JP6287347B2 - Engine control device - Google Patents

Description

  The present invention provides an engine control that stops fuel injection when the vehicle is decelerated and performs fuel cut, and cancels the fuel cut and restarts fuel injection when the engine speed decreases to a predetermined fuel return rotation speed. Relates to the device.

  When the vehicle is decelerated, the fuel cut is performed to stop the fuel supply to the engine to improve fuel efficiency and reduce exhaust gas, and when the engine speed decreases to the specified speed (return speed) in the fuel cut state In addition, one that performs control to resume fuel injection is known.

  However, if the rate at which the engine speed decreases in the fuel cut state (decrease rate) is large, after the engine speed reaches the return speed, the engine speed further decreases due to inertia, causing the engine to There is a risk of stalling. Therefore, a technique for avoiding the occurrence of engine stall by correcting the return rotational speed in accordance with the rate of decrease in the rotational speed of the engine has been proposed (see Patent Document 1).

Japanese Patent Laid-Open No. 10-110642

  However, even if the return rotational speed is corrected according to the reduction rate of the rotational speed, the synchronous injection is resumed after the return rotational speed is reached depending on the state (stroke) of the engine when the return rotational speed is reached. Takes time, and there is a concern that engine stall may occur due to a decrease in engine rotation speed.

  The main object of the present invention is to provide an engine control device that can more suitably carry out resumption of fuel supply when fuel cut is performed during deceleration of a vehicle.

  The present invention stops the synchronous fuel injection synchronized with the engine rotation period when the vehicle is decelerated and performs fuel cut, and when the engine speed is reduced to the fuel return speed during the fuel cut. In the engine control device that releases the fuel cut and resumes the synchronous fuel injection, a reduction rate acquisition means for acquiring a reduction rate of the engine rotation speed during the fuel cut, and a fuel return rotation based on the reduction rate of the rotation speed Rotational angle position predicting means for predicting the rotational angle position of the engine when reaching the speed, and asynchronous injection for performing fuel injection to the engine asynchronously when releasing the fuel cut based on the predicted rotational angle position Asynchronous injection determination means that determines whether or not, and when it is determined that asynchronous injection is to be performed, asynchronous injection is performed before the restart of synchronous injection And the asynchronous injection execution means that, characterized in that it comprises a.

  In the above invention, the rotational angle position at the time when the engine rotational speed reaches the fuel return rotational speed is predicted based on the reduction rate of the engine rotational speed. Then, based on the predicted rotational angle position, when releasing the fuel cut, it is determined whether or not to perform fuel injection to the engine asynchronously. To implement. In this case, the engine rotational speed can be increased by asynchronous injection before the synchronous rotational timing comes after the rotational speed of the engine is reduced to the return rotational speed, and hence the occurrence of engine stall can be suppressed.

The block diagram which shows the outline of an engine control system. The flowchart which shows the procedure of the fuel cut process of an engine. The flowchart which shows the procedure of the return process of the engine of a fuel cut state. Map of rotation speed reduction rate and return rotation speed correction amount. The time chart which shows the example of the time change of the rotational speed of an engine.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In this embodiment, an engine control system is constructed for a single-cylinder gasoline engine that repeatedly performs four cycles including intake, compression, expansion, and exhaust stroke as one combustion cycle (720 ° CA). The engine control system uses an electronic control unit (hereinafter referred to as ECU) as a center to control the fuel injection amount, ignition timing, and the like. It is assumed that the engine control system is a two-wheeled vehicle such as a scooter. First, the overall schematic configuration of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and a throttle valve 14 is provided downstream thereof. The throttle valve 14 is provided with a throttle opening sensor 14a for detecting an operation amount of a throttle grip provided on a vehicle handle. An intake pipe pressure sensor 16 for detecting the intake pipe pressure is provided on the downstream side of the throttle valve 14. An electromagnetically driven fuel injection valve 17 is attached near the intake port of the intake pipe 11 and fuel is supplied from a fuel supply device (not shown).

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 24 by the opening operation of the exhaust valve 22. A spark plug 25 is attached to the cylinder head of the engine 10, and a high voltage is applied to the spark plug 25 at a desired ignition timing through an ignition device 26 made of an ignition coil or the like. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 25, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst, and an upstream side of the catalyst 31 is provided with an O2 sensor 32 for detecting the air-fuel ratio of the air-fuel mixture with exhaust as a detection target. Further, the engine 10 is provided with a water temperature sensor 33 for detecting the temperature of the engine cooling water (engine water temperature) and a rotation sensor 34 for outputting a rectangular crank angle signal for every predetermined crank angle as the engine 10 rotates. ing. For example, the rotation sensor 34 outputs a crank angle signal (NE pulse) at a 30 ° CA cycle.

