JP2006342710A - Method for measuring characteristic parameter of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring a characteristic parameter capable of acquiring a measurement value of the characteristic parameter with relatively high reliability, by actually measuring each measure point while suppressing measurement manhours. <P>SOLUTION: A value of control parameters is set to be variable, and a value of a characteristic parameter, when steady operation is performed with a control parameter, is measured for each value of the control parameters. In the method for measuring the characteristic parameter, the value of the characteristic parameter is measured for each cylinder in such a state that at least one value of the control parameter is different for each cylinder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for measuring characteristic parameters of an internal combustion engine.

In general, control of an internal combustion engine changes the values of control parameters such as throttle opening, ignition timing, intake / exhaust valve on / off valve characteristics, and fuel injection amount so as to satisfy demands on torque, emission, fuel consumption, and the like. Is done by. Such control parameters have optimum values for each engine operating state (for example, engine load and engine speed). The optimum value of the control parameter for each engine operating state is generally set to various values for each engine operating state, and the characteristic parameters such as torque, fuel injection amount or NO _X emission amount at that time are set. From the measured value, the optimum value of the control parameter is obtained by so-called adaptation work.

  In such conforming work, since it is necessary to measure the value of the characteristic parameter at the time of steady operation, after waiting until the engine operating state is stabilized at each measurement point, for example, the torque, the engine speed, etc. are substantially constant. Wait until it converges to the value before measuring. For this reason, it takes time to obtain the measurement values of the characteristic parameters at each measurement point. In addition, in order to increase the matching accuracy, measurement is required at many measurement points, and in some cases, the number of measurement points reaches several thousand to several hundred thousand. For this reason, the measurement man-hour of the whole conforming work becomes enormous.

  Therefore, the interval between each measurement point is increased, that is, the difference in the control parameter value between each measurement point is increased to reduce the number of measurement points, and the model formula is obtained based on the measurement value of the characteristic parameter. It has been proposed to estimate a characteristic parameter value for each control parameter value between measurement points based on an equation (Patent Document 1). Thereby, a measurement man-hour can be reduced.

JP 2002-206456 A JP 2004-68729 A

  However, even if the interval between the measurement points is increased in this way, measurement is performed at each measurement point, and therefore the number of measurement steps cannot be sufficiently reduced. On the other hand, since the value of a characteristic parameter is estimated using a model formula between measurement points, the reliability is not so high. Therefore, in order to increase the reliability of the characteristic parameter value, it is necessary to actually perform measurement at each measurement point to obtain the value.

  Accordingly, an object of the present invention is to provide a characteristic parameter measurement method capable of obtaining a measurement value of a relatively reliable characteristic parameter by actually performing measurement at each measurement point while reducing the number of measurement steps. is there.

In order to solve the above-described problem, in the first invention, the characteristic parameter when the value of the control parameter is set to various values and the steady operation is performed with the value of the control parameter for each value of the control parameter. In the method for measuring the characteristic parameter of the internal combustion engine that measures the value of the internal combustion engine, the value of the characteristic parameter is measured for each cylinder in a state where the value of at least one control parameter is different among the cylinders.
According to the first aspect, it is possible to acquire characteristic parameter values in a plurality of control states having different control parameter values in one measurement. For example, for a four-cylinder internal combustion engine, characteristic parameter values in four control states with different control parameter values can be obtained by a single measurement. For this reason, it becomes possible to reduce a measurement man-hour. On the other hand, since the value of the characteristic parameter in each control state is obtained by actual measurement, the value of the characteristic parameter can be obtained with higher accuracy than in the case of obtaining the value of the characteristic parameter between measurement points by estimation.
It should be noted that “the value of the control parameter is different among cylinders” is described in addition to the case where the value of the control parameter is different for each cylinder and the control parameter for at least one of all the cylinders. When the value of is different from the value of the control parameter for the other cylinders, for example, in the case of four cylinders, a case where the value is different by two cylinders is also included.
The control parameter is a controllable parameter that affects the engine operating state, and particularly means a parameter that can be set to a different value between cylinders during engine operation. Examples of control parameters include ignition timing, intake valve or exhaust valve phase angle or operating angle, fuel injection amount, air-fuel ratio, and the like. On the other hand, the characteristic parameter is a parameter whose value can be changed by changing the control parameter and represents the characteristic of the internal combustion engine. For example, torque, air-fuel ratio, exhaust gas discharged from the engine body, and the like. Temperature (hereinafter referred to as “exhaust temperature”), exhaust emission, and the like. As can be seen from the above description, the same parameter can correspond to both the control parameter and the characteristic parameter. For example, the air-fuel ratio may be used as a control parameter or may be used as a characteristic parameter.

