JP2007239515A - Method for estimating steady-state value of characteristic parameter of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for acquiring a steady-state value of a characteristic parameter of an internal combustion engine in a short time, in adapting work. <P>SOLUTION: In the method for estimating a steady-state value of a characteristic parameter of an internal combustion engine, the steady-state value of the characteristic parameter is estimated (S300), based on a convergence characteristic of a predetermined characteristic parameter value of the internal combustion engine, determined in advance when only the predetermined control parameter value of the internal combustion engine is changed, into the steady-state value, and a characteristic parameter transient value measured while changing only the predetermined control parameter value of the internal combustion engine with a predetermined pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for estimating a steady value of a characteristic parameter of an internal combustion engine. More specifically, the present invention relates to a method for estimating the steady value in order to obtain a steady value of the characteristic parameter of the internal combustion engine that is required in an operation for obtaining a suitable value of a control parameter used in the control of the internal combustion engine, that is, a so-called adaptive operation.

  In general, control of an internal combustion engine is performed by adjusting the throttle opening, ignition timing, intake / exhaust valve on / off valve characteristics, fuel injection amount, etc. so as to satisfy the requirements for the characteristics of the internal combustion engine such as generated torque, exhaust emission and fuel consumption. This is done by changing the value of the control parameter. These control parameters have optimum values for each operating state determined by, for example, the engine load (generated torque) and the engine speed in accordance with the request for the internal combustion engine at that time. It is necessary to set the optimum value of the control parameter in advance as a target value.

The optimum value of the control parameter for each operating state is generally a value of a characteristic parameter that represents the characteristics of the internal combustion engine, such as the generated torque and NO _X emission amount, when the control parameter is set to various values. Is obtained by an operation for obtaining an optimum value (that is, an adapted value) of each control parameter for each operating state from the result, that is, an adapted operation.

  In such conforming work, since it is necessary to obtain the characteristic parameter value (that is, the steady value of the characteristic parameter) at the time of steady operation, the operation state is set for each measurement point set by changing the control parameter value. The measurement is performed after waiting for the engine to stabilize, that is, for example, until the torque and the engine speed converge to a substantially constant value. For this reason, it takes a long time to obtain the measurement values of the characteristic parameters at each measurement point.

  On the other hand, in order to perform the adaptation work in a shorter time (that is, in order to obtain the adaptation value), a method of creating a virtual engine model and obtaining the adaptation value using the virtual engine model has been studied. That is, for example, Patent Document 1 discloses a method for obtaining a conformity value in a transient state by creating a transient engine model based on a result of an actual machine test in a transient state, and performing a simulation using the model to obtain a conformance value. It is disclosed.

JP-A-2005-90353 JP 2004-68729 A JP 2002-206456 A

  Meanwhile, while a method using the virtual engine model as described above has been studied, there is still a demand for shortening the time for obtaining the steady value of the characteristic parameter of the internal combustion engine in the adaptation work. The present invention has been made in view of these points, and an object of the present invention is to provide a method for obtaining a steady-state value of a characteristic parameter of an internal combustion engine in a shorter time in an adaptation operation.

  The present invention provides, as means for solving the above problems, a method for estimating a steady value of a characteristic parameter of an internal combustion engine described in each of the claims.

  According to the first aspect of the present invention, the convergence characteristic to the steady value of the characteristic parameter value of the predetermined internal combustion engine when only the value of the control parameter of the predetermined internal combustion engine is changed, and the predetermined internal combustion engine A characteristic parameter of an internal combustion engine is characterized in that a steady value of the characteristic parameter is estimated based on a transient value of the characteristic parameter measured while changing only a value of a control parameter of the engine in a predetermined pattern. A method for estimating a steady value is provided.

  According to the first aspect of the present invention, the steady value of the characteristic parameter is estimated based on the convergence characteristic of the characteristic parameter value to the steady value and the transient value of the characteristic parameter. For this reason, it is not necessary to wait until the operating state of the internal combustion engine is stabilized in order to measure the steady value of the characteristic parameter as in the prior art, and the steady value of the characteristic parameter of the internal combustion engine can be obtained in a shorter time.

  According to a second aspect of the present invention, in the first aspect of the invention, the transient value of the characteristic parameter is measured while changing the value of the control parameter of the predetermined internal combustion engine at a constant speed. Yes. By doing so, it is possible to easily and accurately obtain the steady values of the characteristic parameters of the internal combustion engine.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a representative engine control state among engine control states determined by a control parameter other than the predetermined control parameter of the internal combustion engine as the convergence characteristic. The convergence characteristics required in (1) are used. According to the third aspect of the invention, by using the convergence characteristic obtained in the representative engine control state, the steady value of the characteristic parameter of the internal combustion engine can be obtained more efficiently as a whole.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the representative engine control in an engine control state determined by a control parameter other than the predetermined control parameter of the internal combustion engine is used as the convergence characteristic. A convergence characteristic that is statistically approximated based on the convergence characteristic obtained in the state is used. According to the fourth aspect of the present invention, the convergence characteristic statistically approximated based on the convergence characteristic obtained in the representative engine control state is used, so that the steady-state value of the characteristic parameter of the internal combustion engine is obtained. It can be obtained efficiently and accurately.