  In addition, a starter 36 (starting device) is mounted on the vehicle, and the starter 36 is driven by the user performing a predetermined starting operation so that initial rotation is applied to the crankshaft of the engine 10. . Although not shown, the vehicle has a continuously variable transmission (CVT) as a power transmission device for transmitting the power generated by the engine 10 to the wheels, and between the engine 10 and the continuously variable transmission. The centrifugal clutch provided is mounted.

  The ECU 40 mainly includes a microcomputer composed of a CPU, ROM, RAM, and the like, and receives detection signals from the various sensors described above. The ECU 40 controls the operating state of the engine 10 by executing various control programs stored in the ROM based on the detection results of the various sensors.

  Specifically, based on the intake pipe pressure PM (engine load) detected by the intake pipe pressure sensor 16 and the rotational speed NE (crank angle signal) of the engine 10 detected by the rotation sensor 34, the fuel injection amount, Ignition timing (ignition timing reference timing) is calculated. In the case of synchronous injection in which fuel injection is performed in synchronization with the rotation cycle of the engine 10, the fuel injection amount from the fuel injection valve 17 is calculated at the fuel injection amount calculation timing (synchronous injection amount calculation timing) in the compression stroke, and the exhaust gas is exhausted. Fuel is injected from the fuel injection valve 17 at a predetermined fuel injection timing (synchronous injection timing) determined in the stroke. Then, the spark plug 25 is determined to be ignited at an ignition timing determined in the vicinity of the compression TDC.

  Further, the ECU 40 determines from the detection signals of the various sensors whether the engine 10 is in four strokes of intake, exhaust, compression, and expansion strokes in each combustion cycle. The stroke determination of the engine 10 is performed based on, for example, a pulse number counted for each output of the NE pulse signal. In addition to this, the stroke determination can be performed using a known technique.

  Further, the ECU 40 controls the execution and release of the fuel cut that stops the synchronous injection of the engine 10 when the vehicle is decelerated. Specifically, the ECU 40 uses the throttle grip rotation operation amount as zero and the rotational speed NE is equal to or higher than a predetermined fuel cut execution speed as a fuel cut execution condition, and when the execution condition is satisfied, Start fuel cut. Then, when the rotational speed NE of the engine 10 decreases to the return rotational speed during the fuel cut, the fuel cut is released and the synchronous injection by the fuel injection valve 17 is restarted (fuel is returned).

  At this time, the ECU 40 of the present embodiment corrects the return rotational speed at which the fuel cut is released according to the rate at which the rotational speed NE of the engine 10 decreases during the fuel cut (hereinafter referred to as the rotational speed decrease rate). While performing a process, the process prediction process which estimates the process of the engine 10 at the time of reaching | attaining the return rotational speed after the said correction | amendment is performed. In the correction process, an engine stall is likely to occur due to an unintended speed decrease as the rate of decrease in the rotation speed increases. Therefore, the correction of the return rotation speed is performed in order to suppress the engine stall.

  Then, according to the stroke predicted by the stroke prediction process, it is determined whether or not to perform asynchronous injection in which fuel is injected at a timing not synchronized with the rotation cycle of the engine 10 before the synchronous injection is resumed.

  That is, when the fuel cut is being performed and the timing at which the rotational speed of the engine 10 becomes the return rotational speed is later than the fuel injection timing in the synchronous injection, at the synchronous injection timing, The fuel cannot be injected with the calculated fuel injection amount. In addition, if the engine is waiting for combustion in the period from when the return rotational speed is reached until the combustion by the synchronous injection is resumed, the rotational speed of the engine 10 further decreases during that time, which may cause engine stall. .

  Therefore, when the timing at which the return rotational speed is reached is after the synchronous injection timing, asynchronous injection is performed prior to the execution of synchronous injection. In this case, before the synchronous injection is resumed, the rotational speed of the engine 10 can be increased by the combustion by the asynchronous injection, and as a result, the occurrence of engine stall can be suppressed. At this time, the fuel injection amount of the asynchronous injection may be a predetermined value set in advance. Note that the fuel injection amount of asynchronous injection may be calculated using the return rotation speed as a parameter.

  On the other hand, when performing asynchronous injection, fuel consumption accompanying asynchronous injection occurs. Further, when the timing (stroke) at which the return rotational speed is reached is close to the fuel injection timing in the next synchronous injection, problems associated with the rotational speed of the engine 10 being lower than the return rotational speed are less likely to occur. Thus, when the period of asynchronous injection is limited to a predetermined range, it is possible to suitably suppress the occurrence of engine stall while improving fuel consumption.