In a second invention, in the first invention, the value of the characteristic parameter is measured for each cylinder in a state where the value of the control parameter is the same for all the cylinders, and the characteristic parameter measured in this state is measured. When there is a variation among cylinders, the characteristic parameter value for each cylinder measured with the value of at least one control parameter different between the cylinders is corrected based on the variation between the cylinders. I did it.
If there is a manufacturing error between the cylinders, an error will occur in the measured value of the characteristic parameter even if the control parameter value is the same for all cylinders. In an internal combustion engine having three or more cylinders, the in-cylinder temperature or the like differs between a cylinder positioned at the end of the cylinders arranged in a row and a cylinder positioned in the middle. According to the second invention, the measured value of the characteristic parameter in a state where the value of the control parameter is different for each cylinder based on the variation between the cylinders in the state where the value of the control parameter is the same for all the cylinders. Therefore, the measured value of the characteristic parameter can be made more accurate.

  According to the present invention, characteristic parameter values in a plurality of control states having different control parameter values can be obtained by a single measurement, and the characteristic parameter values in each control state can be obtained by actual measurement. It is possible to obtain a measurement value of a characteristic parameter with relatively high reliability by actually performing measurement at each measurement point while reducing the number of measurement steps.

  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 an adaptation operation described later and a measuring device used for the adaptation operation.

  Referring to FIG. 1, the engine body 1 includes a plurality of, for example, four cylinders 1a. Each cylinder 1 a is connected to a surge tank 3 via a corresponding intake branch pipe 2, and the surge tank 3 is connected to an air cleaner 5 via an intake pipe 4. A throttle valve 7 driven by an actuator 6 is disposed in the intake duct 4. Each cylinder 1 a is connected to a catalytic converter 11 having an exhaust purification catalyst 10 built in via an exhaust manifold 8 and an exhaust pipe 9. In the internal combustion engine shown in FIG. 1, combustion is performed in the order of # 1- # 3- # 4- # 2.

  Referring to FIG. 2 showing details of each cylinder 1a, 12 is a cylinder block, 13 is a cylinder head fixed on the cylinder block 12, 14 is a piston reciprocating in the cylinder block 12, and 15 is a piston 14 and cylinder head 13. , 16 is a pair of intake ports, 17 is a pair of intake valves, 18 is a pair of exhaust ports, and 19 is a pair of exhaust valves. A spark plug 20 is disposed at the center of the inner wall surface of the cylinder head 13, and a fuel injection valve 21 is disposed around the inner wall surface of the cylinder head 13. The intake valve 17 and the exhaust valve 19 of each cylinder are opened and closed by an intake valve drive device 22 and an exhaust valve drive device 23, respectively. The intake valve drive device 22 and the exhaust valve drive device 23 are respectively driven by an intake valve 17 and an exhaust valve 19. The intake valve 17 and the exhaust valve 19 can be opened and closed while changing the phase angle and the working angle.

