JP4359890B2 - 4-stroke engine fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device for a four-stroke engine that switches fuel injection control modes before and after stroke determination.

  The 4-stroke engine is an engine in which one cycle of operation is completed by four strokes of an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. In a 4-stroke engine, the cycle is completed by rotating the output shaft twice. For this reason, depending on the rotation angle within one rotation of the output shaft, it is not possible to perform a so-called stroke determination for determining which stroke is in the stroke. If the stroke cannot be determined, the timing for performing the fuel injection control cannot be grasped, and the engine operation cannot be accurately controlled.

  For this reason, in the 4-stroke engine, for example, the stroke is determined based on the rotation angle of the camshaft that rotates twice while the output shaft rotates once. When the stroke is determined, the timing of fuel injection control, the timing of ignition timing control, and the like can be accurately grasped. However, since the stroke determination is performed based on the rotation of the camshaft, the stroke determination is not yet completed immediately after the start of the rotation of the camshaft.

  Therefore, conventionally, as seen in Patent Document 1, for example, in a multi-cylinder engine, a fuel injection control device has been proposed in which fuel injection is simultaneously performed on all cylinders before stroke determination. That is, as illustrated in FIG. 7 for a four-cylinder engine, fuel injection is simultaneously performed four times for all cylinders during one cycle before stroke determination. As a result, even before the stroke is determined, the required amount of fuel is supplied to the combustion chamber of the engine during the intake stroke. Furthermore, in the fuel injection control device described in Patent Document 1, it has also been proposed to reduce the fuel injection amount for the first “N−1” times after the stroke determination in the N-cylinder engine from the required injection amount. ing. That is, as shown in FIG. 7, in the four-cylinder engine, the fuel injection amount of “4-1” times after the stroke determination is corrected to decrease. For this reason, in the first three cylinders that perform fuel injection after stroke determination, the fuel injection amounts are respectively “γ1 × TAU, γ2 × TAU, γ3 × TAU (TAU is the required fuel amount: γ1 <γ2 <γ3 < 1) "is corrected for reduction. Thereby, it is possible to avoid an excessive amount of fuel being used for combustion in the combustion stroke after the stroke determination.

  By the way, simultaneous injection is not necessarily desirable before stroke determination. For example, when fuel is injected near the exhaust top dead center, the top dead center including both the exhaust top dead center and the compression top dead center can be specified by the output shaft even before the stroke determination. it can. For this reason, fuel injection can be performed every time the top dead center is reached before the stroke is determined. However, in the case of injecting fuel before reaching the top dead center before the stroke determination, the fuel injection control device of the above patent publication may not be able to properly perform the fuel injection after the stroke determination. .

  For example, as shown in FIG. 8, in a two-cylinder engine, when the first fuel injection is performed after stroke determination, if the injection amount is reduced to “α × TAU (α <1)”, an appropriate fuel injection amount is not obtained. . This is because the fuel injected into the second cylinder before the stroke determination is supplied to the combustion chamber in the intake stroke before the stroke determination, and then used for combustion.

In addition to the example of FIG. 8, when the stroke is determined, in a fuel injection control device of a 4-stroke engine that switches from fuel injection once every two strokes to fuel injection once every four strokes, etc. Such a situation in which it is difficult to appropriately control the fuel injection amount after the stroke determination is generally common.
JP 9-242594 A

  The problem to be solved by the present invention is a fuel injection control device for a four-stroke engine that switches the fuel injection control mode before and after the stroke determination, and it is difficult to appropriately control the fuel injection amount after the stroke determination. is there.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  In means 1, when the stroke determination, which is the determination of which of the four strokes is one cycle of four strokes, is completed, the fuel injection is switched from one fuel injection every two strokes to one fuel injection every four strokes. In the fuel injection control device for a stroke engine, the fuel injection once every two strokes is performed in a stroke in which the fuel is injected once in the four strokes and a stroke separated by “360 ° CA” from the stroke. Means for determining whether or not the fuel injected immediately before completion of the stroke determination has been used for combustion, and when determined not to be used for combustion, And means for reducing the initial fuel injection amount.

