JP5155911B2 - 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 including a turbocharger.

  2. Description of the Related Art Conventionally, a compressor wheel that pressurizes air sucked into an internal combustion engine, a turbine wheel that is connected to the compressor wheel and is driven to rotate when exhaust is blown, and a variable vane that changes the flow rate of the exhaust blown to the turbine wheel There is known a variable capacity turbocharger comprising: In such a turbocharger, the supercharging pressure can be adjusted to an appropriate pressure by controlling the opening of the variable vane.

  The variable vane is opened and closed by an actuator, and this actuator is controlled by a controller based on a predetermined program. However, if the turbocharger or variable vane actuators are uneven or deteriorated, there will be a gap between the controller opening for the variable vane and the actual opening of the variable vane. As a result, the control accuracy of the supercharging pressure may be reduced. Therefore, Patent Document 1 discloses a technique for correcting the influence of such object variation and deterioration.

  More specifically, Patent Document 1 discloses a control device that sets a reference opening of a variable vane when the engine is started. In this control device, every time the engine is started, the opening degree when the variable vane is fully closed is learned, and the reference opening degree is set based on the opening degree when the variable vane is fully closed. As a result, the reference opening can be set stably regardless of the variation and deterioration of the turbocharger and variable vane.

Japanese Patent No. 399944

  However, in the control device disclosed in Patent Document 1, the influence due to object variation and deterioration is corrected only on the closing side of the variable vane. That is, with this control device, it is not possible to appropriately correct the effects of object variations and deterioration over the entire opening of the variable vane. Also, such correction is made only when the engine is started.

  The present invention has been made in view of the above-described problems, and can correct the influence of object variations and deterioration over the entire opening of the exhaust flow variable mechanism, and also as described above even during engine operation. An object of the present invention is to provide a supercharging pressure control device capable of making a simple correction.

  In order to achieve the above object, an invention according to claim 1 is directed to a compressor wheel (82) for pressurizing air sucked into the internal combustion engine (1), and an exhaust gas connected to the compressor wheel and discharged from the internal combustion engine. A turbocharger (8) having a turbine wheel (81) that is rotationally driven by gas blowing, and an exhaust flow rate variable mechanism (84, 85) that changes the flow rate of exhaust gas blown to the turbine wheel by opening and closing operations. , And a supercharging pressure control device for an internal combustion engine that determines the opening of the exhaust flow variable mechanism so that the actual supercharging pressure (P2) matches a predetermined target supercharging pressure (P2CMD), Target values (PRCMD, P3CMD) for a predetermined control amount (PR, P3) are calculated so that the actual supercharging pressure (P2) matches the target supercharging pressure (P2CMD). Target value calculation means (41, 421), a control value and a predetermined physical quantity (T3, P3, G), and a model that associates the opening of the exhaust flow variable mechanism with the target value of the control amount. An opening degree instruction value calculating means (422) for calculating an opening degree instruction value (VO, WO) of the exhaust flow rate variable mechanism according to (PRCMD, P3CMD), and an actual value of the control amount (based on the model) PR, P3) calculates the estimated opening value (VOHAT, WOHAT) of the exhaust flow variable mechanism according to the exhaust flow rate variable mechanism, and the estimated opening value (VOHAT, WOHAT) matches the opening instruction value (VO, WO). As described above, the present invention is characterized by comprising correction parameter calculation means (426) for calculating correction parameters (a, b) for correcting the model of the opening degree instruction value calculation means.

  According to a second aspect of the present invention, in the supercharging pressure control device for an internal combustion engine according to the first aspect, the physical quantity includes an exhaust pressure (P3) upstream of the turbine wheel, and an exhaust pressure upstream of the turbine wheel. It includes a temperature (T3) and a mass flow rate (MT) of exhaust gas that drives the turbine wheel.

  According to a third aspect of the present invention, in the supercharging pressure control device for an internal combustion engine according to the first or second aspect, the correction parameter calculation means includes a correction parameter (NE, TRQ) according to an operating state (NE, TRQ) of the engine. The speed of updating a, b) is changed.

  According to a fourth aspect of the present invention, in the supercharging pressure control device for an internal combustion engine according to the first or second aspect, the correction parameter calculating means adjusts the correction parameter according to the opening degree (VO) of the exhaust flow rate variable mechanism. The speed at which (a, b) is updated is changed.

  According to a fifth aspect of the present invention, in the supercharging pressure control device for an internal combustion engine according to any one of the first to third aspects, the exhaust flow rate variable mechanism has an inlet area of the exhaust gas flowing into the turbine wheel by an opening / closing operation. The model includes a variable vane (84) for changing the control amount, and the model associates the control amount and the predetermined physical amount with the opening of the variable vane.

  A sixth aspect of the present invention is the supercharging pressure control device for an internal combustion engine according to any one of the first to third aspects, wherein the exhaust flow rate variable mechanism bypasses the upstream side and the downstream side of the turbine wheel. A wastegate valve (85) for opening and closing a bypass passage is included, and the model is characterized by associating the control amount and a predetermined physical quantity with an opening degree of the wastegate valve.

  According to the first aspect of the present invention, the target value calculation means calculates the target value for the predetermined control amount so that the actual boost pressure matches the target boost pressure. Further, the opening instruction value calculation means is based on a model that associates the control amount and the predetermined physical quantity with the opening of the exhaust flow variable mechanism, and the opening instruction value of the exhaust flow variable mechanism according to the target value. Is calculated. The opening degree of the exhaust flow rate variable mechanism is changed according to the opening degree instruction value.