In general, the control of an internal combustion engine as shown in FIGS. 1 and 2 is performed by controlling torque, exhaust emission (for example, nitrogen oxide (NO _x ) in exhaust gas, carbon monoxide (CO ) And hydrocarbon (HC) content) and fuel consumption, etc., that is, engine operation so that the actual torque, exhaust emission and fuel consumption become the target torque, target exhaust emission and target fuel consumption, etc. This is done by changing the value of a controllable parameter (hereinafter referred to as “control parameter”) that affects the state.

  Such control parameters have optimum values for each request for the internal combustion engine and engine operating conditions (for example, engine load and engine speed). For example, with regard to the ignition timing by the spark plug 20, in consideration of the torque, fuel consumption, misfire, etc. of the internal combustion engine, generally, ignition is performed in the vicinity of a so-called MBT (Minimum Advance for Best Torque) at which the torque becomes maximum. Is preferably performed. This MBT is not the same time for all engine operating states. For example, when the engine speed is different, the MBT is also different. On the other hand, when it is necessary to raise the temperature of the exhaust purification catalyst 10 for exhaust purification of the internal combustion engine, the temperature of the exhaust gas discharged from the engine body 1 (hereinafter referred to as “exhaust temperature”). ) Is preferably performed at a timing that is somewhat advanced from the MBT.

  Since it is difficult to calculate the optimum value of the control parameter for such a demand for the internal combustion engine and the engine operating state only by numerical calculation or the like, it is usually obtained by adaptation work for each type of the internal combustion engine. Here, the conforming work is a characteristic parameter (control parameter) when a specific control parameter is set to various values for each engine operating state and steady operation is performed with this value for each value of the control parameter. The value of a parameter whose value can be changed by changing the value of the engine and indicating the characteristic of the internal combustion engine) is measured, and the optimum value of the control parameter for each engine operating state is obtained from the measured value of the characteristic parameter. Means work.

  FIG. 1 shows a characteristic parameter measuring device 30 of the internal combustion engine in addition to the internal combustion engine to be subjected to the adaptation work. As shown in the figure, a throttle opening sensor 31 for measuring the opening degree of the throttle valve 7 is attached to the throttle valve 7 and flows through the intake pipe 4 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 4 on the upstream side of the throttle valve 7. Further, an exhaust 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 provided for each exhaust branch pipe of the exhaust manifold 8. Mounted on. Further, a torque sensor (not shown) for detecting torque that is a driving force of the internal combustion engine is attached to a crankshaft (not shown) of the engine body 1, and the cylinder head 13 has a combustion chamber for each cylinder. An in-cylinder pressure sensor (not shown) for measuring the pressure in 15 is attached. These sensors 31 to 34 are connected to the measurement apparatus main body 40, and the measurement apparatus main body 40 displays and stores the values of the characteristic parameters measured by these sensors 31 to 34.

  On the other hand, the step motor 6 for driving the throttle valve 7, the fuel injection valve 21, and the spark plug 20 are connected to the measuring device main body 40, and these step motor 6 and the like are driven and controlled by the measuring device main body 40. That is, the value of the control parameter is changed by the measuring device body 40.

  For example, considering the case of obtaining MBT in various control states by adapting work, first, at a plurality of measurement points in which only the ignition timing is changed in a certain control state, characteristic parameters such as torque, misfire, etc. Measure. Based on the measured values such as torque and misfire, the MBT in the engine operating state is obtained. Then, after the control state is changed slightly, for example, only the air-fuel ratio is changed slightly, and then the MBT in the control state is obtained again by the above method. Such work is performed for all control states (hereinafter simply referred to as “all control states”) that are assumed to be actually operated. In this way, MBT in all control states is obtained. However, if the characteristic parameter values are measured in all control states in this way, the number of measurement points becomes very large.