  Before the stroke is determined, it is not possible to uniquely specify the timing at which fuel injection is performed once every four strokes depending on the rotation angle within one rotation of the output shaft of the engine. However, it is possible to simultaneously specify two strokes: a stroke in which fuel is injected in one fuel injection every four strokes and a stroke separated by “360 ° CA” from the stroke, depending on the rotation angle within one rotation of the output shaft. . If the fuel injection control is performed in such a manner, the angle region within one rotation for performing the fuel injection can be shared before and after the stroke determination. For this reason, in the said structure, the fuel-injection time before stroke determination can be easily set in the angle area | region within one rotation of an output shaft.

  Further, by determining whether or not the fuel injected just before the stroke determination has been made has been used for combustion, if it is being used for fuel, it is appropriate without reducing the fuel injection amount after the stroke determination. A large amount of fuel can be injected. Here, “the fuel injected immediately before has been used for combustion” means that the fuel injected immediately after the stroke determination in the combustion stroke before the combustion stroke in which the fuel injected after the stroke determination is subjected to combustion Is defined as subject to combustion.

  In the means 2, in the means 1, the engine is a multi-cylinder engine, and the means for determining determines, for each cylinder, whether or not the fuel injected immediately before the stroke determination is performed is used for combustion. The means for decreasing the amount is configured to decrease the initial fuel injection amount after the stroke determination for each of the cylinders when it is determined that it is not used for the combustion.

  Thereby, in each cylinder, the amount of fuel provided for combustion in the combustion stroke immediately after the stroke determination can be made appropriate.

  Even when the means 1 is applied to a multi-cylinder engine, it is possible to appropriately control the initial fuel injection amount after the stroke determination. However, it is particularly desirable that the means 1 is applied to a single cylinder engine.

  In the means 3, in the means 1 or 2, the means for judging is based on whether or not the fuel injection immediately before the stroke determination is made in the stroke in which the injection is performed once in the four strokes. Judgment was made on whether or not it was served.

  Immediately before the stroke determination is made, when fuel injection is performed in a stroke in which fuel is injected once every four strokes, the injected fuel is used for combustion by the fuel injected after the stroke determination. It will be used for combustion in the combustion stroke before the combustion stroke. For this reason, in the said structure, the judgment whether it was used for combustion can be performed appropriately.

  Note that any one of the means 1 to 3 further includes means for calculating the fuel injection amount based on at least one of the operating state and the operating environment of the engine, as in the means 4, and reducing the initial fuel injection amount. May be performed by reducing the fuel injection amount calculated as described above.

  In the means 5, the fuel injection amount in the fuel injection twice in the four strokes in the means 4 is set to substantially “½” of the calculated fuel injection amount.

  According to the above configuration, an appropriate amount of fuel is used for combustion even in the combustion stroke before the stroke determination, and the engine startability can be improved.

  In the means 6, in the means 4 or 5, the fuel injection amount reduction correction is a correction that makes the calculated fuel injection amount substantially "1/2".

  In the above configuration, the amount of reduction correction when the amount of reduction correction is performed after the stroke determination can be determined easily and appropriately.

  Hereinafter, an embodiment in which a fuel injection control device for a four-stroke engine according to the present invention is applied to a fuel injection control device for a two-cylinder engine will be described with reference to the drawings.

  FIG. 1 shows the configuration of a fuel injection control device of this embodiment and a two-cylinder engine that is a control target thereof.