  Here, the correction parameter calculation means calculates the opening estimated value of the exhaust flow variable mechanism according to the measured value of the control amount based on the model of the opening instruction value calculation means, and further, this opening estimation A correction parameter for correcting the model of the opening instruction value calculating means is calculated so that the value matches the above-described opening instruction value. In other words, if an error occurs between the opening command value and the estimated opening value due to variations or deterioration of the turbocharger or exhaust flow variable mechanism, there is a correction parameter that modifies the model to eliminate this error. Calculated. As described above, by correcting the model that associates the control amount and the predetermined physical quantity with the opening degree of the exhaust flow variable mechanism, it is possible to correct the influence of object variations and deterioration over the entire opening degree of the exhaust flow variable mechanism. it can. Further, such correction can be performed even while the engine is operating.

  By the way, conventionally, when feedback control of the supercharging pressure is performed, the feedback gain is set to be low in consideration of deterioration of the turbocharger and the exhaust flow variable mechanism. According to this configuration, the model is modified according to the deterioration of the turbocharger and the exhaust flow rate variable mechanism, so that the feedback gain can be set higher than in the conventional case. For this reason, controllability can be improved.

  According to the second aspect of the present invention, the model changes depending on the engine operating conditions such as the exhaust pressure upstream of the turbine wheel, the exhaust temperature upstream of the turbine wheel, and the mass flow rate of the exhaust driving the turbine wheel. The physical quantity is associated with the opening of the exhaust flow variable mechanism. By correcting such a model as described above, it is possible to accurately correct the opening of the exhaust flow variable mechanism even under any operating conditions.

According to the invention described in claim 3, the correction parameter calculation means changes the update speed of the correction parameter for correcting the model in accordance with the operating state of the internal combustion engine. By the way, when determining the opening degree of the exhaust flow variable mechanism based on this model, it is necessary to detect or estimate a physical quantity referred to in the model. However, depending on the operation state of the internal combustion engine, there is a large error in the detected value or estimated value of the physical quantity. In such an operating state, the model correction may become unstable. According to the present invention, for example, in an operating state in which the detected value of the physical quantity and the error in the estimated value are large, the update speed of the correction parameter is slowed. The update speed of the correction parameter can be increased. As a result, a stable model can be corrected.
Moreover, although the above-mentioned model associates a predetermined physical quantity with the opening of the exhaust flow variable mechanism, there is a combination of a physical quantity and an opening with a low appearance frequency depending on the operating state. According to the present invention, for example, in such an operation state, the correction accuracy of the model can be improved by increasing the update speed compared to other operation states.

  According to the fourth aspect of the present invention, the correction parameter calculation means changes the update speed of the correction parameter for correcting the model according to the opening degree of the exhaust flow rate variable mechanism. By the way, the opening degree of the exhaust flow variable mechanism generally has a non-linear characteristic. Specifically, the turbine flow rate or the exhaust pressure change amount with respect to the opening change amount is large on the throttle side of the opening, and the turbine flow rate or exhaust pressure change amount with respect to the opening change amount is small on the opening side. In contrast to a model that determines the opening degree of the exhaust flow rate variable mechanism having such nonlinear characteristics, the correction accuracy of the model can be improved by changing the update speed of the correction parameter according to the opening degree as described above. it can.

It is a figure which shows the structure of the internal combustion engine which concerns on 1st Embodiment of this invention, and its supercharging pressure control apparatus. It is a block diagram which shows the structure of the module for performing the supercharging pressure control which concerns on the said embodiment. It is a figure which shows the specific example of the model which concerns on the said embodiment. It is a figure which shows the correlation with the instruction | indication vane opening degree which concerns on the said embodiment, and an actual vane opening degree. It is a figure which shows the map for determining the forgetting factor which concerns on the said embodiment according to the driving | running state of an engine. It is a figure which shows the map for determining the forgetting factor which concerns on the said embodiment according to a vane opening degree. It is a figure which shows the result of the simulation of the supercharging pressure control which concerns on the said embodiment. It is a block diagram which shows the structure of the module for performing the supercharging pressure control which concerns on 2nd Embodiment of this invention.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a supercharging pressure control device thereof according to the present embodiment. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a combustion chamber of a cylinder 7, and the cylinder 7 is provided with a fuel injection valve (not shown). These fuel injection valves are electrically connected by an electronic control unit (hereinafter referred to as “ECU”) 40, and the valve opening time and valve closing time of the fuel injection valve are controlled by the ECU 40.

  The engine 1 includes an intake pipe 2 through which intake air circulates, an exhaust pipe 4 through which exhaust gas circulates, an exhaust gas recirculation passage 6 that recirculates part of the exhaust gas in the exhaust pipe 4 to the intake pipe 2, and intake air into the intake pipe 2. And a turbocharger 8 for pressure-feeding.

  The intake pipe 2 is connected to an intake port of each cylinder 7 of the engine 1 through a plurality of branch portions of the intake manifold. The exhaust pipe 4 is connected to an exhaust port of each cylinder 7 of the engine 1 through a plurality of branch portions of the exhaust manifold. The exhaust gas recirculation passage 6 branches from the exhaust pipe 4 and reaches the intake pipe 2.

  The turbocharger 8 includes a turbine wheel 81 provided in the exhaust pipe 4, a compressor wheel 82 provided in the intake pipe 2, and a turbine shaft 83 that connects the turbine wheel 81 and the compressor wheel 82. The turbine wheel 81 is rotationally driven by blowing exhaust discharged from the engine 1. The compressor wheel 82 is rotationally driven by the turbine wheel 81 to pressurize the intake air of the engine 1 and pump it into the intake pipe 2.

