JP2011157947A - Idle stop control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an idle stop control device, solving such a problem that injected fuel cannot be ignited when an idle stop request is changed. <P>SOLUTION: When a cylinder indetermination period t11-t21, in which a result of cylinder determination is not acquired, is a period including a starter mask period t11-t20 set caused by drive of a starter motor according to the change of the idle stop request, and a determination period t20 and t21 required for cylinder determination after the starter mask period is finished, and under a condition where an engine speed NE is decreased to a speed in which the cylinder indetermination period is two strokes or less, the drive of the starter motor is started to restart the engine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an idle stop control device applied to an internal combustion engine having an idle stop function.

  In recent years, vehicles equipped with an engine (internal combustion engine) having an idle stop function are increasing. For example, when the driver stops the vehicle, the engine is automatically stopped. After that, when the driver performs an operation to start the vehicle, the engine is automatically cranked with the starter and restarted. Start.

  Here, when an automatic stop request is generated, the fuel injection is cut and the engine rotational speed NE is decreased, but a request change (Change of Mind) that an automatic restart request is generated during this rotational decrease period. May occur. In this case, it is a general control that the starter is driven and restarted after the engine speed NE drops to zero. However, in this case, the time required from when the restart request is generated until the actual restart is increased by the amount of time to wait for the drop to NE = 0, and the restart cannot be performed quickly.

  Therefore, in the “advance control” and “advance control” described later, when the request is changed, the starter is driven without waiting for the engine speed to drop to zero, so that it can be restarted quickly. (See Patent Documents 1 to 3).

  Generally, a starter rotates a pinion with a motor, pushes out the pinion with an actuator, meshes the pinion with a ring gear connected to the crankshaft of the engine, and drives the ring gear to rotate so that the engine is cranked. It has become. However, if the pinion tries to mesh with the ring gear in a state where the difference in rotational speed between the pinion and the ring gear is large, the pinion may not mesh smoothly with the ring gear and noise may be generated.

  Therefore, in the advance control, the pinion is driven to rotate when a request change occurs, and the rotational speed of the pinion is synchronized with the rotational speed of the ring gear to reduce the difference between the rotational speeds of the two. Then, after the synchronization is made, the pinion is pushed out and meshed with the ring gear to start cranking, thereby quickly restarting.

  However, it is difficult to synchronize if the engine speed NE is low when the request change occurs. Therefore, in the above-mentioned advance control, when NE at the time of request change occurrence is lower than a predetermined threshold, after the request change occurs, the engine rotation (rotation of the ring gear) becomes low before the stop, and then the starter The pinion is pushed out and meshed with the ring gear, and then the pinion is rotated to start cranking.

JP 2002-122059 A Japanese Patent Laying-Open No. 2005-330813 JP 2002-70699 A

  Incidentally, in a four-cycle engine that sequentially performs four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke, in order to perform control so that fuel injection and ignition are performed at an optimal timing, the current stroke is the four strokes. It is indispensable to know which one is. Therefore, it is necessary to perform a process for discriminating each stroke (cylinder discrimination) based on detection signals output from the crank angle sensor and the cam angle sensor (cylinder discrimination sensor).

  However, when the starter motor is driven, noise is superimposed on the detection signals of the crank angle sensor and the cam angle sensor due to a large current flowing through the motor. For this reason, it is necessary to perform starter masking such as stopping the cylinder discrimination process during a period in which the noise is superimposed (starter mask period).

  The starter mask period is generally set to a period from when the starter motor is driven to when a predetermined time elapses. When the starter motor is driven with the engine speed NE being zero, the starter mask period is set. There is no particular problem with masking. However, when the starter motor is driven in a state where the crankshaft is rotated by the above-described advance control or advance control, the following problem illustrated in FIG. 3 occurs.

  FIG. 3 shows the asynchronous injection in which the starter motor is driven to perform the advance control at the time t10 when the request change occurs, and the fuel is injected regardless of which of the four strokes the current stroke is. Has been implemented. Since the example in FIG. 3 is a four-cylinder engine, fuel is injected into all cylinders at time t10. Further, assuming a port injection type engine in which fuel is injected into the intake port, the asynchronously injected fuel is sequentially sucked into the combustion chamber at the timings indicated by symbols i1 to i4. Therefore, the # 1 cylinder is required to ignite the fuel injected asynchronously at the time point i1 at the time point ts.

  However, since starter masking is started from time t10 when driving of the starter motor is started, a cylinder discrimination result cannot be obtained in the cylinder non-discrimination periods t10 to t21 including the mask period (50 ms in the example of FIG. 3). As a result, there arises a problem that the # 1 cylinder cannot be ignited at time ts. In this case, the exhaust emission deteriorates and the rise of the engine rotational speed NE after the restart is requested is deteriorated, resulting in poor drivability.