  Further, in general, in the calibration work, the measurement of the characteristic parameter value at a certain measurement point is performed after a certain amount of time has elapsed after the control parameter is changed, and most of the characteristic parameter values are stabilized. This is because if the measurement is performed before the value of the characteristic parameter is stabilized, the accurate value of the characteristic parameter may not be measured when steady operation is performed in the control state. Thus, by performing measurement after the value of the characteristic parameter is stabilized, it is possible to accurately measure the value of the characteristic parameter during steady operation in the control state. However, when the measurement is performed after waiting for the characteristic parameter value to stabilize for each control state in this way, the number of measurement steps becomes enormous, considering that the number of measurement points is very large as described above. End up.

  Therefore, in this embodiment, the value of the characteristic parameter is measured for each cylinder in a state where the value of at least one control parameter is different among the cylinders. Hereinafter, a case will be described in which the ignition timing is used as the control parameter and the characteristic parameter value is measured for each cylinder in a state where the ignition timing is different for each cylinder.

  FIG. 3 shows measured values of torque and exhaust temperature when the ignition timing is different for each cylinder. In the illustrated example, the ignition timings of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder are 6 °, 28 °, 15 °, and 22 ° (BTDC) before compression top dead center of each cylinder, respectively. Accordingly, the degree of advance is in the order of # 2, # 4, # 3, # 1 from the larger to the smaller.

  In measuring torque and the like, control parameters other than the ignition timing, for example, the air-fuel ratio, the operating angle or the phase angle of the intake valve 17 or the exhaust valve 19 are set to the same value. On the other hand, the engine speed and the like cannot be different among the cylinders, and are therefore the same for all the cylinders. Thus, in this embodiment, in one measurement, the control state excluding the ignition timing is the same for all the cylinders, and only the ignition timing is different among the cylinders. Furthermore, the measurement of the characteristic parameter value is performed after a certain amount of time has elapsed since the start of the operation in the control state, that is, after the engine operation state is stabilized.

  As described above, as a result of setting the ignition timing to be different for each cylinder, the measured value of the torque generated by the combustion in each cylinder is different for each cylinder. In the illustrated example, the torque generated by the combustion in the first cylinder is the smallest and increases in the order of the third cylinder, the fourth cylinder, and the second cylinder. The torque of each cylinder measured in this way is considered to be substantially equal to the torque of the internal combustion engine when ignition is performed in all cylinders at the same ignition timing as that of the cylinder. For example, the torque measured in the first cylinder is approximately equal to the torque generated by the internal combustion engine when steady operation is performed with the ignition timing set to 6 ° before compression top dead center for all cylinders. Conceivable.

  Therefore, according to the present embodiment, which is a four-cylinder internal combustion engine, the torque when ignition is performed at four different ignition timings can be measured by one measurement. In particular, in the present embodiment, it is possible to measure the torque generated by the internal combustion engine when steady operation is performed with the ignition timing being 6 °, 15 °, 22 °, and 28 ° before compression top dead center. For this reason, torque can be measured at four measurement points by one measurement, and the number of measurement steps can be greatly reduced.

  The normal torque is measured by detecting torque generated on a crankshaft (not shown) of the internal combustion engine with a torque sensor. However, when torque is measured by such a method, torque generated by combustion in all cylinders can be measured, but torque generated by combustion cannot be measured for each cylinder. Therefore, in this embodiment, a cylinder pressure sensor (not shown) for measuring the pressure in the combustion chamber 15 is provided for each cylinder, and combustion is performed for each cylinder based on the cylinder pressure detected by the cylinder pressure sensor. The torque generated by is to be measured.

  Similarly, in the present embodiment, the temperature of the exhaust gas discharged from the combustion chamber 15 for each cylinder is measured by the exhaust temperature sensor 33, and the measured values of the exhaust temperature are different values for each cylinder. Yes. In the example shown in FIG. 3, the exhaust temperature of the exhaust gas discharged from the second cylinder is the lowest, and increases in the order of the fourth cylinder, the third cylinder, and the first cylinder. The exhaust temperature of the exhaust gas discharged from each cylinder thus measured is substantially equal to the exhaust temperature when all the cylinders are ignited at the same ignition timing as that of the cylinder. it is conceivable that. Therefore, as in the case of the torque described above, according to the present embodiment, which is a four-cylinder internal combustion engine, the exhaust temperature when ignition is performed at four different ignition timings can be measured by one measurement. The measurement man-hours can be greatly reduced.