  As shown, the engine 1 includes two cylinders, a first cylinder 2a and a second cylinder 2b. An intake passage 4a and an intake passage 4b are connected to the first cylinder 2a and the second cylinder 2b, respectively. Intake passages 4a and 4b are provided with injectors 6a and 6b for supplying fuel to the intake passages 4a and 4b, respectively. The intake passages 4a and 4b are provided with throttle valves 8a and 8b for adjusting the flow passage areas, respectively, and further, the upstream side thereof is connected to the air cleaner 10. In this way, the engine 1 is a so-called independent intake engine in which the intake passages 4a and 4b are provided independently of each other without being gathered and the flow passage areas of the intake passages 4a and 4b are individually adjusted. Yes.

  On the other hand, the electronic control unit 20 includes a central processing unit and a memory, and controls the operation state of the engine 1. Specifically, the detection results of various sensors that detect the operating state and operating environment of the engine 1 are taken in, and the operating state of the engine 1 is controlled based on this. Examples of these various sensors include an intake pressure sensor 30 that detects the pressure in the intake passage 4a and a crank angle sensor 34 that detects the rotation angle of the output shaft (crankshaft 32) of the engine 1.

  Here, the crankshaft 32 is provided with a signal rotor 36 having unevenness that is repeated at a predetermined interval (for example, “15 ° CA”) and a missing tooth portion in which the unevenness is irregularly missing. The crank angle sensor 34 detects the rotation angle of the crankshaft 32 based on the unevenness and chipped portions of the signal rotor 36. That is, the reference angle of the crankshaft 32 is detected based on the missing tooth portion of the signal rotor 36 (reference position discrimination), and every time the convex portion is detected with reference to this, the fact that the crankshaft 32 is rotated by the predetermined interval is detected. To detect.

  However, only the crank angle sensor 34 cannot determine which stroke each of the first cylinder 2a and the second cylinder 2b is in. For this reason, in this embodiment, the stroke determination is performed using the detection value of the intake pressure sensor 30. FIG. 2 shows the transition of the intake pressure of a specific cylinder. As shown in the figure, the intake pressure of the specific cylinder decreases as the intake stroke starts, and increases after the intake stroke ends. Therefore, when the detection value of the intake pressure sensor 30 decreases, it can be determined that the first cylinder 2a is in the intake stroke, and the stroke determination of the first cylinder can be performed. Further, since the cycle of the second cylinder 2b has a predetermined relationship with the cycle of the first cylinder 2a, the stroke determination of the second cylinder 2b can be performed based on the stroke determination of the first cylinder 2a.

  Next, fuel injection control according to the present embodiment will be described.

  In the present embodiment, the fuel injection amount required according to the operating state of the engine 1 is calculated, and fuel injection is basically performed based on this. However, fuel injection control may be performed after correcting the required fuel injection amount before and after the stroke determination.

  Here, a process for calculating the required fuel injection amount will be described first. FIG. 3 shows a processing procedure for calculating the required fuel injection amount. This process is repeatedly executed by the electronic control unit 20 at a predetermined cycle, for example.

  In this series of processing, first, in step S1, detection values of the operating state of the engine 1, such as detection values of the intake pressure sensor 30 and detection values of the crank angle sensor 34, are captured. Here, the detected value of the intake pressure sensor 30 is a parameter for grasping the load of the engine 1, and the detected value of the crank angle sensor 34 is a parameter for grasping the rotational speed of the crankshaft 32. In the subsequent step S2, the required fuel injection amount (required injection amount TAU) is calculated based on the detection value captured in step S1.

  Next, fuel injection control according to the present embodiment will be described. FIG. 4 shows a processing procedure for fuel injection control. This process is performed independently for each cylinder, in other words, for each of the first cylinder 2a and the second cylinder 2b.

  In this series of processes, when it is determined that the reference position determination has not been completed (step S11, NO), the fuel injection control is not performed. On the other hand, when the reference position determination is completed and the stroke determination is not completed (step S12, NO), fuel injection control is performed once every two strokes based on the rotation angle of the crankshaft 32. Here, the timing of fuel injection is a stroke in which the fuel is injected once every four strokes, and a stroke separated by “360 ° CA” from the stroke. In other words, they are near the exhaust top dead center (exhaust stroke and intake stroke) and near the compression top dead center (compression stroke and combustion stroke) for each of the first cylinder 2a and the second cylinder 2b. For this reason, fuel injection is performed every “360 ° CA”. The fuel injection amount is set to “½” of the required fuel injection amount TAU calculated in the process shown in FIG.