  In addition, in order to determine the cylinder based on the detection signals of the crank angle sensor and the cam angle sensor after the mask period has elapsed, the crankshaft needs to rotate more than a predetermined angle. Determination is complete. In other words, in the example of FIG. 3, the cylinder non-discrimination period t10 to t21 is the period from when the request change occurs until the third stroke elapses, including the stroke at time t10 when the request change occurs.

  By the way, when restarting with the engine speed NE being zero instead of restarting due to a request change, the NE during the masking period is low, so the crankshaft during the masking period (50 ms) The amount that rotates is small. Therefore, the cylinder non-discrimination period does not become longer over three strokes, and the above problem does not occur.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to provide an idle stop that solves the problem that the injected fuel cannot be ignited due to a change in the idle stop request. It is to provide a control device.

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

  According to the first aspect of the present invention, there is provided an internal combustion engine that sequentially performs four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke in a cylinder, and has an idle stop function that automatically stops and restarts. Cylinder discrimination means for discriminating which of the four strokes is the stroke performed in the cylinder based on a detection signal output from the cylinder discrimination sensor, and rotational driving force to the crankshaft of the internal combustion engine A period in which noise is superimposed on the detection signal due to the drive of the starter motor that provides the starter mask period is set as a starter mask period, and the starter mask means for stopping the discrimination by the cylinder discrimination means in the starter mask period; and When the request for automatic restart occurs during the rotation descent period in which the fuel injection is cut to reduce the engine rotation speed with the occurrence of the request for automatic stop When a request changes Tsu, the engine rotational speed is assumed that and a drive control module requests changes be restarted by driving the starter motor without waiting to drop to zero.

  And a starter mask period that is set by driving the starter motor when the request change occurs, and a determination period required for the determination by the cylinder determining unit after the starter mask period ends. When the period is a cylinder non-discrimination period in which the discrimination result by the cylinder discrimination means cannot be obtained, the engine speed decreases to a speed at which the cylinder non-discrimination period is equal to or less than two of the four strokes. The start of the starter motor is permitted to be started by the request change time control means on condition that the starter motor is in a state of being in a closed state.

  According to this, since the start of the starter motor is permitted on the condition that the engine rotational speed has been reduced to a speed at which the cylinder non-discrimination period becomes 2 strokes or less, At the time when it is desired to ignite the fuel injected at the same time or immediately after the drive, the cylinder non-discrimination period ends and the cylinder discrimination result by the cylinder discrimination means can be acquired. Therefore, since the ignition can be performed, it is possible to avoid the deterioration of exhaust emission and the deterioration of drivability due to the fact that the injected fuel cannot be combusted with the occurrence of the request change.

  According to a second aspect of the present invention, the engine speed is reduced to a speed at which the cylinder non-discrimination period is not more than two of the four strokes. The fuel injection by the control means is permitted.

  According to the first aspect of the present invention, for example, when the engine speed NE at the time when the request change occurs is high, the NE is increased to such a speed that the cylinder non-discrimination period becomes 2 strokes or less. The starter motor starts to be driven after waiting for the motor to descend. In such a case, if the fuel is injected prior to the start of driving the starter motor after the request change occurs, there may occur a situation in which the cylinder non-discrimination period has not yet ended when it is desired to ignite the injected fuel. .

  In the above-mentioned invention in view of this point, fuel injection by the request change time control means is performed on the condition that the engine rotational speed is reduced to a speed at which the cylinder non-discrimination period is 2 strokes or less. Since the permission is granted, the fuel can be ignited after the cylinder non-discrimination period ends. Therefore, the ignition can be reliably performed.

  In the third aspect of the present invention, it is assumed that the cylinder discriminating means, the starter mask means, and the request change time control means are provided in the same manner as in the first aspect. And a starter mask period that is set by driving the starter motor when the request change occurs, and a determination period required for the determination by the cylinder determining unit after the starter mask period ends. When the period is a cylinder non-discrimination period in which the discrimination result by the cylinder discrimination means cannot be obtained, the engine speed decreases to a speed at which the cylinder non-discrimination period is equal to or less than two of the four strokes. Fuel injection by the request change time control means is permitted on the condition that it is in a state of being

  According to this, the first fuel injection (for example, asynchronous injection) is performed on the condition that the engine rotational speed is reduced to a speed at which the cylinder non-discrimination period becomes 2 strokes or less. If the starter motor is started at the same time as the injection or immediately before the injection, the cylinder non-discrimination period ends and the cylinder discrimination result obtained by the cylinder discrimination means is acquired at the time when the injected fuel is desired to be ignited. it can. Therefore, since the ignition can be performed, it is possible to avoid the deterioration of exhaust emission and the deterioration of drivability due to the fact that the injected fuel cannot be combusted with the occurrence of the request change.

  According to a fourth aspect of the present invention, the first ignition after the request change has occurred is performed simultaneously with the end of the cylinder non-discrimination period. Can be made.

  According to a fifth aspect of the present invention, when the engine speed after the request change occurs is equal to or less than a predetermined threshold value, the control unit at the time of request change has a cylinder non-discrimination period 2 of the four strokes. It has a judging means which judges that it becomes below a stroke, and the threshold value is variably set according to the operating state of the internal-combustion engine.