  From the torque and exhaust temperature when ignition is performed at each ignition timing thus measured, as shown in FIG. 4, the relationship between the ignition timing and the torque in the control state and the ignition timing and the exhaust temperature. A relationship can be sought. That is, according to this embodiment, the relationship between the ignition timing, torque, and exhaust temperature in a certain control state can be obtained by a single measurement.

  Of course, in addition to one measurement in each control state, a plurality of measurements may be performed, and the relationship between the ignition timing, torque, and exhaust temperature in a certain control state may be obtained as a result of the plurality of measurements. In this case, in the present embodiment, which is intended for a four-cylinder internal combustion engine, torque and exhaust temperature can be measured at eight measurement points in the control state by performing measurement twice in a certain control state. By performing the measurement once, the torque and the exhaust temperature can be measured at 12 measurement points in the control state.

  In the above-described embodiment, the case where the ignition timing is different for each cylinder has been described. However, the control parameters having different values for each cylinder are the phase angle or working angle of the intake valve 17 and the phase of the exhaust valve 19. The angle or working angle, fuel injection amount, or air-fuel ratio may be used. In addition to the torque and exhaust temperature described above, the measured characteristic parameters include air-fuel ratio, exhaust emission, and the like.

  Next, a second embodiment of the present invention will be described. Since there are usually some manufacturing errors in the shape of each cylinder of the internal combustion engine, the shape of the intake valve 17 or the exhaust valve 19, the fuel injection valve 21, the intake valve drive device 22 and the exhaust valve drive device 23, as described above. Even when the control parameters are not different among the cylinders and the control state is the same for all the cylinders, the measured characteristic parameter values may have some errors between the cylinders. .

  Further, for example, in a four-cylinder internal combustion engine, the first cylinder and the fourth cylinder are located at the end of the cylinder row. For this reason, the 2nd and 3rd cylinders are affected by the temperature of the adjacent cylinders, whereas the 1st and 4th cylinders are only affected by the temperature of one adjacent cylinder. Therefore, even when the control state is the same for the first and fourth cylinders located at the end of the cylinder row and the second and third cylinders located in the middle of the cylinder row, the characteristic parameter An error is likely to occur in the value (particularly the value of the characteristic parameter related to temperature).

  Thus, even when the control state is the same, the measured characteristic parameter value may vary between cylinders. When the control parameter value is measured with different values between the cylinders in a state where there is such a variation between the cylinders, the value of the measured characteristic parameter for each cylinder becomes a value including the variation. For this reason, if there is variation between the cylinders, an error is likely to occur in the measured value of the characteristic parameter, and the value of the characteristic parameter when the steady operation is performed with the value of each control parameter cannot be obtained accurately.

  Therefore, according to the present embodiment, apart from the measurement of the characteristic parameter value performed with different control parameter values among the cylinders, the control parameter values are assumed to be equal for all cylinders, that is, control is performed for all cylinders. The value of the characteristic parameter is measured for each cylinder with the same state. When there is variation among the cylinders in the characteristic parameter values measured with the same control state for all cylinders, the characteristic parameter values measured with different control parameter values between the cylinders as described above Is corrected based on the variation between the cylinders.

  As an example, a case where the ignition timing is adjusted as a control parameter and the exhaust temperature is measured as a characteristic parameter will be described. First, the exhaust temperature is measured for each cylinder with the same ignition timing for all cylinders. If the measured exhaust temperature differs between cylinders, calculate the average exhaust temperature for all cylinders, and make an error with the average exhaust temperature for all cylinders or the exhaust temperature for all cylinders. The ratio of the exhaust temperature of each cylinder to the average value is calculated. And by measuring the exhaust temperature etc. with different ignition timing for each cylinder, adding or subtracting the error to the measured exhaust temperature, or multiplying the measured exhaust temperature by the ratio, Correct the measured exhaust temperature. The exhaust temperature thus corrected is acquired as the exhaust temperature when the steady operation is performed at each ignition timing.

