recirculation amount passing through the exhaust gas recirculation mechanism, the second model parameter that is a function of the exhaust gas recirculation amount is identified, and the exhaust gas return is obtained by using the identified model parameter. Exhaust pressure control and supercharging pressure control are performed in consideration of the influence of the flow rate. Therefore, it is possible to perform supercharging pressure control with good responsiveness according to the exhaust gas recirculation amount with a relatively simple configuration. In addition, since the control target model uses the operation amount of the exhaust gas flow rate varying means as the control input and the exhaust pressure upstream of the turbine wheel as the control output, the upstream exhaust pressure can be quickly adjusted based on the control target model. To the target upstream exhaust pressure.

According to the second aspect of the present invention, the operation amount of the exhaust gas flow rate varying means is controlled by the sliding mode control using the identified model parameter. Since the sliding mode control has robustness capable of obtaining a relatively good control characteristic even if there is a modeling error (difference between the characteristic of the actual controlled object and the characteristic of the controlled object model), for example, the control system Good controllability can be obtained even if a controlled object model having a dead time of “0” is used.

According to the third aspect of the invention, the target boost pressure is set according to the engine operating state, and the target upstream exhaust pressure is set so that the detected boost pressure matches the target boost pressure. The operation amount of the exhaust gas flow rate varying means is controlled so that the detected upstream exhaust pressure matches the target upstream exhaust pressure. Thus, by adopting cascade control including two feedback controls, control performance can be improved.

According to the fourth aspect of the present invention, the exhaust gas flow rate varying means is controlled so that the pressure ratio of the upstream exhaust pressure to the downstream exhaust pressure does not exceed the predetermined pressure ratio. Generally, when the pressure ratio of the upstream exhaust pressure to the downstream exhaust pressure increases, the mass flow rate of exhaust gas that drives the turbine wheel (hereinafter simply referred to as “turbine passing exhaust gas flow rate”) increases, but the exhaust gas flow rate increases. When the pressure ratio PR0 reaching the speed of sound is exceeded, it hardly increases. Therefore, by setting the predetermined pressure ratio in the vicinity of the pressure ratio PR0, for example, when the engine is accelerated, the exhaust gas flow rate through the turbine is rapidly increased without excessively increasing the upstream exhaust pressure, and the supercharging pressure is quickly increased. Can be increased.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 9 is provided in each cylinder. The fuel injection valve 9 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening time of the fuel injection valve 9 is controlled by the ECU 20.

  The engine 1 includes an intake pipe 2, an exhaust pipe 4, and a turbocharger 8. The turbocharger 8 includes a turbine 11 having a turbine wheel 10 that is rotationally driven by the kinetic energy of exhaust, and a compressor 16 having a compressor wheel 15 connected to the turbine wheel 10 via a shaft 14. The compressor wheel 15 pressurizes (compresses) air sucked into the engine 1.

  The turbine 11 includes a plurality of variable vanes 12 (only two are shown) that are driven to open and close to change the flow rate of exhaust gas blown to the turbine wheel 10 and an actuator (not shown) that drives the variable vanes to open and close. By changing the opening VO of the variable vane 12 (hereinafter referred to as “vane opening”), the flow rate of the exhaust gas blown to the turbine wheel 10 can be changed, and the rotational speed of the turbine wheel 10 can be changed. It is configured. The actuator that drives the variable vane 12 is connected to the ECU 20, and the vane opening VO is controlled by the ECU 20. More specifically, the ECU 20 supplies a control signal with a variable duty ratio to the actuator, thereby controlling the vane opening VO. The configuration of a turbocharger having a variable vane is widely known, and is disclosed in, for example, Japanese Patent Laid-Open No. 1-208501.

  Between the exhaust pipe 4 and the intake pipe 2, an exhaust gas recirculation passage 5 that circulates exhaust gas to the intake pipe 2 is provided. The exhaust gas recirculation passage 5 is provided with an exhaust gas recirculation valve (hereinafter referred to as “EGR valve”) 6 for controlling the exhaust gas recirculation amount. The EGR valve 6 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 20. The EGR valve 6 is provided with a lift sensor 7 for detecting the valve opening degree (valve lift amount) LACT, and the detection signal is supplied to the ECU 20. An exhaust gas recirculation mechanism is configured by the exhaust gas recirculation passage 5 and the EGR valve 6.

