JP2011247107A - Control method for multi-cylinder internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To alleviate or eliminate a problem of deterioration in emission and fuel consumption in an internal combustion engine in which explosion occurs at irregular intervals.SOLUTION: A control method for a multi-cylinder internal combustion engine calculates a fuel injection time for each cylinder on the basis of pressure in an air-intake pipe measured at each cylinder. When calculating the fuel injection time at each cylinder, the pressure in the air-intake pipe at a prescribed crank angle is measured at each cylinder. A correction amount is determined on the basis of the actual measurement value in the immediately-previous air-intake stroke of the cylinder and the actual measurement value in the air-intake stroke of the other cylinder. The fuel injection time of the cylinder is calculated on the basis of the predicted value of the pressure in the air-intake pipe obtained by adding the correction amount to the actual measurement value of the pressure in the air-intake pipe in the immediately-previous air-intake stroke of the cylinder.

Description

  The present invention relates to a control method for a multi-cylinder internal combustion engine having a plurality of cylinders.

  Recently, attempts have been made to reduce the number of cylinders in order to further improve fuel efficiency in an onboard internal combustion engine.

  In a two-cylinder internal combustion engine, a problem that low-frequency rigid body vibration occurs and is recognized as in-vehicle noise becomes obvious. Although it is known to provide a balance shaft as one of means for suppressing rigid body vibration of an internal combustion engine, the use of such a balance shaft increases the number of parts and makes it difficult to reduce costs. In view of this, it has been considered that an internal combustion engine with unequal interval explosions in which the expansion strokes of the cylinders come at unequal intervals is used to suppress vibrations regardless of the balance shaft (see, for example, Patent Document 1).

  If an internal combustion engine that performs non-uniform explosions is controlled in the same manner as an internal combustion engine that performs equidistant explosions, emissions and fuel consumption may deteriorate.

  As a result of various investigations by the inventors to solve such problems, the following has been found. That is, because the estimation of the pressure in the intake pipe during the intake stroke of each cylinder is incorrect, the fuel injection time to be injected into the cylinder is not appropriate, and as a result, harmful substances in the exhaust gas increase, and / Or the fuel economy was getting worse.

  This problem can occur not only in a two-cylinder internal combustion engine but also in a multi-cylinder internal combustion engine having three or more cylinders.

JP 2005-133568 A

  An object of the present invention is to alleviate or eliminate the problems of deterioration of emission and fuel consumption in an internal combustion engine with unequal interval explosions.

  The present invention was made based on the above-described investigation results, and in a control method for a multi-cylinder internal combustion engine that calculates a fuel injection time for each cylinder based on an intake pipe pressure measured for each cylinder. When calculating the fuel injection time for each cylinder, the pressure in the intake pipe at a predetermined crank angle is measured for each cylinder, and based on the measured value in the intake stroke immediately before the cylinder and the measured value in the intake stroke of other cylinders. The correction amount is determined, and the fuel injection time of the cylinder is calculated based on the estimated value of the intake pipe pressure obtained by adding the correction amount to the actual value of the intake pipe pressure in the intake stroke immediately before the cylinder. It was decided.

  As a specific aspect, in the control method for a multi-cylinder internal combustion engine that calculates the current fuel injection time of each cylinder based on the intake pipe pressure at a predetermined crank angle of the previous intake stroke of each cylinder, When calculating the current fuel injection time, the measured value of the intake pipe pressure at a predetermined crank angle of the previous intake stroke of the cylinder and the intake air between the previous intake stroke and the current intake stroke of the specific cylinder The correction amount is determined based on the difference between the measured value of the intake pipe pressure at the predetermined crank angle of the intake stroke of the other cylinders that have reached the stroke, and the measured value of the intake pipe pressure during the previous intake stroke of the cylinder is determined. There is one that calculates the fuel injection time based on the estimated value of the intake pipe pressure obtained by taking the correction amount into consideration.

  According to the present invention, it is possible to alleviate or eliminate the problems of deterioration of emission and deterioration of fuel consumption in an internal combustion engine with unequal interval explosions.

The figure which shows the outline | summary of the internal combustion engine for vehicles used as the application object of this invention. The figure explaining the stroke of each cylinder of the internal combustion engine. The figure which shows the hardware resource structure of the control part which manages control of the internal combustion engine. The figure which shows the mode of the change of the intake pipe internal pressure of the internal combustion engine roughly. The figure which shows the mode of the change of the intake pipe internal pressure of the internal combustion engine roughly. The flowchart which shows the procedure of the process which a control part performs.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine 0 to which the control method of this embodiment is applied. The internal combustion engine 0 in the present embodiment is a two-cylinder gasoline engine, and FIG. 1 shows a schematic configuration of an arbitrary one of the two cylinders.