  In addition, the turbocharger 8 includes a variable vane 84 and a wastegate valve 85 as an exhaust flow rate variable mechanism that changes the flow rate of the exhaust blown to the turbine wheel 81. The variable vane 84 changes the inlet area of the exhaust gas flowing into the turbine wheel 81 by the opening / closing operation thereof, thereby changing the flow rate of the exhaust gas blown to the turbine wheel 81 and changing the rotational speed of the turbine wheel 81. . The variable vane 84 is connected to the ECU 40 via an actuator (not shown), and the opening degree is controlled by the ECU 40.

  The wastegate valve 85 is provided in a bypass passage 86 that bypasses the upstream side and the downstream side of the turbine wheel 81 in the exhaust pipe 4, and opens and closes the bypass passage 86. That is, by opening and closing the waste gate valve 85 and discharging a part of the exhaust gas without passing through the turbine wheel 81, the flow rate of the exhaust gas blown to the turbine wheel 81 can be changed. The waste gate valve 85 is connected to the ECU 40 via an actuator (not shown), and the opening degree is controlled by the ECU 40.

  An intercooler 5 that cools the air pressurized by the turbocharger 8 and a throttle valve 9 that controls the intake air amount of the engine 1 are provided on the downstream side of the turbocharger 8 in the intake pipe 2. . The throttle valve 9 is connected to the ECU 40 via an actuator (not shown), and the opening degree is controlled by the ECU 40.

  A diesel particulate filter 15 that collects particulate matter contained in the exhaust gas is provided in the exhaust pipe 4 on the downstream side of the turbocharger 8.

  The exhaust gas recirculation passage 6 connects the exhaust pipe 4 and the intake manifold of the intake pipe 2 to recirculate part of the exhaust discharged from the engine 1. The exhaust gas recirculation passage 6 is provided with an EGR valve 13 that controls the flow rate of the exhaust gas that is recirculated. The EGR valve 13 is connected to the ECU 40 via an actuator (not shown), and the valve opening degree is controlled by the ECU 40.

  The ECU 40 includes a supercharging pressure sensor 21 that detects an intake pressure downstream of the compressor wheel 82 in the intake pipe 2, that is, a supercharging pressure P <b> 2, and an exhaust pressure (hereinafter, “ The upstream exhaust pressure sensor 22 that detects P3) and the downstream exhaust that detects the exhaust pressure downstream of the turbine wheel 81 in the exhaust pipe 4 (hereinafter referred to as "downstream exhaust pressure") P4. The upstream side exhaust temperature sensor 24 that detects the exhaust temperature upstream of the turbine wheel 81 (hereinafter referred to as “upstream side exhaust temperature”) T3 of the pressure sensor 23 and the exhaust pipe 4, and the rotation angle of the crankshaft of the engine 1 is detected. A crank angle position sensor 25 for detecting the amount of depression of the accelerator pedal of the vehicle driven by the engine 1 and an accelerator pedal sensor 26 for detecting the depression amount AP. The detection signals of these sensors are supplied to the ECU 40. Further, the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 1 is calculated by the ECU 40 based on the output of the crank angle position sensor 25.

  The ECU 40 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter, “ CPU ”). In addition, the ECU 40 includes a storage circuit for storing various calculation programs executed by the CPU and calculation results, a variable vane 84 and a wastegate valve 85 of the turbocharger 8, a throttle valve 9, an EGR valve 13, and an engine 1. And an output circuit that outputs a control signal to each actuator that drives the fuel injection valve.

Next, the supercharging pressure control for controlling the vane opening degree of the variable vane 84 will be described with reference to FIGS.
FIG. 2 is a block diagram showing a configuration of a module for executing supercharging pressure control. The function of this module is realized by the ECU 40 having the hardware configuration as described above.

  The module shown in FIG. 2 includes two feedback controllers, a target upstream side exhaust pressure calculation unit 41 and a vane opening degree control unit 42, and the actual boost pressure P2 matches a target boost pressure P2CMD described later. Thus, the instruction value of the vane opening (hereinafter simply referred to as “vane opening”) VO is determined. More specifically, these target upstream side exhaust pressure calculation unit 41 and vane opening degree control unit 42 provide two control outputs (actual boost pressure P2 and actual upstream exhaust pressure P3 or actual front / rear exhaust pressure ratio PR ( = P3 / P4)), the vane opening VO is determined by so-called cascade control.

The target upstream side exhaust pressure calculation unit 41 includes a supercharging pressure controller 412, a target value limiter 414, and a target value filter 416.
The supercharging pressure controller 412 calculates a target value (hereinafter referred to as “target upstream exhaust pressure”) P3CMD of the upstream exhaust pressure so that the actual supercharging pressure P2 matches a target supercharging pressure P2CMD described later. . Specifically, the deviation E between the actual boost pressure P2 and the target boost pressure P2CMD is defined by the following equation (1), and the sliding mode control described later is performed so that the deviation E (k) converges to 0. Based on this, a control input U (controller output) is calculated, and the calculated control input U is converted into a target upstream side exhaust pressure P3CMD.

  Here, the symbol (k) is a symbol indicating the discretized time, and indicates that the data is detected or calculated every predetermined control period. That is, when the symbol (k) is data detected or calculated at the current control timing, the symbol (k-1) indicates data detected or calculated at the previous control timing. In the following description, the symbol (k) is omitted as appropriate.