  When the stroke determination is completed (step S12, YES), fuel injection control is performed once every four strokes, in other words, every “720 ° CA”. Here, the stroke in which the injection is performed is in the vicinity of the exhaust top dead center for each of the first cylinder 2a and the second cylinder 2b. Here, basically, the fuel of the required injection amount TAU calculated in the process shown in FIG. 3 is injected (step S14, NO and step S15). However, at this time, in the first fuel injection after the stroke determination (step S14, YES), the fuel injection control mode is changed according to the determination in step S16.

  That is, when the fuel injection is the first time and the previous injection stroke (the injection stroke immediately before the stroke determination) is in the vicinity of the compression top dead center (back) (step S16, NO), the required injection amount TAU “ 1/2 "of fuel is injected (step S17). On the other hand, when it is the first fuel injection and the previous injection stroke is in the vicinity of the exhaust top dead center (table) (step S16, YES), the fuel of the required injection amount TAU is injected (step S15). . In this way, in step S16, for each of the first cylinder 2a and the second cylinder 2b, it is determined whether or not the fuel injected immediately before the stroke determination has been used for combustion. The injection amount is set.

  Here, the effect of the fuel injection control according to the present embodiment will be described with reference to FIGS.

  First, FIG. 5 shows a case where the fuel injection immediately before the stroke determination is made at the compression top dead center.

  5A shows the transition of each cycle of the first cylinder 2a and the second cylinder 2b, FIG. 5B shows the transition of the output of the crank angle sensor 34, and FIG. 5C shows the intake passage 4a. , 4b, FIG. 5 (d) shows the transition of the fuel injection timing and injection amount of the first cylinder 2a, and FIG. 5 (e) shows the fuel injection timing and injection amount of the second cylinder 2b. Each transition is shown.

  As shown in the drawing, before the stroke determination is made, fuel of “½” of the required injection amount TAU is injected, so that the required injection is performed in each intake stroke of the first cylinder 2a and the second cylinder 2b. An amount of TAU fuel is taken into the combustion chamber and used for combustion in the combustion stroke.

  On the other hand, in the first fuel injection after the stroke determination, “1/2” of the required fuel amount TAU is injected. Thereby, in the first intake stroke after the stroke determination, the fuel amount “TAU / 2” injected last before the stroke determination and the fuel amount “TAU / 2” injected first after the stroke determination are stored in the combustion chamber. Will be captured. For this reason, the fuel of the required injection amount TAU is used for combustion also in the first combustion stroke after the stroke determination.

  On the other hand, when the initial fuel injection amount is the required injection amount TAU after the stroke determination, the fuel injection timings and injections of the first cylinder 2a and the second cylinder 2b are shown in FIGS. 5 (f) and 5 (g). As shown in the transition of the amount, in the first intake stroke after the stroke determination, the fuel amount “TAU / 2” injected last before the stroke determination and the required injection amount which is the first fuel amount injected after the stroke determination TAU is taken into the combustion chamber. For this reason, the amount of fuel used for combustion becomes excessive in the first combustion stroke after the stroke determination.

  On the other hand, FIG. 6 shows a case where the fuel injection immediately before the stroke determination is performed near the exhaust top dead center.

  6A shows the transition of each cycle of the first cylinder 2a and the second cylinder 2b, FIG. 6B shows the transition of the output of the crank angle sensor 34, and FIG. 6C shows the intake passage 4a. , 4b, FIG. 6 (d) shows the transition of the fuel injection timing and the injection amount of the first cylinder 2a, and FIG. 6 (e) shows the fuel injection timing and the injection amount of the second cylinder 2b. Each transition is shown.