  The internal combustion engine 0 includes each cylinder 1, an injector 2 for injecting fuel, an intake system path 3 for supplying intake air to each cylinder 1, and an exhaust system path 4 for exhausting exhaust from each cylinder 1. It comprises.

  The intake system path 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a throttle valve 32, and a surge tank 33 are arranged in this order from the upstream side. Further, there is a bypass passage 34 that bypasses the throttle valve 32, and an idle speed control valve 35 is provided in the bypass passage 34.

  The exhaust system path 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. A three-way catalyst 41 is disposed on the exhaust system path 4.

  In a normal two-cylinder internal combustion engine, the expansion stroke of the first cylinder and the expansion stroke of the second cylinder come at equal intervals with a phase difference of 360 ° CA (crank angle), and the piston of the first cylinder and the second cylinder The piston moves forward and backward in perfect synchronization. Therefore, the vibration of the internal combustion engine itself tends to increase, and it is a common practice to use a balance shaft to suppress the vibration.

  However, in this embodiment, in order to reduce the cost by eliminating the balance shaft, the first cylinder and the second cylinder perform an unequally spaced explosion in which the expansion strokes come at uneven intervals. The piston advance / retreat operation and the piston advance / retreat operation of the second cylinder are made asynchronous. In the internal combustion engine 0, the protruding direction of the crank arm connected to the piston of the first cylinder and the protruding direction of the crank arm connected to the piston of the second cylinder intersect substantially perpendicularly. Thereby, as shown in FIG. 2, the phase difference between the expansion stroke of the first cylinder and the expansion stroke of the second cylinder is 270 ° CA.

  The ECU 9 as a control unit that controls the internal combustion engine 0 is a microcomputer system having a processor 91, a memory 92, an input interface 93, an output interface 94, and the like as shown in FIG.

As shown in FIGS. 1 and 3, the input interface 93 includes an intake pressure signal a output from the intake pressure sensor 11 for detecting the pressure in the surge tank 33, that is, the intake pipe pressure PM, and the intake temperature sensor 12. Detects the output intake air temperature signal b, the water temperature signal c output from the water temperature sensor 13 for detecting the cooling water temperature of the internal combustion engine 0, the current signal d output from the O ₂ sensor 14, and the open / closed state of the throttle valve 32. A throttle opening signal e output from the throttle position sensor 15 for rotation, a rotation speed signal f output from the crank angle sensor 16 for detecting the engine rotation speed Ne, and a cam for detecting the compression top dead center of the cylinder 1 A cam angle signal g or the like output from the angle sensor 17 is input.

  The crank angle sensor 16 and the cam angle sensor 17 will be supplemented. The crank angle sensor 16 outputs the rotation speed signal f at intervals of 10 ° CA, for example. Specifically, external teeth protrude from the outer periphery of the rotating body fixed to the shaft end of the crankshaft, and an electromagnetic pickup is installed so as to face the external teeth. Are intermittently arranged at intervals of 10 ° CA. When the external teeth pass in the vicinity of the electromagnetic pickup with the rotation of the crankshaft, the electromagnetic pickup outputs a pulse signal that becomes the rotational speed signal f. The engine speed Ne can be calculated from the interval between the pulse signals. Incidentally, the crank angle sensor 16 is configured to output no signal at a predetermined timing. This is because a part of the outer teeth of the rotating body is missing. Accordingly, it is possible to detect the current rotation angle of the crankshaft with reference to the missing position.

  The cam angle sensor 17 is disposed in the vicinity of the intake camshaft, and outputs a cam angle signal g that is a pulse signal corresponding to the compression top dead center of each cylinder 1, for example. Specifically, a protrusion is provided from a rotating body fixed to the shaft end of the intake camshaft, and an electromagnetic pickup is installed so as to face the protrusion. The protrusion is electromagnetic at the timing of compression top dead center. It is arranged to pass through the vicinity of the pickup. When the projection passes near the electromagnetic pickup as the intake camshaft rotates, the electromagnetic pickup outputs a pulse signal that becomes the cam angle signal g. In the present embodiment, a pulse signal is output at the timing of the compression top dead center of the first cylinder, and then the pulse signal is output again at the timing of the compression top dead center of the second cylinder coming at an interval of 270 ° CA. . After the timing of the compression top dead center of the second cylinder, the phase difference until the timing of the compression top dead center of the first cylinder comes again is 450 ° CA.

  From the output interface 94, as shown in FIGS. 1 and 3, the fuel injection signal h for the injector 2, the ignition signal i for the ignition plug 21 (ignition coil 22 thereof), and the opening of the idle speed control valve 35. An operation signal j or the like is output.