Next, a sliding mode control algorithm represented by the following formulas (2) to (5) will be described. Sliding mode control is a development of so-called response command type control that can specify the convergence speed of the controlled variable.The tracking speed with respect to the target value of the controlled variable and the convergent speed of the controlled variable when a disturbance is applied. This control can be specified individually.

As shown in the above equation (2), the control input U (k) includes the reaching law input U _RCH (k) shown in the above equation (3) and the adaptive law input U _ADP (k) shown in the above equation (4). It is calculated by the sum of.
The reaching law input U _RCH (k) is an input for placing the deviation E (k) on a switching straight line described later, and a predetermined reaching law control gain K is added to the switching function σ (k) shown in the above equation (5). Calculated by multiplying by _RCH .
The adaptive law input U _ADP (k) is an input for suppressing the influence of modeling errors and disturbances, and placing the deviation E (k) on a switching straight line, which will be described later, and has a predetermined integral value of the switching function σ (k). _Is calculated by multiplying the adaptive law control gain K _ADP .

  As shown in the above equation (5), the switching function σ (k) is multiplied by a predetermined switching function setting parameter VPOLE to the deviation E (k) at the current control and the deviation E (k−1) at the previous control. It is calculated by the sum of

Here, the relationship between the switching function setting parameter VPOLE and the convergence speed of the deviation E (k) will be described.
As shown in the above equation (5), in the phase plane in which the horizontal axis is the deviation E (k−1) at the previous control and the vertical axis is the deviation E (k) at the current control, the switching function σ ( k) A combination of deviations E (k) and E (k−1) satisfying 0 is a straight line having a slope of −VPOLE. In particular, this straight line is called a switching straight line. On this switching line, by setting −VPOLE to a value smaller than 1 and larger than 0, E (k−1)> E (k) is satisfied, so that the deviation E (k) converges to 0. It becomes. The sliding mode control is a control that pays attention to the behavior of the deviation E (k) on the switching straight line.
That is, by performing control so that the combination of the deviation E (k) at the current control time and the deviation E (k−1) at the previous control time is on this switching straight line, disturbances and modeling errors can be prevented. Robust control can be realized, and the control amount can be converged without excessive overshoot with respect to the target value.

  The target boost pressure P2CMD is appropriately set by the target boost pressure setting unit 43 according to the operating state of the engine 1. Specifically, the target supercharging pressure P2CMD calculates a basic fuel amount TI (specifically, a valve opening time of the fuel injection valve) according to the required torque TRQ calculated according to the depression amount AP. It is set according to the basic fuel amount TI and the engine speed NE. The target boost pressure P2CMD is set so as to increase as the basic fuel amount TI increases and as the engine speed NE increases. Therefore, at the time of acceleration at which the accelerator pedal is depressed, the target boost pressure P2CMD increases stepwise.

  The target value limiter 414 performs limit processing with the predetermined limit value P3LMT as an upper limit value for the target upstream side exhaust pressure P3CMD. That is, when the calculated target upstream exhaust pressure P3CMD is larger than the predetermined limit value P3LMT, this limit value P3LMT is set as the target upstream exhaust pressure.

The target value filter 416 calculates a target upstream exhaust pressure that can actually be achieved by performing the following filter processing on the target upstream exhaust pressure P3CMD subjected to the limit processing. Specifically, the filter value P3CMDF of the target upstream side exhaust pressure P3CMD is calculated by a first-order lag filter algorithm expressed by the following equation (6). In the following formula (6), R is a target value filter coefficient, and is set between −1 and 0. In the following description, the filter value P3CMDF of the target upstream exhaust pressure P3CMD is simply referred to as target upstream exhaust pressure unless there is a possibility of confusion.

  The vane opening degree control unit 42 includes an exhaust pressure controller 421, a vane opening degree determination unit 422, and a correction parameter calculation unit 426. The actual upstream exhaust pressure P3 is changed to the target upstream exhaust pressure P3CMD. The vane opening VO is determined so as to match.

  The exhaust pressure controller 421 performs exhaust before and after actual exhaust so that the actual upstream exhaust pressure P3 matches the target upstream exhaust pressure P3CMDF, that is, the actual boost pressure P2 matches the target boost pressure P2CMD. A target value PRCMD of the pressure ratio PR (hereinafter referred to as “target front / rear exhaust pressure ratio”) is calculated.

Specifically, the exhaust pressure controller 421 defines a deviation E (k) between the actual upstream exhaust pressure P3 and the target upstream exhaust pressure P3CMDF by the following equation (7), and the deviation E (k) is 0. The control input U is calculated based on the sliding mode control shown in the above formulas (2) to (5) so as to converge to the above, and the calculated control input U is converted into the target front-rear exhaust pressure ratio PRCMD.

  The vane opening degree determination unit 422 calculates a vane opening degree VO corresponding to the target front-rear exhaust pressure ratio PRCMD calculated by the exhaust pressure controller 421 based on a turbine model described later. More specifically, the vane opening degree determination unit 422 calculates a reference value (hereinafter referred to as “reference vane opening degree”) VOBS of the vane opening degree by the reference opening degree determination unit 423, and uses the reference vane opening degree VOBS as the reference vane opening degree VOBS. The reference opening is corrected by the reference opening correction unit 424, and the corrected opening is determined as the vane opening VO.