  According to the invention described in claim 5, in the invention described in claim 3 or 4, the representative engine control state is determined by an experimental design. According to the fifth aspect of the invention, it is possible to obtain substantially the same operations and effects as the third or fourth aspect of the invention.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the convergence characteristic is a response delay characteristic of the value of the characteristic parameter with respect to a change in the value of the control parameter of the predetermined internal combustion engine. Is included. By doing so, it is possible to easily and accurately obtain the steady values of the characteristic parameters of the internal combustion engine.

  In the invention according to claim 7, in the invention according to any one of claims 1 to 6, when the steady value of the characteristic parameter is estimated, the predetermined value when the transient value of the characteristic parameter is measured is determined in advance. Correction is performed based on setting errors of control parameter values other than those of the internal combustion engine.

  According to the seventh aspect of the invention, it is possible to correct the influence of the setting error of the control parameter value other than the predetermined control parameter of the internal combustion engine, that is, the influence of the measurement condition setting error. Thus, it is possible to achieve both shortening of the measurement condition setting time and improvement in estimation accuracy of the steady value of the characteristic parameter, which is an estimation result based on the measurement.

  According to an eighth aspect of the invention, in the seventh aspect of the invention, the control parameter other than the predetermined control parameter of the internal combustion engine includes an air-fuel ratio, and the characteristic parameter is a generated torque of the internal combustion engine. Thus, when estimating the steady value of the generated torque of the internal combustion engine, correction is performed based on the setting error of the air-fuel ratio when the transient value of the generated torque of the internal combustion engine is measured. .

  According to the eighth aspect of the invention, the influence of the setting error of the air-fuel ratio as the measurement condition can be corrected. Therefore, the estimation result based on the reduction of the setting time of the air-fuel ratio which is the measurement condition and the measurement Thus, it is possible to improve both the estimation accuracy of the steady value of the generated torque of the internal combustion engine.

  The invention described in each claim has a common effect that the steady value of the characteristic parameter of the internal combustion engine can be obtained in a shorter time in the adaptation work.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an internal combustion engine that is an object of the adaptation work and a measurement arithmetic device used for the adaptation work.

  Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a piston that reciprocates in the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is a piston 3 and a cylinder head 4. A combustion chamber formed therebetween, 6 is an intake valve, 7 is an intake port, 8 is an exhaust valve, and 9 is an exhaust port. As shown in FIG. 1, a spark plug 10 is arranged at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is arranged around the inner wall surface of the cylinder head 4. A cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a corresponding intake branch pipe 13, and the surge tank 14 is connected to an intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust manifold 19. The intake valve 6 is provided with a variable valve mechanism 20 for changing the opening / closing valve characteristics of the intake valve 6, that is, the phase angle and the operating angle of the opening / closing valve.

  In general, the control of the internal combustion engine as shown in FIG. 1 is performed so as to satisfy the requirements for torque, exhaust emission, fuel consumption, etc. that change during operation of the internal combustion engine, that is, actual torque, exhaust emission, fuel consumption, etc. This is performed by changing the values of controllable parameters (that is, control parameters) that affect the operating state of the internal combustion engine so that the target torque, the target exhaust emission, the target fuel consumption, and the like are achieved.

  Such a control parameter has an optimum value for each operating state determined by, for example, the engine speed in accordance with a request for the internal combustion engine at that time. For example, with respect to the ignition timing by the spark plug 10, in consideration of the torque, fuel consumption, misfire, etc. of the internal combustion engine, generally, ignition is performed near the minimum advance timing at which the torque becomes the maximum, so-called MBT (Minimum Advance for Best Torque). Is preferably performed. This MBT is not the same for all operating states. For example, when the engine speed is different, the MBT is also at a different time. On the other hand, when it is necessary to increase the temperature of a catalyst (not shown) provided in the exhaust system of the internal combustion engine for exhaust purification of the internal combustion engine, the exhaust gas discharged from the engine body 1 In order to increase the temperature, it is preferable to perform ignition at a timing slightly ahead of the MBT.

  Since it is difficult to calculate the optimum value (that is, the conforming value) of each control parameter for each operating state in accordance with the demand for such an internal combustion engine by only numerical calculation, usually, for each type of internal combustion engine Required by calibration work. Here, the conforming work is a characteristic parameter (a parameter whose value can be changed by changing the value of the control parameter, for each control parameter value, by setting a specific control parameter to various values. Parameter that represents the characteristics of the control parameter), and an optimum value (that is, a suitable value) of the control parameter for each operating state is obtained from the measured values of these characteristic parameters.