  The processor 91 interprets and executes a program stored in advance in the memory 92 to control the operation of the internal combustion engine 0. The processor 91 acquires various information a, b, c, d, e, f, and g necessary for operation control of the internal combustion engine 0 via the input interface 93, and based on these, the fuel injection time, ignition timing, and the like are obtained. Calculate. Then, various control signals h and i corresponding to the calculation result are applied to the injector 2 and the spark plug 21 via the output interface 94.

  As one of the programs, a program for executing the control method of the internal combustion engine 0 of the present invention is stored in the memory 92. Hereinafter, an outline of the internal combustion engine control program of the present embodiment will be described with reference to FIG. Here, the intake pipe pressure PMMAX (n) [# 1] at the start of the intake stroke of the first cylinder [# 1] is predicted, and a desired empty in the first cylinder [# 1] according to the predicted value. An example of calculating the fuel injection amount TAU required to realize the fuel ratio will be described.

  First, the rotational speed Ne [# 1] immediately before the previous intake valve of the cylinder, that is, the first cylinder is opened is read (step S1). The rotational speed Ne of the internal combustion engine 0 is calculated each time based on the rotational speed signal f from the crank angle sensor 16 in the routine for calculating the engine rotational speed, and stored in the memory 92 in advance.

  Next, an actual measured value of the peak intake pipe pressure PMMAX (n−1) [# 1] immediately before the previous intake valve of the cylinder (first cylinder) is opened is read (step S2).

  Then, the actual measured value of the peak intake pipe pressure PMMAX (n−1) [# 2] immediately before the intake valve of the other cylinder, that is, the second cylinder is opened is read (step S3). In this program, the “other cylinder” is a second cylinder that has reached the intake stroke between the previous intake stroke and the current intake stroke in the specific cylinder (first cylinder).

  Based on the difference ΔPM between the peak intake pipe pressure PMMAX (n−1) [# 1] read in step S2 and the peak intake pipe pressure PMMAX (n−1) [# 2] read in step S3. The correction amount PMA of the intake pipe pressure is obtained by referring to (step S4). The difference ΔPM is a value indicating whether the intake pipe pressure PM tends to increase or decrease with respect to the steady operation state. Further, the relationship between the correction amount PMA and the difference ΔPM is obtained in advance through experiments and stored as a map.

  Next, based on the previous peak intake pipe pressure PMMAX (n-1) [# 1] and the correction amount PMA obtained in step S4, the peak intake pipe pressure PMMAX immediately before the current intake valve of the cylinder is opened. (N) An expected value corresponding to [# 1] is estimated (step S5).

Next, the fuel injection time TAU is calculated using the rotation speed Ne [# 1] read in step S1 and the predicted value corresponding to the estimated peak intake pipe pressure PMMAX (n) [# 1]. (Step S6). Regarding the calculation of the fuel injection time TAU, the basic injection amount determined by the engine speed Ne and the intake pipe pressure PM, and various correction values determined by the signals c and d from the O ₂ sensor 14 and the water temperature sensor 13 Since this is a normal operation performed by calculating the invalid injection time, the description is omitted.

  Then, the fuel injection time TAU calculated in step S6 is output to the injector 2 (step S7).

  In this way, the fuel injection time TAU of the first cylinder is sequentially determined, and fuel injection is performed. The above steps S1 to S7 are for controlling the fuel injection time TAU of the first cylinder, but the fuel injection time of the second cylinder is also calculated by the procedure according to steps S1 to S7. To do.

  In such an internal combustion engine, the intake pipe pressure PM changes as shown schematically in FIG. 4 during steady operation, but during non-steady operation, for example, as shown schematically in FIG. The previous peak intake pipe pressure PMMAX (n−1) [# 1] and the current peak intake pipe pressure PMMAX (n) [# 1] are different values. In this case, when the value of the current fuel injection time TAU is calculated using the previous peak intake pipe pressure PMMAX (n-1) [# 1] as in the prior art, it is measured immediately after fuel injection. An appropriate fuel injection time TAU cannot be obtained based on an error generated between the current peak intake pipe pressure PMMAX (n) [# 1] and the predicted value.

  However, according to the present embodiment, the predicted value corresponding to the current peak intake pipe pressure PMMAX (n) [# 1] is added to the previous peak intake pipe pressure PMMAX (n−1) [# 1] with the correction amount PMA added. Since the fuel injection time TAU is calculated using the predicted value, an appropriate fuel injection time can be obtained.

  That is, the relationship between the correction amount PMA that is obtained in advance through experiments or the like and stored as a map and the difference ΔPM has a tendency as described below for the first cylinder [# 1].

  First, during the steady operation shown in FIG. 4, the correction amount PMA corresponding to the difference ΔPM is zero.