  For example, asynchronous injection is performed when the timing of the return rotational speed is after the fuel injection timing in the synchronous injection and before the ignition timing. For example, in this embodiment, asynchronous injection is performed when it is determined that the intake stroke. In this case, since the fuel injected into the combustion chamber 23 by the asynchronous injection is combusted at the ignition timing before the combustion by the synchronous injection is performed, the rotational speed of the engine 10 can be increased before the synchronous injection is restarted. . When asynchronous injection is performed in the intake stroke, fuel can be supplied to the combustion chamber 23 more suitably.

  FIG. 2 shows a flowchart of the fuel cut processing procedure of the engine 10. FIG. 3 shows a flowchart of the procedure of the return process from the fuel cut state. The following processing is repeatedly performed in the operating state of the engine 10.

  In FIG. 2, it is determined in step S11 whether or not a fuel cut has been performed and the fuel cut flag F = 0 (zero). If the fuel cut flag F = 0 and an affirmative determination is made, the routine proceeds to step S12, where it is determined whether or not a fuel cut execution condition is satisfied. If a positive determination is made, the process proceeds to step S13, and the fuel cut flag F = 1 is set. When the fuel cut flag F = 1, the synchronous injection of fuel from the fuel injection valve 17 is stopped.

  If a negative determination is made in step S11, that is, if the fuel cut flag F = 1, the process proceeds to step S14, and it is determined whether or not the rotational speed NE of the engine 10 is equal to or lower than the return rotational speed Nth. When an affirmative determination is made, the process proceeds to step S15, and the fuel cut flag F = 0 is returned. If a negative determination is made in steps S12 and S14, this process is terminated.

  In FIG. 3, it is determined in step S20 whether or not the fuel cut flag F = 1. If an affirmative determination is made, the process proceeds to step S21 to calculate a reduction rate of the rotation speed. For example, based on the detection signal of the rotation sensor 34, the rate of decrease in rotation speed is calculated from the difference in average rotation speed over a predetermined period. In the subsequent step S22, the return rotational speed is corrected based on the rotational speed reduction rate. For example, the ROM stores a map of the relationship between the rotational speed reduction rate and the return rotational speed correction amount as shown in FIG. 4, and the rotational speed reduction rate calculated in step S21 is applied to the map. Thus, the return rotation speed correction amount is calculated, and the return rotation speed is corrected using the correction amount.

  In a succeeding step S23, it is determined whether or not it is time to calculate the fuel injection amount. Here, it is determined whether or not it is a predetermined calculation time in the compression stroke. When an affirmative determination is made, the process proceeds to step S24, in which it is determined whether or not the engine speed NE is less than the return speed Nth by the next synchronous injection timing in the combustion cycle. For example, calculate the rotation speed at the next synchronous injection timing from the rate of decrease in the rotation speed and the time required to reach the next calculation time, and whether the rotation speed is less than the corrected return rotation speed Determine whether or not.

  In this case, if the engine rotational speed NE is less than the return rotational speed Nth by the next synchronous injection timing, synchronous injection at the synchronous injection timing in the next exhaust stroke can be performed, and step S24 is affirmatively determined. The When an affirmative determination is made in step S24, the process proceeds to step S30 to perform synchronous injection. That is, synchronous injection is performed as the initial fuel injection when the fuel cut is released. In step S29, the fuel cut flag F is reset to zero.

  On the other hand, if a negative determination is made in step S24, the process proceeds to step S25, in which it is determined whether or not the engine rotational speed NE is less than the return rotational speed Nth by the next synchronous injection amount calculation timing. When an affirmative determination is made, the process proceeds to step S26, and the crank angle Tn at the time of reaching the return rotational speed is predicted. For example, the difference ΔNE (ΔNE = NE−Nth) between the current rotation speed NE and the return rotation speed Nth is calculated. Then, the difference ΔNE is divided by the amount of change per unit time of the rotational speed NE. As a result, the time (T1) required to reach the return rotational speed is obtained.

  Then, the time (T1) to reach the return rotational speed is converted into a crank angle. That is, the time T1 is divided by the average value (ΔT) of the time between NE pulses. The crank angle Tn (Tn = T0 = T1 / ΔT) at the return rotational speed is calculated by adding the crank angle (T0) of the current stroke to this value (T1 / ΔT).