  The intake pipe 2 includes an intake air flow rate sensor 21 that detects an intake air flow rate GA, a boost pressure sensor 22 that detects an intake pressure (supercharge pressure) P2 on the downstream side of the compressor 16, and an intake air pressure Ti that detects an intake air temperature Ti. An air temperature sensor 23 is provided. Further, the exhaust pipe 4 detects an exhaust temperature sensor 24 that detects the exhaust temperature Te, an upstream exhaust pressure sensor 25 that detects an exhaust pressure P3 upstream of the turbine 11, and an exhaust pressure P4 that is downstream of the turbine 11. A downstream exhaust pressure sensor 26 is provided. These sensors 21 to 26 are connected to the ECU 20, and detection signals of the sensors 21 to 26 are supplied to the ECU 20.

A particulate matter filter (hereinafter referred to as “DPF”) 17 that collects particulate matter (mainly composed of soot) contained in the exhaust gas is provided on the exhaust pipe 4 downstream of the downstream exhaust pressure sensor 26. It has been.
An accelerator sensor 27 that detects a depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of an accelerator pedal (not shown) of a vehicle driven by the engine 1 and an engine rotation that detects an engine speed (rotation speed) NE. A number sensor 28 is connected to the ECU 20, and detection signals from these sensors are supplied to the ECU 20.

  The ECU 20 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit for storing various calculation programs executed by the CPU and calculation results, an actuator for driving the variable vane 12 of the turbine 11, an output circuit for supplying a drive signal to the fuel injection valve 9, the EGR valve 6, etc. Consists of

  The ECU 20 calculates the basic fuel amount TI (specifically, the valve opening time of the fuel injection valve 9) in accordance with the operating state of the engine 1, specifically, the required torque corresponding to the accelerator pedal operation amount AP, and the basic fuel amount is calculated. The target boost pressure P2CMD is calculated according to the amount TI and the engine speed NE, and the boost pressure control for controlling the vane opening degree VO is performed so that the detected boost pressure P2 coincides with the target boost pressure P2CMD. . Further, the ECU 20 sets a target intake air flow rate GACMD according to the basic fuel amount TI and the engine speed NE, and lifts the EGR valve 6 according to the deviation between the target intake air flow rate GACMD and the detected intake air flow rate GA. An amount (valve opening) command value LCMD is calculated.

  In the present embodiment, the target upstream exhaust pressure P3CMD is first set so that the detected boost pressure P2 matches the target boost pressure P2CMD, and then the detected upstream exhaust pressure P3 is set as the target upstream exhaust pressure P3CMD. The vane opening degree VO is controlled so as to coincide with. More specifically, a control target model that models from the intake system of the engine 1 to the exhaust system through the cylinder is defined, and the upstream exhaust pressure P3 is changed to the target upstream exhaust pressure by sliding mode control based on the control target model. The vane opening degree VO is controlled to coincide with the atmospheric pressure P3CMD. Therefore, a mathematical expression that defines the controlled object model will be described first, and then identification of model parameters included in the mathematical expression and sliding mode control using the identified model parameters will be described.

[Controlled model]
FIG. 2 is a diagram schematically showing a control target from the intake pipe 2 of the engine 1 to the exhaust pipe 4 through the cylinder 1a. In this figure, m _c dot is the intake air flow rate (compressor passing air flow rate), P2 is the supercharging pressure, Vi is the volume downstream of the compressor 16 in the intake pipe 2, and m _z dot is the air flow rate flowing into the cylinder 1a ( Ti is the intake air temperature (° K), m _f dot is the flow rate of the fuel injected into the cylinder (hereinafter referred to as “fuel flow rate”), and P3 is the exhaust upstream of the turbine 11. Atmospheric pressure, Ve is the upstream volume of the exhaust pipe 4 from the turbine 11, Te is the exhaust temperature (° K), m _r dot is the exhaust gas recirculation amount, m _tb dot is the flow rate of exhaust gas passing through the turbine 11 (hereinafter “turbine” It is referred to as “passing gas flow rate”. All the flow rates are mass flow rates [kg / s]. When the state parameters are defined in this way, the time differential value (hereinafter referred to as “exhaust pressure differential value”) P3dot of the upstream side exhaust pressure P3 is given by the following equations (1) and (2). The time differential value (hereinafter referred to as “supercharging pressure differential value”) P2dot of the supercharging pressure P2 is given by the following equations (3) and (4).