  In FIG. 1, in addition to the internal combustion engine that is the subject of the adaptation work, a measurement arithmetic device 40 that measures the value of the characteristic parameter of the internal combustion engine and performs necessary calculations is shown. As shown in the figure, a throttle opening sensor 31 for measuring the opening degree of the throttle valve 18 is attached to the throttle valve 18 and flows through the intake pipe 15 for the internal combustion engine to be subjected to the adaptation work. An air flow meter 32 for measuring the flow rate of air is mounted in the intake pipe 15 upstream of the throttle valve 18. Further, an exhaust gas temperature sensor 33 for measuring the temperature of the exhaust gas discharged from the engine body 1 and an air-fuel ratio sensor 34 for measuring the air-fuel ratio of the exhaust gas discharged from the engine body 1 are attached to the exhaust port or the exhaust manifold 19. . Further, a torque sensor (not shown) for detecting a generated torque that is a driving force of the internal combustion engine is attached to a crankshaft (not shown) of the engine body 1. These sensors 31 to 34 are connected to the measurement calculation device 40, and the measurement calculation device 40 displays, stores, and calculates values of the characteristic parameters measured by the sensors 31 to 34.

  On the other hand, the ignition plug 10, the fuel injection valve 11, the step motor 17 for driving the throttle valve, the variable valve mechanism 20, and the like described above are connected to the measurement arithmetic device 40, and these ignition plugs 10 are driven by the measurement arithmetic device 40. Be controlled. That is, the value of the control parameter is changed by the measurement arithmetic device 40.

  By the way, the measurement of the values of various characteristic parameters in the adaptation work is usually performed at each measurement point with various control parameters set as described above. Here, a measurement point is specified by a combination of setting values of each control parameter, and one measurement point corresponds to one combination of setting values for each control parameter. That is, each set measurement point corresponds to each engine control state that is the state of the internal combustion engine specified by the combination of the values of the control parameters.

  Specifically, for example, measurement is sequentially performed at measurement points where only one control parameter is changed at constant intervals (the values of other control parameters are constant). In this case, since it is necessary to obtain the value of the characteristic parameter at the time of steady operation (that is, the steady value of the characteristic parameter), the operation state is stabilized at each measurement point set by changing the value of the control parameter. Measurement is performed after waiting until the torque and the engine speed converge to a substantially constant value. For this reason, it takes a long time to obtain the measured value of the characteristic parameter at each measurement point.

  Therefore, in the present embodiment, in consideration of the above, the measurement calculation device 40 performs a method as described below to estimate the steady-state value of the characteristic parameter of the internal combustion engine. The steady value of the characteristic parameter of the internal combustion engine is obtained in a shorter time.

  In other words, in this method, the convergence characteristic to the steady value of the characteristic parameter value of the predetermined internal combustion engine when only the value of the control parameter of the predetermined internal combustion engine is changed, and the above predetermined value. The steady value of the characteristic parameter is estimated based on the transient value of the characteristic parameter measured while changing only the value of the control parameter in a predetermined pattern.

  More specifically, as shown in FIG. 2, the method includes a step of obtaining the convergence characteristic (step 100), a step of measuring a transient value of the characteristic parameter (step 200), and a steady state of the characteristic parameter. A step of estimating a value (step 300).

  First, referring to FIG. 3, the step of obtaining the convergence characteristic (step 100) will be described in more detail. FIG. 3 is a flowchart showing details of the step (step 100) for obtaining the convergence characteristic. As shown in FIG. 3, at this stage, first, the target control parameter Xa and characteristic parameter Ya are selected (step 101). That is, it determines which control parameter suitable value is to be obtained for which characteristic parameter. More specifically, examples of the target control parameter Xa that can be selected here include air-fuel ratio, on-off valve characteristics of the intake valve 6, ignition timing, and the like. Examples of the target characteristic parameter Ya include exhaust gas temperature. , Torque, fuel consumption and the like. In other embodiments, when the on-off valve characteristic of the exhaust valve 8 is variable, the on-off valve characteristic of the exhaust valve 8 can also be selected as the target control parameter Xa.

  Further, when the steady value of the characteristic parameter is estimated by the method of the present embodiment, the value of Ya is a primary expression or a quadratic value of the value of Xa between the value of the target control parameter Xa and the value of the target characteristic parameter Ya. It is known that the steady value of the characteristic parameter can be estimated with high accuracy when there is a relationship that can be expressed by the equation. Therefore, it is desirable to select the target control parameter Xa and the target characteristic parameter Ya in consideration of this. In this respect, changes in the engine speed complexly affect the values of various characteristic parameters due to pulsation phenomena in the intake pipe and the exhaust pipe. Therefore, it is not desirable to select the engine speed as the target parameter Xa.

  As for the throttle opening, since the relationship between the throttle opening and the intake air amount, that is, the intake air mass KL per stroke, is non-linear, the relationship with the values of various characteristic parameters tends to be complicated, and the above-mentioned The target control parameter Xa is not desirable. Therefore, as a control parameter representing such a load, the intake air amount, that is, the intake air mass KL per stroke is selected as the target control parameter Xa. In this case, when the transient value of the target characteristic parameter Ya is measured by changing the value of the target control parameter Xa at a constant speed as described later, the relationship between the throttle opening and the KL is obtained in advance. The transient value is measured by controlling the throttle opening so that the KL changes at a constant rate.