  As an example of the non-steady operation, when the intake pipe pressure PM tends to decrease, that is, tends to change to the negative pressure side (see FIG. 5), the difference ΔPM becomes larger than that in the steady operation. The corrected amount PMA is set so that the expected value of the intake pipe pressure is smaller than the intake pipe pressure expected during steady operation.

  On the other hand, as an example at the time of unsteady operation, when the intake pipe pressure PM tends to increase, that is, tends to change to the positive pressure side (not shown), the difference ΔPM becomes smaller than that at the time of steady operation. The correction amount PMA corresponding to is set so that the expected value of the intake pipe pressure is larger than the expected intake pipe pressure during steady operation.

  Similarly, for the second cylinder [# 2], the predicted value corresponding to the current peak intake pipe pressure PMMAX (n) [# 2] is set to the previous peak intake pipe pressure PMMAX (n−1) [# 2 ], Taking the correction amount PMA into consideration, and calculating the fuel injection time TAU using the predicted value, an appropriate fuel injection time can be obtained.

  That is, the relationship between the correction amount PMA, which is obtained in advance through experiments or the like and stored as a map, and the difference ΔPM corresponds to the first cylinder [# 1] described above. The details are as follows.

  As an example of the non-steady operation, when the intake pipe pressure PM tends to decrease, that is, tends to change to the negative pressure side (see FIG. 5), the difference ΔPM is smaller than that in the steady operation, and thus corresponds to ΔPM. The corrected amount PMA is set so that the expected value of the intake pipe pressure is smaller than the intake pipe pressure expected during steady operation.

  On the other hand, as an example of the unsteady operation, when the intake pipe pressure PM tends to increase, that is, tends to change to the positive pressure side (not shown), the difference ΔPM becomes larger than that during the steady operation. The correction amount PMA corresponding to is set so that the expected value of the intake pipe pressure is larger than the expected intake pipe pressure during steady operation.

  The same effect can be obtained in the second cylinder. Therefore, even in the internal combustion engine 0 that performs non-uniform explosions in which the expansion strokes of the first cylinder and the second cylinder come at unequal intervals, it is possible to effectively suppress or prevent the deterioration of emission and fuel consumption.

  Although the embodiment of the present invention has been described above, the specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  In FIG. 5, as an example of the change in the intake pipe pressure during the unsteady operation, the change in the intake pipe pressure in the negative pressure direction with the change in the crank angle is shown. Problems similar to those shown in FIG. Therefore, if the control method for an internal combustion engine of the present invention is used, it is possible to effectively suppress or prevent the deterioration of emission and / or the deterioration of fuel consumption.

  In order to calculate the fuel injection time in step S6 of the present embodiment, the rotation speed immediately before the previous intake valve of the first cylinder is opened is used, but immediately before the intake valve of the second cylinder, which is another cylinder, is opened. May be used.

  In the above-described embodiment, the engine speed used for determining the combustion injection time is an actually measured value of the engine speed immediately before the previous intake valve is opened, but is not limited thereto. That is, as the engine speed of the present invention, an actual measured value of the engine speed at a predetermined crank angle of the intake stroke other than immediately before the intake valve is opened may be used. A value obtained by predicting the engine speed immediately before opening may be used.

  Further, the correction amount of the intake pipe pressure is not limited to that obtained from the map, but may be calculated every time the program is executed.

  Furthermore, in the above embodiment, the present invention is applied to a two-cylinder internal combustion engine. However, the present invention is of course not limited to a two-cylinder internal combustion engine, and may be applied to a three-cylinder or more multi-cylinder internal combustion engine. good. In this case, the present invention may be applied to all the cylinders of the multi-cylinder internal combustion engine or may be applied to some of the plurality of cylinders. Further, for example, in the case of three cylinders, the “other cylinder” of the present invention is the first cylinder that has reached the intake stroke between the previous intake stroke and the current intake stroke in the specific cylinder (first cylinder). Either two cylinders or a third cylinder may be used.

  Further, the present invention can be applied to various types of engines, regardless of whether they are V-type or series-type.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

0 ... Internal combustion engine 1 ... Cylinder TAU ... Fuel injection time PM ... Intake pipe pressure PMA ... Correction amount

Claims (1)

In a control method of a multi-cylinder internal combustion engine that calculates a fuel injection time for each cylinder based on an intake pipe pressure measured for each cylinder,
When calculating the fuel injection time for each cylinder, the pressure in the intake pipe at a predetermined crank angle is measured for each cylinder, and based on the measured value in the intake stroke immediately before the cylinder and the measured value in the intake stroke of other cylinders. The correction amount is determined, and the fuel injection time of the cylinder is calculated based on the estimated value of the intake pipe pressure obtained by adding the correction amount to the actual value of the intake pipe pressure in the intake stroke immediately before the cylinder. A control method for a multi-cylinder internal combustion engine.

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