_{P3dot = k e (m z dot} + m f dot-m r dot-m tb dot) (1)
k _e = nRTe / Ve (2)
_{P2dot = k i (m c dot} + m r dot-m z dot) (3)
k _i = nRTi / Vi (4)
Here, n is a polytropic index and R is a gas constant.

The following formula (5) is obtained from the formulas (1) and (3). When the exhaust pressure differential value P3dot is obtained from the equation (5), the following equation (6) is obtained.

Further, the turbine passing gas flow rate m _tb dot is calculated by the following equation (7) by regarding the turbine 11 as a nozzle.
m _tb dot = Atb (VO) · U (P3) · Φ (P4 / P3) (7)

  Here, Atb is a turbine effective opening area defined as a function of the vane opening VO, U (P3) is an upstream condition function calculated by the following equation (8), and Φ (P4 / P3) is , A pressure function given by the following equations (9) and (10). P3 and P4 are an upstream exhaust pressure and a downstream exhaust pressure, respectively. Ρ in equation (8) is the density of exhaust gas passing through the turbine 11, and κ in equations (9) and (10) is the specific heat ratio of exhaust gas passing through the nozzle. When the exhaust gas flow velocity is lower than the sonic velocity, the equation (9) is applied, and when the exhaust gas flow velocity is equal to or higher than the sonic velocity, the equation (10) is applied.

ここでタービン有効開口面積Ａtb（ＶＯ）を制御入力ｕとし、上流側排気圧Ｐ３を制御出力ｘとし、連続系の制御対象モデルを下記式（１２）で定義する。
ｘdot＝ａ_c・ｘ＋ｂ_c・ｕ＋ｃ_c （１２） By applying Expression (7) to Expression (6), the following Expression (11) is obtained.

Here, the turbine effective opening area Atb (VO) is set as the control input u, the upstream exhaust pressure P3 is set as the control output x, and the continuous control target model is defined by the following equation (12).
_{xdot = a c · x + b} c · u + c c (12)

Here, xdot is the time differential value of the control output _{x, a c, b c,} c c is a model parameter of a continuous system. When Expression (12) is compared with Expression (11), model parameters a _c , b _c , and _cc are as follows.
a _c = 0 (13)
_{b c = -k e · U (} P3) · Φ (P3 / P4) (14)
_{c c = k e (m c} dot + m f dot-P2dot / k i) (15)

Next, when Expression (12) is discretized using Pad approximation, the following Expression (16) is obtained. “K” in Expression (16) is a discretized control time.
x (k + 1) = a (k) .x (k) + b (k) u (k) + c (k) (16)

Here the model parameters a, b, c the following formulas model parameters a _c of the continuous time system, b _c, a c _c (17), (18), is calculated by applying the (19). In the following formulas (17), (18), and (19), h is a sampling period.

Here, since the continuous model parameter a _c is “0” (equation (13)), the model parameters a, b, and c are as follows.
a = 1 (20)
_{b = h · b c = -h} · k e · U (P3) · Φ (P3 / P4) (21)
_{c = h · c c = h} · k e (m c dot + m f dot-P2dot / k i) (22)

Here, the intake air flow rate m _c dot and supercharge pressure derivative value P2dot varies depending on the exhaust gas recirculation amount m _r dot, i.e. a function of the exhaust gas recirculation amount m _r dot. Thus, the model parameters c indicating a disturbance applied to the controlled object, using a controlled object model which is a function of the exhaust gas recirculation amount m _r dot, by identifying the model parameter c in real time, the exhaust gas recirculation amount m _r dot Exhaust pressure control and supercharging pressure control are performed in consideration of the effects of the above. Therefore, it is possible to perform supercharging pressure control with good responsiveness according to the exhaust gas recirculation amount with a relatively simple configuration.