  When the target control parameter Xa and the target characteristic parameter Ya are selected in step 101, the process proceeds to step 102. In step 102, a matching region that is the range of the engine control state in which matching is performed is determined. Here, the engine control state is specified by a combination of values of each control parameter including the target control parameter Xa, and the applicable region includes a settable range of each control parameter, a range in which stable engine operation and measurement can be performed, and the like. Decided in consideration. More specifically, for example, a knock limit, a catalyst temperature limit, a variable valve system setting limit, and the like are taken into consideration.

  When the matching region is determined in step 102, the process proceeds to step 103, and the representative engine control state Pi is determined. In this embodiment, each representative engine control state Pi is specified by each combination of control parameter values excluding the target control parameter Xa. Here, the representative engine control state Pi is determined by an experimental design method, for example, an optimal design method.

  FIG. 4 is a diagram illustrating an example of a case where the representative engine control state Pi is determined when the control parameters that define the adaptation region are Xa, Xb, and Xc and the target control parameter is Xa. In this figure, the horizontal axis represents the control parameter Xb, and the vertical axis represents the control parameter Xc. Although not shown, an axis representing the target control parameter Xa is assumed in a direction perpendicular to both the axes (that is, a direction perpendicular to the paper surface). A region Sc indicated by a dotted line in the drawing is a cross section on the Xb-Xc plane of the matching region represented in three dimensions of Xa, Xb, and Xc. In this example, four representative engine control states P1, P2, P3, and P4, each of which is specified by a combination of the values of the control parameters Xb and Xc, are determined in the region Sc by the above-described optimal planning method.

  When the representative engine control state Pi is determined in step 103, the process proceeds to step 104. In step 104, a convergence characteristic with respect to a change in the value of the target control parameter Xa of the value of the target characteristic parameter Ya in each representative engine control state Pi is obtained. In this embodiment, a response delay characteristic with respect to a change in the value of the target control parameter Xa of the value of the target characteristic parameter Ya is obtained as the convergence characteristic.

  More specifically, for example, in each representative engine control state Pi, the value of the target control parameter Xa is changed stepwise, and the subsequent change in the value of the target characteristic parameter Ya is measured, and based on the transient response change. Response delay characteristics. That is, for example, the transient response change of the measured value of the target characteristic parameter Ya is assumed to be a first-order lag system, and the time constant T as a characteristic value indicating the response delay characteristic is obtained.

More specifically, in the present embodiment, in each representative engine control state Pi, the value of the target control parameter Xa is changed stepwise to measure a transient response change in the value of the target characteristic parameter Ya, and the transient response change is measured. Assuming a first-order lag system (Ya (t) = K (1-e ^{(-t / T)} ), t: time, K: proportional gain, T: time constant), steepest descent using the least squares method as an evaluation function The proportional gain K and the time constant T are obtained using the method. FIG. 5 shows an example of a case where the value of the target control parameter Xa is changed stepwise in the representative engine control state P1, and the transient response change of the value of the target characteristic parameter Ya is measured. The transient response change of the value of the target characteristic parameter Ya is assumed to be a first-order lag system (Ya (t) = K (1−e ^{(−t / T)} )).

  When the convergence characteristic in each representative engine control state Pi is obtained in step 104 (that is, the time constant T as a response delay characteristic with respect to the change of the target control parameter Xa of the target characteristic parameter Ya). In this embodiment, the process further proceeds to step 105. In step 105, based on the convergence characteristic in each representative engine control state Pi obtained in step 104, each specified by a combination of values of each control parameter excluding the target control parameter Xa in the applicable region. The convergence characteristics in the engine control state are approximated statistically.

  That is, in the example shown in FIG. 4, based on the convergence characteristics in each representative engine control state P1, P2, P3, P4 obtained, the control parameter Xb in the region Sc indicated by the dotted line in the figure and Convergence characteristics in each engine control state, each identified by a combination of Xc values, are statistically approximated.

  More specifically, for example, based on the relationship between the values of the control parameters Xb and Xc in the representative engine control states P1, P2, P3, and P4 and the time constant T by a statistical method, A map in which a time constant T corresponding to an arbitrary engine control state indicated by a combination of the control parameters Xb and Xc is obtained or a relational expression is derived. In this way, by using this map or relational expression, the time constant T corresponding to an arbitrary engine control state indicated by the combination of the control parameters Xb and Xc in the region Sc can be obtained. .

  In step 105, when the convergence characteristics in each engine control state identified by the combination of the values of the control parameters excluding the target control parameter Xa within the adaptive region are statistically approximated and predicted as shown in FIG. Proceeding to step 200, the transient value of the target characteristic parameter Ya is measured.