  As shown in the figure, in this case, the fuel of the required fuel amount TAU is injected at the first fuel injection after the stroke determination. Thereby, in the first intake stroke after the stroke determination, the fuel of the required injection amount TAU injected after the stroke determination is taken into the combustion chamber. For this reason, the fuel of the required injection amount TAU is used for combustion also in the first combustion stroke after the stroke determination. That is, in this case, since the fuel injected in the fuel injection immediately before the stroke determination is taken into the combustion chamber in the intake stroke before the stroke determination, it has already been used for combustion at the time of fuel injection immediately after the stroke determination. For this reason, in the fuel injection immediately after the stroke determination, it is possible to supply an appropriate amount of fuel by injecting the fuel of the required injection amount TAU.

  On the other hand, if the first fuel injection after the stroke determination is “½” of the required injection amount TAU, each of the first cylinder 2a and the second cylinder 2b is shown in FIGS. 6 (f) and 6 (g). As shown in the transition of the fuel injection timing and the injection amount, in the first intake stroke after the stroke determination, the fuel of the injection amount “TAU / 2” injected after the stroke determination is taken into the combustion chamber. For this reason, the amount of fuel provided for combustion is insufficient in the first combustion stroke after the stroke determination.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When it is determined that the fuel injected immediately before the stroke determination is not used for combustion, the initial fuel injection amount after the stroke determination is reduced. Thereby, when the fuel injected immediately before the stroke determination is not used for combustion, the amount of fuel provided for combustion in the first combustion stroke after the stroke determination is reduced by reducing the injection amount after the stroke determination. Can be made appropriate. Furthermore, when the fuel injected immediately before the stroke determination is used as the fuel, an appropriate amount of fuel can be injected without reducing the fuel injection amount after the stroke determination.

  (2) The processing shown in FIG. 4 was performed independently for each of the first cylinder 2a and the second cylinder 2b. Thereby, in each of the first cylinder 2a and the second cylinder 2b, it is possible to make the amount of fuel provided for combustion in the combustion stroke immediately after the stroke determination appropriate.

  (3) Before the stroke determination, a stroke in which fuel is injected once every four strokes (near the exhaust top dead center), and a stroke separated by “360 ° CA” from the stroke (near the compression top dead center) In addition, fuel injection was performed. Thereby, the fuel injection before the stroke determination and the fuel injection after the stroke determination can be performed in the same crank angle region. Thereby, the fuel injection timing can be easily set in the crank angle region within one rotation of the crankshaft 32.

  (4) The same stroke determination is made based on whether or not the fuel injection immediately before the stroke determination is made in the stroke (near exhaust top dead center) in the fuel injection once every four strokes. It was determined whether the fuel injected immediately before was used for combustion. This makes it possible to appropriately determine whether or not the fuel has been used for combustion.

  (5) By setting the fuel injection amount before the stroke determination to “½” of the required injection amount TAU, an appropriate amount of fuel will be provided for combustion even in the combustion stroke before the stroke determination, The startability of the engine 1 can be improved.

(6) When the initial fuel injection amount is reduced after the stroke determination, the amount of reduction correction can be determined easily and appropriately by injecting fuel that is “½” of the required injection amount TAU.
(Other embodiments)
Each of the above embodiments may be modified as follows.

  -After the stroke is determined, the mode for reducing the initial fuel injection amount is not necessarily limited to "1/2" of the required injection amount TAU. For example, the amount of fuel injected last time may be subtracted from the required injection amount TAU calculated this time.

  The setting mode of the fuel injection amount before the stroke determination is not necessarily limited to “½” of the required injection amount TAU. For example, the amount of fuel injected last time may be subtracted from the required injection amount TAU calculated this time.

  The calculation mode of the required fuel injection amount is not limited to that illustrated in FIG. For example, the fuel injection amount may be calculated based on at least one of the operating state of the engine 1 and the operating environment, such as calculating the required fuel injection amount in consideration of the operating environment of the engine 1 such as the outside air temperature. .