[Identification of model parameters]
In the present embodiment, since the model parameter a is always “1”, the equation (16) becomes the following equation (16a).
x (k + 1) = x (k) + b (k) u (k) + c (k) (16a)

The model parameters calculated by the equations (21) and (22) are set as the reference model parameters b _base and c _base , respectively. The model parameter b (k) is always set to the reference model parameter b _base and the model parameter c (k ) Is calculated by performing a sequential identification error calculation using the following equation (31). Δc (k) in equation (31) is an update component of the reference model parameter c _base calculated by equation (32), Kid in equation (32) is the identification gain, and eid (k) is calculated by equation (33). Identification error. Further, xhat (k) in Expression (33) is an estimated value of the control output x (upstream exhaust pressure P3) calculated by Expression (34).

c (k) = c _base (k) + δc (k) (31)
δc (k) = δc (k−1) + (Kid / (1 + Kid)) · eid (k) (32)
eid (k) = x (k) −xhat (k) (33)
xhat (k) = x (k-1) + b (k-1) u (k-1) + c (k-1) (34)

[Calculation of control input by sliding mode control]
The switching function value σ (k) in the sliding mode control is defined by the following equation (41). E (k) in the equation (41) is a control deviation calculated by the following equation (42), and x _cmd (k) in the equation (42) is a control target value. Further, s in the equation (41) is a switching function setting parameter that determines the attenuation characteristic of the control deviation e (k), and is set to a value larger than −1 and smaller than 1.
σ (k) = e (k) + s · e (k−1) (41)
e (k) = x (k) −x _cmd (k) (42)

  On the phase plane where the vertical axis is defined as the control deviation e (k) and the horizontal axis is defined as the previous control deviation e (k-1), the control deviation e (k) satisfying σ (k) = 0 and the previous control Since the combination with the deviation e (k-1) is a straight line, this straight line is generally called a switching straight line. The sliding mode control is a control that pays attention to the behavior of the control deviation e (k) on the switching line so that the switching function value σ (k) becomes 0, that is, the control deviation e (k) and the previous control deviation. Control is performed so that the combination of e (k-1) is placed on the switching line on the phase plane, thereby realizing robust control against disturbances and modeling errors. As a result, the control output, that is, the upstream exhaust pressure P3 is controlled with good robustness so as to follow the target upstream exhaust pressure P3CMD.

  Further, by changing the value of the switching function setting parameter s in the equation (41), the damping characteristic of the control deviation e (k), that is, the follow-up characteristic of the upstream exhaust pressure P3 to the target upstream exhaust pressure P3CMD is changed. Can do. Specifically, when s = −1, the characteristic does not follow at all, and the follow-up speed can be increased as the absolute value of the switching function setting parameter s is reduced.

  In sliding mode control, the control deviation e (k) is specified by constraining the combination of the control deviation e (k) and the previous control deviation e (k-1) (hereinafter referred to as "deviation state quantity") on the switching line. Convergence to zero with robust convergence speed and robust against disturbances and modeling errors. Therefore, in the sliding mode control, it is important how to put the deviation state quantity on the switching straight line and restrain it there.

From such a viewpoint, the control input (controller output) u (k) is calculated as the sum of the equivalent control input Ueq (k) and the reaching law input Urch (k) as shown in the following equation (43). .
u (k) = Ueq (k) + Urch (k) (43)
Here, Ueq (k) is an input for constraining the deviation state quantity on the switching line, and the reaching law input Urch (k) is an input for placing the deviation state quantity on the switching line. A method for calculating each input Ueq (k) and Urch (k) will be described below.

Since the equivalent control input Ueq (k) is an input for constraining the deviation state quantity on the switching straight line, the condition to be satisfied is given by the following equation (44).
σ (k) = σ (k + 1) (44)
When the control input u (k) satisfying the equation (44) is obtained using the equation (16a) and the equations (41) and (42), the following equation (45) is obtained, which is equivalent to the equivalent control input Ueq (k): Become. Further, the reaching law input Urch (k) is calculated from the following equation (46). In Expression (46), F is a reaching law control gain.

Since the control output x (k) is specifically the upstream side exhaust pressure P3, the equivalent control input Ueq (k) and the reaching law input Urch (k) are calculated by the following equations (47) and (48). The P3CMD in Expression (47) is the target upstream exhaust pressure, and ΔP3 in Expression (48) is a control deviation (P3CMD−P3).