  This measurement is performed in the engine control state specified by the combination of the values of the respective control parameters excluding the target control parameter Xa (that is, the values of control parameters other than the target control parameter Xa are fixed). This is performed by measuring the value of the target characteristic parameter Ya while changing the value of the parameter Xa in a predetermined pattern. In the present embodiment, the measurement of the transient value of the target characteristic parameter Ya is performed while changing the value of the target control parameter Xa at a constant speed.

  FIG. 6 measures the value of the target characteristic parameter Ya while increasing the value of the target control parameter Xa at a constant speed with the control parameters Xb and Xc other than the target control parameter Xa being set to constant values b and c, respectively. The time-dependent change of the value of the target control parameter Xa and the target characteristic parameter Ya is shown. In this figure, the horizontal axis represents time t and is a transient value in which the value of Ya indicated by the solid line Ya1 is measured.

  When the transient value of the target characteristic parameter Ya is measured in step 200, the process proceeds to step 300. In step 300, a steady value of the target characteristic parameter Ya is estimated based on the convergence characteristic obtained in step 100 and the transient value measured in step 200.

  More specifically, using the example shown in FIG. 6, the steady value of the target characteristic parameter Ya is estimated as follows. That is, first, in FIG. 6, the measured transient value of the target characteristic parameter Ya (solid line Ya1) is the engine control state in which the transient value is measured, that is, the control parameter Xb = b and the control parameter Xc = c. Shifting to the early side by the time constant T in the case of a certain engine control state. A value obtained by shifting the transient value (solid line Ya1) of the target characteristic parameter Ya to the earlier side by the time constant T is indicated by a dotted line Ya2 in FIG.

  As can be understood from the above description, the value of the target characteristic parameter Ya indicated by the dotted line Ya2 is a value considering the response delay. Therefore, the target characteristic parameter Ya indicated by the dotted line Ya2 is used. Is estimated to be a steady value of the target characteristic parameter Ya when the value of the target control parameter Xa is changed to a corresponding value.

  FIG. 7 is a redraw of FIG. 6 to show the relationship between the value of the target control parameter Xa and the value of the target characteristic parameter Ya. The solid line Ya3 and the dotted line Ya4 in FIG. 7 are the solid lines in FIG. This corresponds to Ya1 and dotted line Ya2. That is, the value indicated by the dotted line Ya4 in FIG. 7 is the steady value of the target characteristic parameter Ya when the target control parameter Xa is set to each corresponding value when the control parameter Xb is b and Xc is c. Presumed. Note that the value of the target characteristic parameter Ya indicated by the one-dot chain line Ya5 in FIG. 7 is a steady value of the actually measured target characteristic parameter Ya, and the steady value is accurately estimated by the method of the present embodiment. I understand that.

  As described above, according to the method of the present embodiment, the steady value of the characteristic parameter can be estimated based on the convergence characteristic of the characteristic parameter value to the steady value and the transient value of the characteristic parameter. For this reason, it is not necessary to wait until the operating state of the internal combustion engine is stabilized in order to measure the steady value of the characteristic parameter as in the prior art, and the steady value of the characteristic parameter of the internal combustion engine can be obtained in a shorter time.

  In the method of this embodiment, the transient value of the characteristic parameter is measured while changing the value of the target control parameter at a constant speed. By doing so, it is possible to easily and accurately obtain the steady values of the characteristic parameters of the internal combustion engine.

  Further, in the method of the present embodiment, as the convergence characteristic, the value of the target control parameter is the value of the characteristic parameter obtained in the representative engine control state among the engine control states determined by the control parameters other than the target control parameter. The convergence characteristic statistically approximated based on the convergence characteristic with respect to a change is used. By doing so, it is possible to efficiently and accurately obtain the steady values of the characteristic parameters of the internal combustion engine.

  In another embodiment, as the convergence characteristic, the value of the target control parameter is the value of the characteristic parameter obtained in the representative engine control state among the engine control states determined by control parameters other than the target control parameter. Convergence characteristics with respect to changes may be used. By doing so, it is possible to obtain a steady value of the characteristic parameter of the internal combustion engine more efficiently.

  As can be seen from FIGS. 6 and 7, when the steady value of the target characteristic parameter Ya is estimated by the method of the present embodiment, the estimated value of the steady value is immediately after the start of the transient value measurement of the target characteristic parameter Ya. As for the portion corresponding to the measured value, the estimation accuracy of the steady value may be lower than that of the other portions. This is because a response delay occurs immediately after the start of the transient value measurement, and in order to suppress such a decrease in estimation accuracy, a predetermined time Tw after the start of the transient value measurement is used. It is preferable not to use measured values. The predetermined time Tw may be set as appropriate based on the required estimation accuracy. For example, assuming that a first-order lag system is used and the measurement value up to 95% response is not used, the following calculation is performed. After the start of the transient value measurement, a measured value within a time corresponding to 3T (three times the time constant T) is not used.