  A case will be described in which ignition timing is adjusted as a control parameter and torque is measured as a characteristic parameter. In this case, the torque is measured for each cylinder with the same ignition timing for all the cylinders. At this time, the relationship between the in-cylinder pressure of each cylinder measured by the in-cylinder pressure sensor and the torque by the engine body 1 measured by the torque sensor is obtained for each cylinder. Then, the torque is measured with different ignition timings for each cylinder, that is, the in-cylinder pressure of each cylinder is measured, and the measured in-cylinder pressure of each cylinder is based on the relationship between the in-cylinder pressure and the torque for each cylinder. to correct. The torque thus corrected is acquired as the torque when the steady operation is performed at each ignition timing.

  In this way, by correcting the measured characteristic parameter value according to the variation between the cylinders, even if there is a variation between the cylinders, the measured characteristic parameter value is less susceptible to the influence. It becomes possible to reduce the error of the value.

  By the way, when the phase angles of the intake valve 17 and the exhaust valve 19 are different between the cylinders, when there is a state where both the intake valve 17 and the exhaust valve 19 are open, that is, when there is a valve overlap, The in-cylinder charged air amount and torque fluctuate due to the influence of exhaust pulsation generated in the exhaust port 18, the exhaust manifold 8 and the exhaust pipe 9 (hereinafter referred to as “exhaust passage”). However, according to the above embodiment, since the control state is different for each cylinder, the influence of a certain cylinder due to exhaust pulsation is that when other cylinders are also operated in the same control state. There is a case where the influence of the certain cylinder due to the exhaust pulsation is different. As a result, the measured value of the characteristic parameter (for example, torque) is different from the value of the characteristic parameter measured when the control state for all the cylinders is the same as the control parameter value for that cylinder.

  Therefore, according to the present embodiment, a pressure sensor for measuring the pressure in the exhaust pipe is provided to measure the exhaust pulsation generated in the exhaust passage corresponding to each cylinder, and the characteristic parameter based on the measured exhaust pulsation The measured value is corrected. Thereby, the value of the characteristic parameter measured when the control state in all the cylinders is the same can be obtained from the measured value of the characteristic parameter.

It is a figure which shows the measuring device used for the internal combustion engine used as an object of adaptation work, and adaptation work. It is a schematic sectional drawing of each cylinder. It is a figure which shows the measured value of a torque and exhaust temperature when the ignition timing is made different for each cylinder. It is a figure which shows the relationship between the ignition timing calculated | required based on the measured value of FIG. 3, torque, and exhaust temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 7 Throttle valve 17 Intake valve 19 Exhaust valve 20 Spark plug 21 Fuel injection valve 31 Throttle opening sensor 32 Air flow meter 33 Exhaust temperature sensor 34 Air-fuel ratio sensor 40 Measuring device body

Claims (2)

A method for measuring a characteristic parameter of an internal combustion engine, in which the value of the control parameter is set to various values and the value of the characteristic parameter is measured for each value of the control parameter when steady operation is performed with the value of the control parameter. In
A method for measuring a characteristic parameter of an internal combustion engine, wherein the value of the characteristic parameter is measured for each cylinder in a state in which the value of at least one control parameter is different among the cylinders.   When the value of the characteristic parameter is measured for each cylinder in the state where the value of the control parameter is the same for all the cylinders, and the characteristic parameter value measured in such a state has a variation among the cylinders, 2. The internal combustion engine according to claim 1, wherein the value of the characteristic parameter for each cylinder measured in a state where the value of at least one control parameter is different among the cylinders is corrected based on the variation between the cylinders. Characteristic parameter measurement method.

Images