  The reference opening degree determination unit 423 calculates a reference vane opening degree VOBS based on a turbine model that describes the dynamic characteristics of the turbine wheel 81 of the turbocharger 8 as described below.

  FIG. 3 is a diagram showing the flow characteristics at each vane opening in the reference state of the turbocharger and the variable vane, and is a diagram showing a specific example of the turbine model referred to by the reference opening determining unit. In FIG. 3, the horizontal axis represents the front / rear exhaust pressure ratio PR, and the vertical axis represents the corrected flow rate G. The flow rate characteristic indicates a relationship between the front / rear exhaust pressure ratio PR and the corrected flow G in a state where the vane opening degree is kept constant. FIG. 3 shows only the flow characteristics when the vane opening is 20%, 40%, 60%, 80%, and 100%. In the present embodiment, the new state of the turbocharger and the variable vane is used as a reference state.

  The corrected flow rate G is the mass flow rate of the exhaust gas that drives the turbine wheel, that is, the mass flow rate of the exhaust gas that has passed through the turbine wheel (hereinafter referred to as “turbine flow rate”) MT, and the upstream exhaust temperature T3 and the upstream exhaust pressure P3. The original corrected flow rate is shown. The corrected flow rate G is calculated according to the turbine passage flow rate MT, the upstream side exhaust temperature T3, and the upstream side exhaust pressure P3 based on a predetermined definition formula.

As shown in FIG. 3, in a state where the vane opening degree is kept constant, the corrected flow rate G increases as the front / rear exhaust pressure ratio PR increases. Further, at any vane opening, the corrected flow rate G becomes substantially constant when the front-rear exhaust pressure ratio becomes larger than a predetermined value.
Further, as shown in FIG. 3, the interval between the flow rate characteristic curves at each vane opening becomes narrower as the vane opening becomes larger (as the variable vane becomes the opening side). This indicates that changes in the supercharging pressure and the upstream exhaust pressure with respect to the operation on the opening side of the variable vane are smaller than changes in the supercharging pressure and the upstream exhaust pressure with respect to the operation on the throttle side. That is, the vane opening has a non-linear characteristic with respect to the supercharging pressure or the upstream exhaust pressure.

  Returning to FIG. 2, the reference opening degree determination unit 423 performs the target front / rear exhaust pressure ratio based on the turbine model as described above in which the front / rear exhaust pressure ratio PR and the corrected flow rate G are associated with the opening of the variable vane. A vane opening degree corresponding to the PRCMD and the corrected flow rate G is calculated, and this is set as a reference vane opening degree VOBS.

  The reference opening degree correction unit 424 corrects the reference vane opening degree VOBS based on the correction parameter determined by the correction parameter identifier 428 described later, and determines this as the vane opening degree VO.

  FIG. 4 is a diagram illustrating a correlation between the instruction vane opening and the actual vane opening. In the system including the turbocharger and the variable vane in the above-described reference state, the actual vane opening and the instruction vane opening are substantially equal as shown in FIG. In this case, the dynamic characteristics of the actual turbocharger and variable vane are reproduced by the above-described model, that is, there is no error due to modeling, and therefore it is not necessary to correct the above-described reference vane opening VOBS.

  In contrast to systems with ideal initial characteristics of actual vane opening, in systems with turbochargers and variable vanes with variations, and systems with deteriorated turbochargers and variable vanes, the actual vane opening and The correlation between the indicated vane opening changes. That is, a deviation occurs between the instruction vane opening and the actual vane opening. In this case, the dynamic characteristics of the actual turbocharger and variable vane are not reproduced by the above-described model, that is, an error due to modeling occurs, so that the above-described reference vane opening VOBS needs to be corrected.

  In the present embodiment, an error model that reproduces changes in the characteristics of the actual vane opening caused by such object variations and deterioration is set, and the reference vane opening VOBS is corrected based on this error model.

  The broken line in FIG. 4 shows an example of the error model. As shown in FIG. 4, this error model is a reproduction of a change in the characteristics of the actual vane opening degree caused by the object variation and deterioration by a linear function. According to such an error model, for example, it is possible to reproduce a state where the variable vane is not fully squeezed. In addition to such a linear function, various functions can be considered as the error model.

Returning to FIG. 2, the reference opening degree correction unit 424 corrects the reference vane opening degree VOBS based on the error model set by the linear function as described above. More specifically, the reference vane opening VOBS is corrected based on the following formula (8), and this is determined as the vane opening VO. As the correction parameters a (k) and b (k), those identified by a correction parameter identifier 428 described later are used.

  The vane opening degree VO determined as described above is converted into a control signal having a duty ratio Duty corresponding to the opening degree by a converter (not shown) and then supplied to an actuator for driving the variable vane.

  The correction parameter calculation unit 426 includes a vane opening degree estimation unit 427 and a correction parameter identifier 428, and calculates the correction parameters a and b described above.

  The vane opening degree estimation unit 427 calculates the vane opening degree according to the actual front / rear exhaust pressure ratio PR and the corrected flow rate G based on the turbine model described above, and sets this as the estimated vane opening degree VOHAT.

  The correction parameter identifier 428 identifies the correction parameters a and b based on the estimated vane opening VOHAT and the reference vane opening VOBS so that the estimated vane opening VOHAT and the vane opening VO coincide with each other.

  Specifically, the correction parameters a and b are sequentially identified by the following sequential least square algorithm. In this sequential least square algorithm, the latest values a (k) and b (k) of the correction parameters are the latest values of the previous values a (k−1) and b (k−1) of the correction parameters and the estimated vane opening. It is calculated based on the value VOHAT (k) and the latest value VOBS (k) of the reference vane opening.