Ya (t) = K (1-e ^{(-t / T)} ) = 0.95K
t = T · log 0.05≈2.9957T≈3.0T

  In the example shown in FIGS. 6 and 7, there is a relationship that the value of Ya can be substantially expressed by a linear expression of the value of Xa between the value of the target control parameter Xa and the value of the target characteristic parameter Ya. However, as described above, there is a relationship between the value of the target control parameter and the value of the target characteristic parameter so that the value of the target characteristic parameter can be substantially expressed by a quadratic expression of the value of the target control parameter. However, the steady value of the target characteristic parameter can be accurately estimated by the method of the present embodiment.

  8 and 9 each show a case where the value of the target characteristic parameter and the value of the target characteristic parameter have a relationship that allows the value of the target characteristic parameter to be substantially expressed by a quadratic expression of the value of the target control parameter. FIG. 8 is a diagram corresponding to FIGS. 6 and 7. That is, here, there is a relationship between the value of the target control parameter Xa and the value of the target characteristic parameter Yb so that the value of the target characteristic parameter Yb can be substantially expressed by a quadratic expression of the value of the target control parameter Xa.

  FIG. 8 shows that the control parameter Xb and Xc other than the target control parameter Xa are set to constant values b and c, respectively, and the value of the target characteristic parameter Yb is increased while increasing the value of the target control parameter Xa at a constant speed. The time-dependent change of the value of the target control parameter Xa and the target characteristic parameter Yb when measured is shown. In this figure, the value of Yb indicated by the solid line Yb1 is the measured transient value. A dotted line Yb2 indicates the measured transient value (solid line Yb1) of the target characteristic parameter Yb. The engine control state in which the transient value is measured, that is, the engine having the control parameter Xb = b and the control parameter Xc = c. This is shifted to the earlier side by the time constant T in the control state.

  On the other hand, FIG. 9 is a redraw of FIG. 8 to show the relationship between the value of the target control parameter Xa and the value of the target characteristic parameter Yb. The solid line Yb3 and the dotted line Yb4 in FIG. Correspond to the solid line Yb1 and the dotted line Yb2. That is, the value indicated by the dotted line Yb4 in FIG. 9 is the steady value of the target characteristic parameter Yb when the target control parameter Xa is set to each corresponding value when the control parameter Xb is b and Xc is c. Presumed. The value of the target characteristic parameter Yb indicated by the alternate long and short dash line Yb5 in FIG. 9 is a steady value of the actually measured target characteristic parameter Yb, and the steady value is accurately estimated by the method of this embodiment. I understand that.

  By the way, as is clear from the above description, when the steady value of the target characteristic parameter is estimated by the method as described above, in order to increase the accuracy of the estimated steady value, the estimated steady value It is necessary to measure the transient value that is the basis of This can be realized only by accurately setting the engine control state at the time of measuring the transient value.

  On the other hand, if the engine control state is to be set accurately, it takes a long time to set the engine control state. As a result, it takes time to measure the transient value of the target characteristic parameter, and as a whole the steady value (estimated) Value) may not be sufficiently shortened.

  Therefore, in another embodiment of the present invention, the influence of setting errors of control parameter values other than the target control parameter on the value of the target characteristic parameter is examined in advance, and the steady value of the target characteristic parameter is estimated. In this case, correction is performed based on setting errors of control parameter values other than the target control parameter when the transient value of the target characteristic parameter is measured.

  By doing so, it is possible to later correct the influence of the setting error of the values of the control parameters other than the target control parameter, that is, the influence of the setting error of the engine control state which is a measurement condition when measuring the transient value. Therefore, it is possible to reduce both the set time of the engine control state and improve the estimation accuracy of the steady value of the target characteristic parameter, which is an estimation result based on measurement.

  As is apparent from the above description, in this method, the influence of the setting error of the value of the control parameter on the value of the target characteristic parameter is examined in advance, and the control parameter with respect to the estimated value of the steady value of the target characteristic parameter is determined. It is necessary to obtain a value (that is, a basic correction value) that serves as a base for correction based on the setting error of the value. FIG. 10 is a flowchart showing a procedure for obtaining the basic correction value in the present embodiment.

  As shown in FIG. 10, when obtaining the basic correction value in the present embodiment, first, in step 401, an experimental region that is the range of the engine control state that requires the basic correction value is determined. This experimental region may be determined in substantially the same manner as in the case of the adaptation region described above. For example, when the target characteristic parameter is the generated torque of the internal combustion engine, the range of the ignition timing as one of the control parameters is It is good also as only the range of MBT vicinity mentioned above.

  When the experimental region is determined in step 401, the process proceeds to step 402, and the representative engine control state Qi is determined. Here, each representative engine control state Qi is specified by each combination of values of each control parameter including the target control parameter Xa. The determination of the representative engine control state Qi is performed in substantially the same manner as the determination of the representative engine control state Pi described above, and an experimental design method, for example, an optimal design method is used. Here, in particular, the representative engine control state Qi includes an engine control state in which the value of KL (mass of intake air per stroke) as a control parameter representing the load is different.