  Since the control input u (k) is specifically the turbine effective opening area Atb, it is converted into a duty ratio Duty of a control signal for driving the actuator of the variable vane 12, and the control signal of the duty ratio Duty is converted to the actuator. To be supplied.

  FIG. 3 is a block diagram illustrating a configuration of a supercharging pressure control module (including an exhaust gas recirculation amount control unit) that performs the above-described control. The function of each block is realized by calculation by the CPU of the ECU 20.

  The supercharging pressure control module shown in FIG. 3 includes a GACMD setting unit 31, a subtractor 32, an EGR controller 33, a P2CMD setting unit 41, a subtracting unit 42, a supercharging pressure controller 43, and a limiter 44. The exhaust pressure controller 45 is provided. The GACMD setting unit 31 sets the target intake air flow rate GACMD in accordance with the engine operating state, specifically, the basic fuel amount TI and the engine speed NE. The basic fuel amount TI is set so as to be substantially proportional to the required torque calculated according to the detected accelerator pedal operation amount AP. The subtracter 32 subtracts the detected intake air flow rate GA from the target intake air flow rate GACMD to calculate the intake air flow rate deviation ΔGA. The EGR controller 33 calculates an EGR valve lift amount command value LCMD so that the intake air flow rate deviation ΔGA becomes “0” by PID (proportional, integral, derivative) control. The ECU 20 controls the EGR valve 6 so that the lift amount LACT detected by the lift sensor 7 matches the lift amount command value LCMD.

  The P2CMD setting unit 41 sets a target boost pressure P2CMD according to the engine speed NE and the basic fuel amount TI. The target boost pressure P2CMD is set so as to increase as the engine speed NE increases and as the basic fuel amount TI increases. Therefore, at the time of acceleration at which the accelerator pedal is depressed, the target boost pressure P2CMD increases stepwise. The subtractor 42 subtracts the detected boost pressure P2 from the target boost pressure P2CMD to calculate a boost pressure deviation ΔP2. The supercharging pressure controller 43 calculates a target upstream side exhaust pressure P3CMD according to the supercharging pressure deviation ΔP2. More specifically, the target upstream side exhaust pressure P3CMD is calculated so that the supercharging pressure deviation ΔP2 becomes “0” by, for example, PID (proportional integral derivative) control. That is, the boost pressure controller 43 increases the target upstream exhaust pressure P3CMD when ΔP2> 0, and decreases the target upstream exhaust pressure P3CMD when ΔP2 <0.

The limiter 44 calculates an upstream limit value P3LMT by multiplying the detected downstream exhaust pressure P4 by a predetermined pressure ratio PR0. Here, the predetermined pressure ratio PR0 corresponds to the pressure ratio P3 / P4 when the flow velocity of the exhaust gas passing through the turbine 11 is the speed of sound, and is theoretically calculated by the following equation (50). In the equation (50), κ is the specific heat ratio of the exhaust gas.

  When the target upstream exhaust pressure P3CMD is equal to or lower than the upstream limit value P3LMT, the limiter 44 sets the target upstream exhaust pressure P3CMD as it is as the final target upstream exhaust pressure P3CMDF, while the target upstream exhaust pressure P3CMD is upstream. When the side limit value P3LMT is exceeded, the upstream limit value P3LMT is set as the final target upstream exhaust pressure P3CMDF.

  When the pressure ratio P3 / P4 increases, the mass flow rate of the exhaust gas that drives the turbine wheel 10 (hereinafter simply referred to as “turbine passage exhaust gas flow rate”) increases, but exceeds the pressure ratio PR0 at which the exhaust gas flow velocity reaches the sonic speed. And almost no increase. Therefore, by setting the predetermined pressure ratio in the vicinity of the pressure ratio PR0, for example, when the engine is accelerated, the exhaust gas flow rate through the turbine is rapidly increased without excessively increasing the upstream exhaust pressure P4, and the boost pressure P2 is increased. Can be quickly increased.

  The exhaust pressure controller 45 calculates the duty ratio Duty of the control signal for controlling the opening degree of the variable vane 12 so that the detected upstream exhaust pressure P3 matches the final target upstream exhaust pressure P3CMDF. That is, the exhaust pressure controller 45 controls the vane opening degree VO by sliding mode control using model parameters identified in real time based on the above-described control target model.