First, a vector θ (k) whose components are correction parameters a (k) and b (k) and a vector ζ (k) whose components are a reference vane opening VOBS (k) and “1” are expressed by the following formula ( It is defined in 9).
Also, an identification value VOHAT_HAT (k) is defined by the product of these vectors θ (k) and ζ (k) as shown in the following equation (10).

Next, as shown in the following equation (11), an identification error E (k) is defined by a deviation between the estimated vane opening VOHAT (k) and the identification value VOHAT_HAT (k).

In the successive least squares algorithm, the identification error E (k) is minimized, that is, the estimated vane opening VOHAT (k) and the vane opening VO (k) determined by the above equation (8). Based on the following formulas (12) to (14), the correction parameters a and b are determined so as to match.

Here, in the above formula (14), “I” is a unit matrix. Further, λ ₁ and λ ₂ are weight parameters, and the identification algorithm is classified into the following five algorithms by setting these parameters.
λ ₁ = 1, λ ₂ = 1 least square algorithm λ ₁ = λ (0 <λ ≦ 1), λ ₂ = 1 weighted least square algorithm λ ₁ = 1, λ ₂ = 0 fixed gain algorithm λ ₁ = 1, λ ₂ = λ (0 <λ <2) Asymptotic gain algorithm λ ₁ / λ ₂ = σ (fixed value) Fixed trace algorithm

In the above equation (12), the matrix M (k) multiplied by the vector θ (k−1) is a forgetting coefficient matrix. The forgetting coefficient matrix M (k) is a diagonal matrix with the diagonal components as the forgetting coefficients ρ ₁ and ρ ₂ as shown in the following equation (15).

By multiplying the forgetting coefficient matrix M (k) by the previous vector θ (k−1), for example, in the latest vector θ (k), the vector θ ( k−m) is suppressed by the power of ρ to the mth power. Therefore, these forgetting factors ρ ₁ and ρ ₂ have the effect of forgetting data up to the previous control and updating it with new data.

By making the forgetting factors ρ ₁ and ρ ₂ close to “1”, it is possible to make it difficult to forget data until the previous control. That is, by making the forgetting factors ρ ₁ and ρ ₂ close to “1”, the update rate of the data θ (k) can be made relatively slow.
Further, by making the forgetting factors ρ ₁ and ρ ₂ smaller from “1”, the data up to the previous control can be easily forgotten. That is, by reducing the forgetting factors ρ ₁ and ρ ₂ from “1”, the update rate of the data θ (k) can be made relatively fast.

In the present embodiment, the forgetting factors ρ ₁ and ρ ₂ are changed according to the operating state of the engine or the vane opening.

5 and 6 are diagrams showing examples of maps for determining the forgetting factors ρ ₁ and ρ ₂ . More specifically, FIG. 5 is a diagram showing a map for determining the forgetting factors ρ ₁ and ρ ₂ according to the engine operating state (required torque TRQ and engine speed), and FIG. It is a figure which shows the map for determining forgetting factor (rho) ₁ , (rho) ₂ according to opening degree (VO).

As shown in FIG. 5, when the forgetting factors ρ ₁ and ρ ₂ are changed in accordance with the operating state of the engine, the forgetting factors ρ ₁ and ρ ₂ are set to relatively small values in a high rotation and high load region. Increase the update speed of the correction parameters. In the region of low rotation and low load, the forgetting factors ρ ₁ and ρ ₂ are set to relatively large values, and the update speed of the correction parameter is made slower.

As shown in FIG. 6, when changing the forgetting factors ρ ₁ and ρ ₂ according to the vane opening, the forgetting factors ρ ₁ and ρ ₂ are set to relatively small values on the opening side of the vane opening. Increase the update speed of the correction parameters. In addition, on the throttle side of the vane opening, the forgetting factors ρ ₁ and ρ ₂ are set to relatively large values, and the update speed of the correction parameter is made slower.

  As shown in the equations (12) to (14), the recursive least square algorithm does not require an inverse matrix operation, and identifies the latest values a (k) and b (k) of the correction parameters. What is required is the previous values a (k−1) and b (k−1) of the correction parameters, the latest value VOHAT (k) of the estimated vane opening, and the latest value VOBS (k) of the reference vane opening. Only. This is a point that is greatly different from a normal least squares algorithm that requires computation of an inverse matrix and requires past values of parameters. Therefore, by identifying the correction parameters a and b by the above-described sequential least square algorithm, the burden on the calculation can be greatly reduced as compared with the case of identifying by the ordinary least square algorithm. it can. For this reason, it can be said that this is a statistical processing calculation suitable for an in-vehicle computer having a relatively small memory.

  Next, with reference to FIG. 7, the result of the supercharging pressure control simulation by the supercharging pressure control device of the present embodiment will be described.

FIG. 7 is a diagram illustrating a result of simulation of supercharging pressure control.
FIG. 7 shows a simulation result of the supercharging pressure and the vane opening when the object variation occurs with respect to the reference state. More specifically, the simulation result when the turbine model is corrected with the correction parameters as in the present embodiment is indicated by a solid line, and the simulation result when the turbine model is not corrected in the reference state is indicated by a broken line.

  As shown in FIG. 7, when the turbocharger and the variable vane are in the reference state with respect to the target supercharging pressure that changes stepwise, the actual supercharging pressure quickly follows the target supercharging pressure.