  In a succeeding step S27, it is determined whether or not the asynchronous injection is performed based on the crank angle Tn predicted in the step S26. Here, the stroke (return stroke) which becomes the return rotation speed is obtained from the crank angle Tn. Then, it is determined that the asynchronous injection is performed when the return stroke is the intake stroke, and it is determined that the asynchronous injection is not performed when the other strokes are the compression, expansion, and exhaust strokes.

  When it determines with implementing asynchronous injection by step S27, it progresses to step S28 and implements asynchronous injection. In step S29, the fuel cut flag F is reset to zero. In addition, this process is complete | finished when negative determination is carried out by step S21, S24, S25, S27.

  Next, an execution example of the above process will be described. FIG. 5 shows a time chart showing an example of a change over time in the rotational speed of the engine 10. In FIG. 5, it is assumed that the fuel cut flag F = 1 in the initial period. In FIG. 5, times t1 and t5 are synchronous injection amount calculation timings in the compression stroke, and times t2 and t6 are synchronous injection timings in the exhaust stroke.

  At time t1, when it is time to calculate the fuel injection amount in the compression stroke, a reduction rate of the rotational speed NE is calculated, and the return rotational speed is corrected based on the reduction rate of the rotational speed. Here, the return rotation speed Nth is corrected from Nth1 (base value) to Nth2. At time t1, the rotational speed NE is not less than the return rotational speed Nth2 by the next synchronous injection timing (t2), and the rotational speed NE is restored to the return rotational speed Nth2 by the next synchronous injection amount calculation time (t5). Determined to be less than Further, here, the predicted timing at which the rotational speed NE is less than the return rotational speed Nth2 is taken as the intake stroke, and it is determined that asynchronous injection is performed in this intake stroke.

  Thereafter, when the actual rotational speed NE becomes the return rotational speed Nth2 at time t3, asynchronous injection of the intake stroke is performed. Then, when ignition is performed at time t4 near the compression TDC, initial combustion at the time of resuming combustion is performed. As a result, the rotational speed NE increases.

  Thereafter, the fuel injection amount of synchronous injection is calculated at time t5, and synchronous injection is performed at time t6. In FIG. 5, when the asynchronous injection at time t3 is not performed, the first fuel injection at the time of resuming combustion is at time t6, and there is concern about engine stalls due to waiting for the increase in rotation after time t6. By performing the asynchronous injection at the time t3, the first fuel injection at the time of resuming the combustion is performed at the time t3, and the engine stall can be suppressed.

  According to the present invention, the following excellent effects can be obtained.

  (1) When the fuel cut is performed, depending on the engine state (stroke) when the rotation speed of the engine 10 is reduced to the fuel return rotation speed, it takes time from the return rotation speed to the restart of combustion. If the engine speed is further reduced due to inertia, engine stall may occur. Therefore, based on the rate of decrease in the rotational speed of the engine 10 during the fuel cut, the rotational angle position when the rotational speed of the engine 10 reaches the fuel return rotational speed is predicted. Then, based on the predicted rotational angle position, it is determined whether or not fuel injection to the engine 10 is performed asynchronously. When it is determined that the fuel injection is performed, asynchronous injection is performed before the synchronous injection is restarted. In this case, the rotational speed of the engine 10 can be increased by asynchronous injection before the synchronous injection timing comes after the rotational speed of the engine 10 decreases to the return rotational speed, thereby suppressing the occurrence of engine stall. it can.

  (2) Asynchronous injection is performed when the predicted rotational angle position when reaching the fuel return rotational speed is after the fuel injection timing in each combustion cycle and before the next ignition timing. To do. In this case, the fuel that has been asynchronously injected at a timing prior to the ignition timing is injected at the next ignition timing, so that the engine speed can be increased before the synchronous injection is performed, and as a result Occurrence can be suppressed.

  (3) When performing asynchronous injection in the intake stroke, the fuel can be supplied more appropriately to the combustion chamber 23, and the rotational speed of the engine 10 can be suitably increased.

  (4) When the rate of decrease in the rotational speed is large, the degree of further decrease in the rotational speed of the engine 10 due to inertia when the fuel return rotational speed is reached increases, and the possibility of causing an engine stall increases. Therefore, by correcting the return rotational speed according to the rate of decrease in rotational speed, the effect of suppressing engine stall can be enhanced according to the rate of decrease in rotational speed of the engine 10.

  (5) In the case of a single-cylinder engine, fuel injection is performed every 720 ° CA. Therefore, depending on the stroke when the engine 10 reaches the return rotation speed, more time is required until the synchronous injection is resumed. become. Therefore, the occurrence of engine stall in the single cylinder engine can be suitably suppressed by applying the configuration of the present invention to the single cylinder engine.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows.