  -The relative relationship of each cycle of the 1st cylinder 2a and the 2nd cylinder 2b is not restricted to what was illustrated by the said embodiment. The application of the present invention is effective not only when the engine 1 has two cylinders but also when the engine 1 is a single cylinder or a plurality of cylinders of three or more cylinders. In particular, in a 4-stroke engine with 3 or more cylinders, as long as the fuel injection is switched from once every two strokes to once every four strokes before and after the stroke determination, When the number of cylinders is “N”, appropriate fuel injection control cannot be performed only by reducing the amount of fuel injected into the first “N−1” cylinder after stroke determination. In a two-cylinder engine, as illustrated in FIGS. 5, 6, and 8, the strokes (timing) in which fuel is injected once every four strokes are different between cylinders. Even when “360 ° CA” is not deviated, the control as in Patent Document 1 cannot make the fuel injection amount after the stroke determination an appropriate amount.

  -The 4-stroke engine is not limited to the independent intake engine. Further, the engine is not limited to performing intake port injection, and may be a cylinder injection engine. Further, the stroke in which fuel injection is performed once every four strokes and the stroke in which fuel injection is performed once every two strokes are not limited to the vicinity of exhaust top dead center or compression top dead center. You may set suitably according to the request | requirement concerning this operation control.

  The means for determining the stroke is not limited to a means configured to detect the intake pressure of a specific cylinder, and includes a means to detect the rotation angle of the camshaft, for example. Also good.

  ・ Means to determine whether or not the fuel injected just before the stroke determination is used for combustion, or when it is determined not to be used for combustion, reduce the initial fuel injection amount after the stroke determination The means is not limited to the one configured with the electronic control device 20.

The figure which shows the structure of one Embodiment of the fuel-injection control apparatus of the 4-stroke engine concerning this invention. The time chart for demonstrating the process discrimination | determination of the embodiment. The flowchart which shows the process sequence concerning calculation of the fuel injection quantity concerning the embodiment. The flowchart which shows the process sequence of the fuel-injection control concerning the embodiment. The time chart which shows the aspect of the fuel-injection control concerning the embodiment. The time chart which shows the aspect of the fuel-injection control concerning the embodiment. The time chart which shows the aspect of the conventional fuel injection control. The time chart for demonstrating the problem of the said conventional fuel-injection control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2a ... 1st cylinder, 2b ... 2nd cylinder, 6a, 6b ... Injector, 20 ... Electronic control unit, 30 ... Intake pressure sensor, 32 ... Crankshaft, 34 ... Crank angle sensor

Claims (3)

When the stroke discrimination, which is applied to an engine that performs intake port injection and determines which of the four strokes , which is four strokes as one cycle, is completed, fuel injection is performed once every two strokes in each cylinder. In a fuel injection control device for a four-stroke engine that switches from fuel injection to once every four strokes,
Fuel injection once to the 2-stroke, in each of the the angular region injection is made in one-time fuel injection four-stroke and the angular range of "360 ° CA" spaced angular region, the required injection amount " It is done by injecting fuel every 1/2 "
Means for determining, for each cylinder, whether or not the fuel injected immediately before the completion of the stroke determination has been used for combustion;
And a means for setting the first fuel injection amount after the stroke determination in the corresponding cylinder to “½” of the required injection amount when it is determined that the combustion is not performed. Engine fuel injection control device. The means for determining determines whether or not the fuel injection immediately before the determination of the stroke has been performed for the combustion based on whether or not the fuel injection is performed in a stroke in which the injection is performed once every four strokes. The fuel injection control device for a four-stroke engine according to claim 1. The fuel injection control device for a four-stroke engine according to claim 1 or 2,
A fuel injection control device for a four-stroke engine, further comprising means for calculating the required injection amount based on at least one of an operating state and an operating environment of the engine.

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