  On the other hand, when an object variation is given, a deviation occurs between the indicated opening and the actual opening. That is, a situation occurs in which the aperture cannot be fully throttled. Here, the case where the turbine model is corrected as in the present embodiment is compared with the case where the turbine model is not corrected.

If the turbine model is not modified, the relationship between the front / rear exhaust pressure ratio and the supercharging pressure is deviated from the reference state, so that there is a delay in following the actual supercharging pressure with respect to the target supercharging pressure as shown in FIG. Occurs and consequently vibrates.
On the other hand, when the turbine model is corrected, the followability of the actual boost pressure with respect to the target boost pressure can be stabilized by appropriately correcting the relationship between the front / rear exhaust pressure ratio and the boost pressure. Therefore, the vibration of the actual supercharging pressure as described above does not occur.

  As described above in detail, according to the present embodiment, the target upstream side exhaust pressure calculation unit 41 and the exhaust pressure controller 421 allow the target front-rear exhaust pressure so that the actual boost pressure P2 matches the target boost pressure P2CMD. The pressure ratio PRCMD is calculated. Moreover, the vane opening degree determination part 422 calculates the vane opening degree VO according to the target front-rear exhaust pressure ratio PRCMD based on the turbine model. The opening degree of the variable vane is changed according to the vane opening degree VO.

  Here, the correction parameter calculation unit 426 calculates an estimated vane opening VOHAT corresponding to the actual front / rear exhaust pressure ratio PR based on the turbine model of the vane opening determination unit 422, and further calculates the estimated vane opening VOHAT. The correction parameters a and b for correcting the output of the turbine model of the vane opening determining unit 422 are calculated so that the above-described vane opening VO coincides. That is, when an error occurs between the vane opening VO and the estimated vane opening VOHAT due to the variation or deterioration of the turbocharger or variable vane, the correction parameters a, b is calculated. As described above, by correcting the output of the turbine model that correlates the front / rear exhaust pressure ratio, the corrected flow rate, and the opening degree of the variable vane, it is possible to correct the influence of object dispersion and deterioration over the entire opening degree of the variable vane. it can. Further, such correction can be performed even while the engine is operating.

  By the way, conventionally, when feedback control of the supercharging pressure is performed, the feedback gain is set to be low in consideration of deterioration of the turbocharger and the variable vane. According to the present embodiment, the turbine model is corrected according to the deterioration of the turbocharger and the variable vane, so that the feedback gain can be set higher than in the conventional case. For this reason, controllability can be improved.

  Further, according to the present embodiment, the turbine model associates the physical quantity that changes depending on the engine operating condition such as the upstream exhaust pressure, the upstream exhaust temperature, and the turbine passage flow rate with the opening of the variable vane. By correcting the output of such a turbine model as described above, the opening degree of the variable vane can be accurately corrected even under any operating conditions.

Further, according to the present embodiment, the correction parameter calculation unit 426 changes the update speed of the correction parameters a and b for correcting the model according to the operating state of the engine. More specifically, in the low-rotation and low-load operating state in which the actual upstream exhaust pressure P3 and the actual front / rear exhaust pressure ratio PR are large, the update speed of the correction parameters a and b is slowed down to increase the actual upstream exhaust pressure. In the high rotation and high load operation state in which the error of P3 and the actual front / rear exhaust pressure ratio PR is small, the update speed of the correction parameters a and b is increased. As a result, a stable model can be corrected.
In addition, the above-described high-rotation and high-load operation state has a lower appearance frequency than other operation states. The correction accuracy of the model can be improved by increasing the update speed of the correction parameters a and b in such an operating state.

  Further, according to the present embodiment, the correction parameter calculation unit 426 changes the update speed of the correction parameters a and b for correcting the model according to the opening degree of the variable vane. As described above, with respect to a model that determines the opening degree of a variable vane having non-linear characteristics, the correction accuracy of the model can be improved by changing the update speed of the correction parameters a and b in accordance with the opening degree of the variable vane. Can be improved.

  In the present embodiment, the ECU 40 constitutes target value calculation means, opening instruction value calculation means, and correction parameter calculation means. More specifically, for example, the target upstream side exhaust pressure calculation unit 41 and the exhaust pressure controller 421 constitute target value calculation means, the vane opening degree determination unit 422 constitutes opening degree instruction value calculation means, and the correction parameter The calculation unit 426 constitutes a correction parameter calculation unit.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the first embodiment described above, the flow rate of the exhaust gas blown to the turbine wheel 81 is changed by changing the opening degree VO of the variable vane 84. On the other hand, in the present embodiment, the flow rate of the exhaust gas blown to the turbine wheel 81 is changed by changing the opening degree WO of the waste gate valve 85 and changing the flow rate of the exhaust gas flowing through the bypass passage 86.

  FIG. 8 is a block diagram showing a configuration of a module for executing supercharging pressure control. The function of this module is realized by processing executed by the ECU 40A.

  The wastegate valve opening degree control unit 42A includes an exhaust pressure controller 421 and a wastegate valve opening degree determination unit 422A so that the actual upstream exhaust pressure P3 matches the target upstream exhaust pressure P3CMD. In addition, the waste gate valve opening WO is controlled.

  The wastegate valve opening degree determination unit 47A determines a wastegate valve opening degree WO corresponding to the target front-rear exhaust pressure ratio PRCMD calculated by the exhaust pressure controller 46 based on a predetermined turbine model.