  In the above, an example in which the return rotation speed is corrected based on the rate of decrease in the rotation speed has been described, but the process of correcting the return rotation speed, that is, the process of step S22 in FIG. 3 can be omitted. In this case, in order to improve fuel consumption, it is preferable that the return rotational speed is set as low as possible according to the rate of decrease in the rotational speed. On the other hand, in the present embodiment, asynchronous injection is performed as necessary based on the stroke (return stroke) when the rotation speed of the engine 10 becomes the return rotation speed. For this reason, even if the return rotational speed is set to a low rotational speed, it is possible to prevent the rotational speed of the engine 10 from further lowering than the return rotational speed, which in turn improves fuel consumption and suppresses engine stall. Both can be achieved.

  In the above description, the single-cylinder engine is described as an example. However, the engine control system having the configuration of the present invention can also be applied to a four-cylinder engine (multi-cylinder engine) mounted on a vehicle such as an automobile. This can enhance the effect of suppressing the occurrence of engine stall in a vehicle such as an automobile.

  In step S26 in FIG. 3, the return stroke may be predicted in consideration of various parameters related to deceleration. For example, it is possible to predict the stroke when the return rotational speed is reached in consideration of a temperature detection value by a temperature sensor (not shown), a gear ratio in a geared vehicle (two-wheeled vehicle), and the like. In this case, the accuracy of predicting the return stroke when reaching the return rotation speed can be improved.

  Asynchronous injection may be performed a predetermined number of times (two or more times). For example, asynchronous injection may be repeatedly performed until the rotational speed of the engine 10 becomes equal to or higher than the return rotational speed.

  -When asynchronous injection is performed, it is preferable that the fuel injection timing is set in the first half of the intake stroke. By injecting fuel in the first half of the intake stroke, fuel can be supplied to the combustion chamber 23 more appropriately, and the rotational speed NE of the engine 10 can be suitably increased by performing asynchronous injection.

  In the above description, whether to perform asynchronous injection is determined based on the stroke when the rotational speed NE becomes the return rotational speed Nth. In addition to this, it is determined whether or not to perform asynchronous injection based on the crank angle when the rotational speed NE becomes the return rotational speed Nth, the pulse number counted every time the NE pulse signal is output, and the like. May be.

  In the above description, when it is determined that the fuel injection amount is calculated, it is determined whether the rotational speed NE is less than the return rotational speed Nth by the next fuel injection amount calculation timing. In addition to this, it may be determined whether or not the rotational speed NE is less than the return rotational speed Nth by the next fuel injection amount calculation time, regardless of the fuel injection amount calculation time. For example, for each predetermined NE pulse, it may be determined whether or not the rotational speed NE is less than the return rotational speed Nth by the next fuel injection amount calculation timing. In this case, the detection accuracy of the timing at which the rotational speed NE becomes the return rotational speed Nth can be increased.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 26 ... Ignition device, 40 ... ECU.

Claims (6)

When the vehicle is decelerated, the fuel is cut by stopping the synchronous injection of the fuel synchronized with the rotation period of the engine (10), and the engine speed is reduced to the fuel return speed during the fuel cut. In the engine control device for releasing the fuel cut and restarting the synchronous injection of fuel,
A reduction rate acquisition means for acquiring a reduction rate of the rotational speed of the engine during execution of the fuel cut;
A rotation angle position prediction means for predicting a rotation angle position of the engine when reaching the fuel return rotation speed based on the rate of decrease in the rotation speed;
Asynchronous injection determination means for determining whether or not to perform asynchronous injection for performing asynchronous fuel injection to the engine when releasing the fuel cut based on the predicted rotational angle position;
Asynchronous injection performing means for performing asynchronous injection before restarting the synchronous injection when it is determined to perform the asynchronous injection;
An engine control device comprising: The asynchronous injection determination means performs the asynchronous injection when the predicted rotational angle position is after the fuel injection timing of the synchronous injection in each combustion cycle and before the next compression stroke. The engine control device according to claim 1 for determination. The asynchronous injection determining means determines that the asynchronous injection is to be performed when the predicted rotation angle position is an intake stroke;
The engine control apparatus according to claim 1, wherein the asynchronous injection execution unit performs the asynchronous injection in the intake stroke.   The engine control device according to any one of claims 1 to 3, further comprising a return rotation speed correction unit that corrects the fuel return rotation speed based on a decrease rate of the rotation speed.   The engine control device according to any one of claims 1 to 4, wherein the rotation angle position prediction means predicts the rotation angle position at a calculation timing of a fuel injection amount in the synchronous injection.   The engine control apparatus according to claim 1, wherein the engine is a single cylinder engine.

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