  When the representative engine control state Qi is determined at step 402, the routine proceeds to step 403. In step 403, the fluctuation range of the control parameter (that is, the setting control parameter) Xb to be examined for the influence of the setting error is determined. That is, this fluctuation range is the magnitude of an error that can be assumed when the value of the setting control parameter Xb is set as the measurement condition in the transient value measurement in step 200 described above. For example, in the case of an internal combustion engine that normally performs combustion at the stoichiometric air-fuel ratio, and considering the air-fuel ratio AF as the set control parameter Xb, the fluctuation range is about the stoichiometric air-fuel ratio ± 0.5.

  When the fluctuation range of the setting control parameter Xb is determined in step 403, the process proceeds to step 404. In step 404, in each representative engine control state Qi, the value of the set control parameter Xb is changed by the fluctuation range around the representative engine control state Qi, and the value of the target characteristic parameter Ya (that is, Yai) is set. It is measured.

  In the following step 405, for each representative engine control state Qi, the difference ΔXb from the target value of the value of the set control parameter Xb (that is, the value of the set control parameter Xb to be set in each representative engine control state Qi). And the difference ΔYai between the measured value Yai of the target characteristic parameter Ya and the value when the set control parameter Xb is set as the target value, are approximated by a linear expression. As a result, the slope Ei of each approximate linear expression is calculated (step 406).

  FIG. 11 shows an example in which measurement is performed in the vicinity of six representative engine control states Qi, where the set control parameter Xb is the air-fuel ratio AF and the target characteristic parameter Ya is the generated torque TQ of the internal combustion engine. That is, the horizontal axis represents the difference ΔAF from the target value of the air-fuel ratio AF, and the vertical axis represents the difference ΔTQ from the value when the air-fuel ratio AF of the generated torque TQ value is the target value. Each of the six straight lines shown in (1) corresponds to an approximate linear expression obtained based on values measured in the vicinity of each representative engine control state Qi.

  When the slope Ei of each approximate linear expression is calculated in step 406, the process proceeds to step 407. In step 407, the slope Eimax obtained corresponding to the representative engine control state having the largest KL in the representative engine control state Qi and the slope Eimin obtained corresponding to the representative engine control state having the smallest KL. It is determined whether or not the difference ΔE (= Eimax−Eimin) is larger than a predetermined reference value R. This reference value R is determined based on the accuracy required for the estimated steady value of the target characteristic parameter Ya finally obtained, and the reference value R decreases as the required accuracy increases.

  If it is determined in step 407 that the difference ΔE is less than or equal to the reference value R, the process proceeds to step 408. When the process proceeds to step 408, the average value of the gradient Ei obtained corresponding to each representative control state Qi is obtained, and that value is used as the basic correction value. That is, in this case, the setting error of the setting control parameter Xb in the transient value measurement in step 200 described above is obtained, and the value obtained by the transient value measurement is obtained by multiplying the basic correction value by the setting error. Make corrections.

  On the other hand, when it is determined in step 407 that the difference ΔE is larger than the reference value R, the process proceeds to step 409, and the slope Ei obtained corresponding to each representative control state Qi is set to the above-described gradient Ei in each representative control state Qi. A value Fi (= Ei / KLi) divided by the value of KL (that is, KLi) is calculated. That is, this process is performed when the influence of the change in the value of KL on the value of the characteristic parameter is large. FIG. 12 is a diagram similar to FIG. 11, and the value represented by the vertical axis is a value (ΔTQ / KL) obtained by dividing the above-described difference ΔTQ by the value of KL in the corresponding representative engine control state. It is.

  Following step 409, the process proceeds to step 410. Then, an average value of the values Fi obtained corresponding to each representative control state Qi is obtained, and the value is used as a basic correction value. That is, in this case, a setting error of the setting control parameter Xb in the transient value measurement in the above-described step 200 is obtained, and the value obtained by the transient value measurement is used as the basic correction value. Correction is made with a value obtained by multiplying the value of KL at the time of value measurement.

  In the above description, the average value of Ei or the average value of Fi is used as the basic correction value. However, in other embodiments, the value of Ei or Fi is used as the corresponding representative engine control. It may be used as a basic correction value for the state Qi and the surrounding engine control state.

  By the way, the method for estimating the steady value of the characteristic parameter by basically correcting the transient value of the measured characteristic parameter in consideration of the convergence characteristic, more specifically the response delay characteristic has been described above. The steady value of the characteristic parameter can be simply estimated by another method as described below.

  That is, first, only the value of the target control parameter Xa is changed in the same pattern (for example, a constant speed) within a predetermined range and is made to reciprocate once, and the transient value of the target characteristic parameter Ya at that time is measured. Next, an intermediate value between the transient value of the target characteristic parameter Ya corresponding to the forward path portion of the change in the target control parameter Xa and the transient value of the target characteristic parameter Ya corresponding to the backward path portion of the change in the target control parameter Xa is obtained. It is obtained and used as the estimated steady value of the target characteristic parameter Ya.