The valve opening degree determination unit 422A calculates the valve opening degree WO according to the target front / rear exhaust pressure ratio PRCMD calculated by the exhaust pressure controller 421 based on a model described later. More specifically, the valve opening determining unit 422A calculates a valve opening reference value (hereinafter referred to as “opening reference value”) WOBS by the reference opening determining unit 423A, and uses this opening reference value WOBS. The reference opening degree correction unit 424 corrects the corrected opening degree as the valve opening degree WO.
Here, in the turbine model referred to by the reference opening determination unit 423A, the relationship between the front / rear exhaust pressure ratio PR and the corrected flow rate G for each waste gate valve opening WO is similar to the turbine model shown in FIG. Is specified.

  The reference opening correction unit 424 corrects the reference vane opening WOBS based on the correction parameter determined by the correction parameter identifier 428 described later, and this is referred to as a valve opening instruction value (hereinafter simply referred to as “valve opening”). ) Determine as WO.

  The correction parameter calculation unit 426A includes a valve opening degree estimation unit 427A and a correction parameter identifier 428, and calculates the correction parameters a and b described above.

  The valve opening degree estimation unit 427A calculates the valve opening degree according to the actual front / rear exhaust pressure ratio PR and the corrected flow rate G based on the above-described turbine model, and sets this as the estimated valve opening degree WOHAT.

  The correction parameter identifier 428 uses a sequential least squares algorithm to correct the correction parameter a based on the estimated valve opening WOHAT and the reference valve opening WOBS so that the estimated vane opening WOHAT matches the valve opening WO. , B are identified.

  As described above in detail, according to the present embodiment, the same effects as those of the first embodiment can be obtained.

  In the present embodiment, the ECU 40A constitutes a target value calculation means, an opening instruction value calculation means, and a correction parameter calculation means. More specifically, for example, the target upstream side exhaust pressure calculation unit 41 and the exhaust pressure controller 421 constitute a target value calculation unit, the valve opening degree determination unit 422A constitutes an opening degree instruction value calculation unit, and a correction parameter The calculation unit 426A constitutes a correction parameter calculation unit.

The present invention is not limited to the embodiment described above, and various modifications can be made.
For example, in the above-described embodiment, the vane opening is determined based on the turbine model as shown in FIG. 3 in which the front / rear exhaust pressure ratio and the vane opening are associated with each other, but the present invention is not limited to this. For example, the vane opening degree may be determined based on a turbine model in which the upstream exhaust pressure and the vane opening degree are associated with each other.

1. Engine (internal combustion engine)
40, 40A ... ECU
41 ... Target upstream side exhaust pressure calculation section (target value calculation means)
42, 42A ... vane opening degree control unit 421 ... exhaust pressure controller (target value calculation means)
422 ... Vane opening degree determining unit (opening instruction value calculating means)
422A ... Valve opening determining unit (opening instruction value calculating means)
426, 426A ... correction parameter calculation unit (correction parameter calculation means)
8 ... Turbocharger 81 ... Turbine wheel 82 ... Compressor wheel 84 ... Variable vane 85 ... Westgate valve

Claims (6)

A turbocharger comprising: a compressor wheel that pressurizes air sucked into the internal combustion engine; and a turbine wheel that is connected to the compressor wheel and is driven to rotate by blowing exhaust gas discharged from the internal combustion engine;
An exhaust flow rate variable mechanism that changes the flow rate of the exhaust gas blown to the turbine wheel by opening and closing operation, and the opening of the exhaust flow rate variable mechanism is adjusted so that the actual boost pressure matches a predetermined target boost pressure. A supercharging pressure control device for an internal combustion engine to determine,
Target value calculation means for calculating a target value for a predetermined control amount so that the actual boost pressure matches the target boost pressure;
An opening degree instruction that calculates an opening degree instruction value of the exhaust flow variable mechanism according to a target value of the control quantity based on a model that associates the control amount and a predetermined physical quantity with an opening degree of the exhaust flow variable mechanism. A value calculating means;
Based on the model, an opening degree estimated value of the exhaust flow rate variable mechanism according to the measured value of the control amount is calculated, and the opening degree value is matched with the opening degree estimated value and the opening degree instruction value. A boost pressure control device for an internal combustion engine, comprising: a correction parameter calculation unit that calculates a correction parameter for correcting a model of the instruction value calculation unit.   2. The internal combustion engine according to claim 1, wherein the physical quantity includes an exhaust pressure upstream of the turbine wheel, an exhaust temperature upstream of the turbine wheel, and a mass flow rate of exhaust that drives the turbine wheel. Supercharging pressure control device.   The supercharging pressure control device for an internal combustion engine according to claim 1 or 2, wherein the correction parameter calculation means changes a speed at which the correction parameter is updated in accordance with an operating state of the engine.   The boost pressure control device for an internal combustion engine according to claim 1 or 2, wherein the correction parameter calculation means changes a speed at which the correction parameter is updated according to an opening of the exhaust flow rate variable mechanism. The exhaust flow rate variable mechanism includes a variable vane that changes an inlet area of exhaust flowing into the turbine wheel by an opening / closing operation,
The supercharging pressure control device for an internal combustion engine according to any one of claims 1 to 4, wherein the model associates the control amount and a predetermined physical amount with an opening degree of the variable vane. The exhaust flow variable mechanism includes a wastegate valve that opens and closes a bypass passage that bypasses the upstream side and the downstream side of the turbine wheel,
The supercharging pressure control device for an internal combustion engine according to any one of claims 1 to 4, wherein the model associates the control amount and a predetermined physical amount with an opening degree of the waste gate valve.

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