FIG. 4 is a block diagram showing the configuration of the exhaust pressure controller 45. The exhaust pressure controller 45 includes a scheduler 51, an identifier 52, a sliding mode controller 53, and a converter 54.
The scheduler 51 uses the engine rotational speed NE, the boost pressure P2, upstream exhaust pressure P3, the downstream exhaust pressure P4, the intake air flow rate GA, the basic fuel amount TI, the coefficients k _e and k _i, equation (21) And (22), the standard model parameters b _base and c _base are calculated. The intake air flow rate m _c dot in Expression (22) corresponds to the intake air flow rate GA, and the fuel flow rate m _f dot is calculated according to the basic fuel amount TI. The supercharging pressure differential value P2dot is calculated according to the detected change amount (P2 (k) -P2 (k-1)) of the supercharging pressure P2.

The identifier 52 calculates model parameters b (k) and c (k) from the reference model parameters b _base and c _base . Specifically, the model parameter b (k) is set as the reference model parameter b _base , and the model parameter c (k) is calculated by the identification calculation using Expression (31) using the reference model parameter c _base. To do.

  The sliding mode controller 53 calculates a control deviation ΔP3 (= P3CMDF−P3) from the detected upstream exhaust pressure P3 and the final target exhaust pressure P3CMDF inputted from the limiter 44, and the equations (43), (47) and (47) 48), the control input u (k), specifically, the turbine effective opening area Atb is calculated.

  The converter 54 converts the turbine effective opening area Atb into a duty ratio Duty of a control signal that controls an actuator that drives the variable vane 12.

FIG. 5 is a flowchart of the supercharging pressure control process for realizing the functions of the functional blocks described above. This process is executed every predetermined time by the CPU of the ECU 20.
In step S10, the target boost pressure P2CMD is set according to the engine speed NE and the basic fuel amount TI. In step S11, the detected boost pressure P2 is subtracted from the target boost pressure P2CMD to calculate the boost pressure deviation ΔP2. In step S12, the target upstream exhaust pressure P3CMD is calculated using, for example, PID control so that the supercharging pressure deviation ΔP2 becomes “0”. In step S13, an upstream limit value P3LMT is calculated by multiplying the detected downstream exhaust pressure P4 by a predetermined pressure ratio PR0. Next, it is determined whether or not the target upstream exhaust pressure P3CMD calculated in step S12 is larger than the upstream limit value P3LMT (step S14).

  If P3CMD ≦ P3LMT in step S14, the final target upstream exhaust pressure P3CMDF is set to the target upstream exhaust pressure P3CMD (step S16). If P3CMD> P3LMT, the final target upstream exhaust pressure P3CMDF is set to the upstream limit value P3LMT (step S15). Through steps S13 to S16, the final target upstream exhaust pressure P3CMDF is set so that the pressure ratio PR does not exceed the predetermined pressure ratio PR0.

  In step S17, the exhaust pressure control process shown in FIG. 6 is executed to calculate the duty ratio Duty of the actuator control signal. In step S18, a control signal for the duty ratio Duty is output to the actuator.

FIG. 6 is a flowchart of the exhaust pressure control process executed in step S17 of FIG.
In step S21, various engine operation parameters supplied from the sensor are read. In step S22, reference model parameters b _base and c _base are calculated by the above equations (21) and (22). In step S23, the identification error eid is calculated from the equation (33).

  In step S24, the model parameter c (k) is identified using the identification error eid. In step S25, the turbine effective opening area Atb is calculated by sliding mode control. In step S26, the turbine effective opening area Atb is converted into a duty ratio Duty of the control signal. In step S27, a duty ratio Duty limit process is performed so that the duty ratio Duty falls within a predetermined upper and lower limit value range.

  FIG. 7 is a time chart showing the transition of main parameters in the above-described supercharging pressure control. FIG. 7 shows an operation example in which the target boost pressure P2CMD increases stepwise at time t1, and the lift amount command value LCMD of the EGR valve 6 increases stepwise at time t2.