  In practice, the estimation accuracy may not be sufficient with this method, but the steady values of the characteristic parameters can be estimated very easily. Implementation is possible.

FIG. 1 is a diagram illustrating an internal combustion engine that is a target of a conforming work and a measurement arithmetic device used for the conforming work. FIG. 2 is a flowchart showing the entire method according to an embodiment of the present invention. FIG. 3 is a flowchart showing details of the step of obtaining the convergence characteristic in step 100 of FIG. FIG. 4 is a diagram for explaining the compatible region and the representative engine control state Pi. FIG. 5 is a diagram for explaining a method for obtaining the convergence characteristic in the representative engine control state Pi in step 104 of FIG. FIG. 6 is a graph showing changes over time in the values of the control parameter Xa and the characteristic parameter Ya when the value of the characteristic parameter Ya is measured while increasing the value of the control parameter Xa at a constant speed. A dotted line Ya2 indicates the characteristic parameter Ya. The transient value (solid line Ya1) is shifted to the earlier side by the time constant. FIG. 7 is a redraw of FIG. 6 to show the relationship between the value of the control parameter Xa and the value of the characteristic parameter Ya, and the solid line Ya3 and the dotted line Ya4 correspond to the solid line Ya1 and the dotted line Ya2 in FIG. 6, respectively. . FIG. 8 is a graph showing changes over time in the values of the control parameter Xa and the characteristic parameter Yb when the value of the characteristic parameter Yb is measured while increasing the value of the control parameter Xa at a constant speed. A dotted line Yb2 indicates the characteristic parameter Yb. The transient value (solid line Yb1) is shifted earlier by the time constant. FIG. 9 is a redraw of FIG. 8 to show the relationship between the value of the control parameter Xa and the value of the characteristic parameter Yb. The solid line Yb3 and the dotted line Yb4 correspond to the solid line Yb1 and the dotted line Yb2 in FIG. 8, respectively. . FIG. 10 is a flowchart showing a procedure for obtaining the basic correction value. FIG. 11 is a diagram showing approximation by the linear expression performed in step 405 of FIG. 10, and the six representative engine control states with the set control parameter Xb as the air-fuel ratio AF and the characteristic parameter Ya as the generated torque TQ of the internal combustion engine. This is an example when measurement is performed in the vicinity of Qi. The horizontal axis represents the difference ΔAF from the target value of the air-fuel ratio AF, and the vertical axis represents the difference ΔTQ from the value when the air-fuel ratio AF of the generated torque TQ value is the target value. FIG. 12 is a diagram similar to FIG. 11, wherein the value represented by the vertical axis is obtained by dividing the difference ΔTQ by the value of KL (mass of intake air per stroke) in the corresponding representative engine control state (ΔTQ). / KL).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 6 Intake valve 8 Exhaust valve 10 Spark plug 11 Fuel injection valve 18 Throttle valve 31 Throttle opening sensor 32 Air flow meter 33 Exhaust temperature sensor 34 Air-fuel ratio sensor 40 Measurement arithmetic device

Claims (8)

  The convergence characteristic of the predetermined characteristic parameter value of the internal combustion engine to the steady value when only the predetermined control parameter value of the internal combustion engine is changed, and only the predetermined control parameter value of the internal combustion engine are determined in advance. A method for estimating a steady value of a characteristic parameter of an internal combustion engine, wherein the steady value of the characteristic parameter is estimated based on a transient value of the characteristic parameter measured while changing in a predetermined pattern.   2. The method according to claim 1, wherein the transient value of the characteristic parameter is measured while changing the value of the control parameter of the predetermined internal combustion engine at a constant speed.   The convergence characteristic obtained in a representative engine control state among engine control states determined by control parameters other than the predetermined control parameter of the internal combustion engine is used as the convergence characteristic. The method described in 1.   As the convergence characteristic, a convergence characteristic statistically approximated based on the convergence characteristic obtained in the representative engine control state among the engine control states determined by the control parameters other than the predetermined control parameter of the internal combustion engine is used. 4. The method according to any one of claims 1 to 3, characterized in that:   5. The method according to claim 3, wherein the representative engine control state is determined by an experimental design method.   6. The convergence characteristic according to claim 1, wherein the convergence characteristic includes a response delay characteristic of the characteristic parameter value with respect to a change in the predetermined control parameter value of the internal combustion engine. the method of.   When the steady value of the characteristic parameter is estimated, correction based on a setting error of a control parameter value other than the predetermined control parameter of the internal combustion engine when the transient value of the characteristic parameter is measured is performed. A method according to any one of the preceding claims, characterized in that The control parameter other than the predetermined control parameter of the internal combustion engine includes an air-fuel ratio, and the characteristic parameter is a generated torque of the internal combustion engine,
The correction based on an air-fuel ratio setting error when measuring a transient value of the generated torque of the internal combustion engine is performed when estimating a steady value of the generated torque of the internal combustion engine. 8. The method according to 7.

Images