  At time t1, the upstream side target exhaust pressure P3CMD increases corresponding to the increase in the target supercharging pressure P2CMD (FIGS. (A) and (b)). Then, the reaching law input Urch and the equivalent control input Ueq change rapidly, the vane opening VO, that is, the turbine effective opening area Atb increases ((d) in the figure), and the upstream exhaust pressure P3 becomes the upstream target exhaust. It changes following the atmospheric pressure P3CMD ((b) in the figure). As a result, the supercharging pressure P2 coincides with the target supercharging pressure P2CMD with a slight delay ((a) in the figure).

  At time t2, the upstream exhaust pressure P3 becomes smaller than the target upstream exhaust pressure P3CMD (FIG. (B)) corresponding to the increase in the exhaust gas recirculation amount (FIG. (D)), but the turbine effective opening area Atb. Increases rapidly ((d) in the figure), and the upstream exhaust pressure P3 is returned to the target upstream exhaust pressure P3CMD ((b) in the figure). As a result, fluctuations in the supercharging pressure P2 can be suppressed ((a) in the figure).

As described above, in the present embodiment, the detected upstream exhaust pressure P3 is the target exhaust pressure based on the control target model that models the control target from the intake pipe 2 of the engine 1 to the exhaust pipe 4 via the cylinder 1a. to match the P3CMD (P3CMDF), the opening degree VO of the variable vane 12 is controlled, the model parameters c that define the controlled object model, is a function of the exhaust gas recirculation amount m _r dot passing through an exhaust gas recirculation mechanism . Therefore, to identify the model parameter c which is a function of its exhaust gas recirculation amount in real time, by using the model parameter c that the identified, exhaust gas recirculation amount m _r dot exhaust pressure control and the supercharging pressure in consideration of the influence of Control is performed. Therefore, it is possible to perform supercharging pressure control with good responsiveness according to the exhaust gas recirculation amount with a relatively simple configuration.

  In the present embodiment, the variable vane 12 and the actuator that drives the variable vane 12 correspond to exhaust gas flow rate variable means, the upstream exhaust pressure sensor 25 corresponds to upstream exhaust pressure detection means, and the downstream exhaust pressure sensor 26 corresponds to The ECU 20 corresponds to the downstream exhaust pressure detection means, and the control means is constituted by the ECU 20. That is, the processing shown in FIG. 5 and FIG. 6 executed by the CPU of the ECU 20 corresponds to control means, and includes identification means, target boost pressure setting means, and target upstream side exhaust pressure setting means. Specifically, step S10 in FIG. 5 corresponds to the target boost pressure setting means, steps S11 and S12 correspond to the target upstream side exhaust pressure setting means, and steps S22 to S24 in FIG. 6 correspond to the identification means. .

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, only the model parameter c is sequentially identified according to the identification error eid, but the model parameter b may also be sequentially identified by the same method.

  Further, the downstream side exhaust pressure P4 may be calculated by detecting the atmospheric pressure PA with an atmospheric pressure sensor and adding the correction amount ΔP to the detected atmospheric pressure PA. Since the DPF is provided on the downstream side of the turbine 11 as in the present embodiment and the NOx absorption catalyst for purifying NOx is provided, the downstream exhaust pressure P4 is slightly higher than the atmospheric pressure PA. . Accordingly, a correction amount ΔP to be added to the atmospheric pressure PA is obtained in advance, and the downstream exhaust pressure P4 (approximate value) is simply obtained by adding the correction amount ΔP to the detected atmospheric pressure PA. Can do. In this case, the atmospheric pressure sensor and the ECU 20 constitute downstream exhaust pressure detection means. Thereby, it is not necessary to provide the downstream side exhaust pressure sensor 26, and the configuration can be simplified.

Further, in the above-described embodiment, the example in which the present invention is applied to the supercharging pressure control in the internal combustion engine including the turbocharger having the variable vane is shown. However, the present invention is a supercharging pressure control device having the following configuration. It is also applicable to.
(1) A turbocharger having a fixed capacity, a bypass passage that bypasses the turbine of the turbocharger, and a wastegate valve provided in the bypass passage, and by changing the opening of the wastegate valve, A control device configured to control a supercharging pressure by changing an exhaust amount flowing into a turbine. In this case, the bypass passage and the wastegate valve correspond to the exhaust gas flow rate varying means.
(2) A turbocharger having a fixed capacity is provided, and the supercharging pressure is controlled by changing the exhaust amount of the internal combustion engine according to the engine operating state (for example, the engine speed and the target fuel amount). Control unit. In this control device, the exhaust amount is changed by changing the amount of fuel supplied to the internal combustion engine or the amount of intake air, for example. In this case, the control unit for controlling the exhaust amount corresponds to the exhaust gas flow rate varying means.

In the above-described embodiment, an example is shown in which the present invention is applied to the supercharging pressure control of the diesel internal combustion engine of the present invention. However, the present invention is also applicable to supercharging pressure control of a gasoline internal combustion engine.
The present invention can also be applied to supercharging pressure control of a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a figure for demonstrating a control object model. It is a block diagram which shows the structure of a supercharging pressure control module. FIG. 4 is a block diagram showing a configuration of an exhaust pressure controller shown in FIG. 3. It is a flowchart of the process which performs supercharging pressure control. It is a flowchart of the exhaust pressure control process performed by the process of FIG. It is a time chart for demonstrating the example of control operation.

Explanation of symbols

1 Internal combustion engine 2 Intake pipe 5 Exhaust gas recirculation passage (exhaust gas recirculation mechanism)
6 Exhaust gas recirculation valve (exhaust gas recirculation mechanism)
8 Turbocharger 10 Turbine wheel 11 Turbine 12 Variable vane 15 Compressor wheel 16 Compressor 20 Electronic control unit (control means, identification means, target boost pressure setting means, target upstream side exhaust pressure setting means))
21 Intake air flow rate sensor 22 Supercharging pressure sensor 23 Intake air temperature sensor 24 Exhaust temperature sensor 25 Upstream exhaust pressure sensor (upstream exhaust pressure detection means)
26 Downstream exhaust pressure sensor (downstream exhaust pressure detection means)

Claims (4)

A turbocharger having a compressor wheel for pressurizing air sucked into the internal combustion engine, a turbine wheel connected to the compressor wheel and driven to rotate by the kinetic energy of the exhaust gas of the engine, and exhaust blown to the turbine wheel In a supercharging pressure control device for an internal combustion engine comprising an exhaust gas flow rate variable means for changing the flow rate of gas and an exhaust gas recirculation mechanism for recirculating exhaust gas to an intake system
Based on the operating state of the engine, a lift amount command value of the exhaust gas recirculation valve for controlling the exhaust gas recirculation amount passing through the exhaust gas recirculation mechanism is calculated, and the lift amount of the exhaust gas recirculation valve is calculated as the lift amount command value. An EGR controller that controls to match,
Upstream exhaust pressure detection means for detecting the exhaust pressure upstream of the turbine wheel;
Based on the control target model that models the control target from the intake system to the exhaust system of the engine, so that the upstream exhaust pressure detected by the upstream exhaust pressure detection means matches the target upstream exhaust pressure, Control means for controlling the exhaust gas flow rate variable means,
The controlled object model is defined using a first model parameter that is multiplied by an operation amount of the exhaust gas flow rate varying means that is a control input, and a second model parameter that indicates a disturbance applied to the controlled object,
The second model parameter, Ri functions der the exhaust gas recirculation amount that passes through the exhaust gas recirculation mechanism,
The supercharging pressure control apparatus for an internal combustion engine , wherein the control means includes identification means for identifying the first and second model parameters, and performs the control using the identified model parameters . The supercharging pressure control device for an internal combustion engine according to claim 1 , wherein the control means performs the control by sliding mode control using the identified model parameter. The apparatus further comprises a supercharging pressure detecting means for detecting a supercharging pressure, the control means comprising a target supercharging pressure setting means for setting a target supercharging pressure in accordance with an operating state of the engine, and a detected supercharging pressure. 3. A boost pressure control for an internal combustion engine according to claim 1, further comprising target upstream exhaust pressure setting means for setting the target upstream exhaust pressure so as to coincide with the target boost pressure. apparatus. The apparatus further comprises a downstream exhaust pressure detecting means for detecting an exhaust pressure downstream of the turbine wheel, and the control means prevents the pressure ratio of the upstream exhaust pressure to the downstream exhaust pressure from exceeding a predetermined pressure ratio. The supercharging pressure control device for an internal combustion engine according to any one of claims 1 to 3 , wherein the exhaust gas flow rate varying means is controlled.

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