  For example, if the engine speed at the time of request change is high, or if the internal combustion engine's lubricating oil temperature is low and the friction loss is large, the mask will not change even if the engine speed at the time of request change is the same. The amount that the crankshaft rotates during the period (for example, 50 ms) decreases. Therefore, the possibility that the cylinder non-discrimination period becomes longer over three strokes is reduced.

  In view of this point, in the above-described invention, the engine rotation speed is such that the cylinder non-discrimination period is equal to or less than two strokes according to the operating state of the internal combustion engine (for example, the decrease speed of the engine rotation speed or the lubricating oil temperature when the request is changed) Since the threshold value for determining whether or not is variably set, the threshold value can be optimized. Specifically, when the engine speed NE at the time of changing the request is higher than a threshold value, the starter motor is started after waiting (waiting) for NE to drop to the threshold value. By setting the threshold value higher as the lowering speed of the engine rotation speed is higher or the lubricating oil temperature is lower, the waiting time can be shortened and the time required for restart can be shortened.

The figure explaining the hardware constitutions of an internal-combustion engine to which the idle stop control device concerning one embodiment of the present invention is applied. The figure explaining the outline | summary of the restart control implemented when a restart request | requirement generate | occur | produces in the middle of NE falling by the engine automatic stop. The time chart for demonstrating the problem which arises when not implementing this invention. The time chart for demonstrating the effect exhibited when implementing this invention. The flowchart which shows the process sequence of the automatic restart implemented when the request | requirement of an automatic restart generate | occur | produces in the one embodiment of this invention in the middle of the engine rotational speed falling with the request | requirement of an automatic stop.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In this embodiment, a reciprocating engine (internal combustion engine) for a four-wheeled vehicle is targeted, and the engine is a four-cycle engine that sequentially performs four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke. The engine is an ignition type gasoline engine using regular fuel as gasoline and a port injection type engine that injects fuel into an intake port. Further, the engine has an idle stop function for automatic stop and automatic restart.

  FIG. 1 is a diagram showing a hardware configuration of an engine. An electronic control unit (ECU 10) includes a crank angle sensor 21 (cylinder discrimination sensor), a cam angle sensor 22 (cylinder discrimination sensor), a coolant temperature sensor 23, and an air flow. Detection signals from various sensors such as the meter 24 are input.

  The crank angle sensor 21 detects the rotation angle of the crankshaft 31 (output shaft) of the engine 30. The cam angle sensor 22 detects that the cam shaft 32 of the engine 30 has made one revolution (one combustion cycle has elapsed). The cooling water temperature sensor 23 detects the temperature of the engine cooling water. The air flow meter 24 detects the amount of intake air flowing through the intake pipe 34 (more precisely, the mass flow rate of intake air flowing per unit time).

  The ECU 10 has a microcomputer, and performs processing (NE calculation processing) for calculating the rotational speed of the crankshaft 31 (engine rotational speed NE) based on the angle signal output from the crank angle sensor 21. Further, the ECU 10 performs a cylinder discrimination process and a crank angle calculation process, which will be described later, based on a reference position signal (detection signal) output from the crank angle sensor 21 and a cylinder discrimination signal (detection signal) output from the cam angle sensor 22. .

  The NE calculation process and cylinder discrimination process will be described in more detail. An angle signal and a reference position signal are output from the crank angle sensor 21, and the crankshaft 31 rotates at a predetermined crank angle (for example, 10 degrees). Output every time. The reference position signal is output every time the specific position of the crankshaft 31 passes a reference position (for example, TDC (Top Dead Center)). The cylinder discrimination signal output from the cam angle sensor 22 is output every time the camshaft 32 makes one revolution (the crankshaft 31 makes two revolutions).

  Then, the ECU 10 calculates the engine speed NE by counting the number of times the angle signal output from the crank angle sensor 21 is output per unit time (NE calculation processing). Further, based on the reference position signal output from the crank angle sensor 21 and the cylinder determination signal output from the cam angle sensor 22, it is determined for each cylinder which is the current stroke in the four strokes of the combustion cycle. (Cylinder discrimination processing) Further, based on the cylinder discrimination result and the angle signal, how much the current crank angle is rotated with respect to a reference position (for example, TDC for starting the compression stroke) is calculated (crank angle calculation processing). Note that the ECU 10 when performing the cylinder discrimination process corresponds to “cylinder discrimination means”.

  The ECU 10 controls the injection amount and the injection timing of the fuel flowing into the combustion chamber 30a by controlling the operation of the fuel injection valve 33 based on detection signals from the various sensors 21 to 24. The fuel injection valve 33 is attached to the intake pipe 34 and is a port injection system that injects fuel into the intake pipe 34.

  Further, the ECU 10 controls the amount of intake air flowing into the combustion chamber 30a by controlling the operation of the throttle valve 35 based on detection signals from the various sensors 21 to 24. Specifically, the target intake air amount is calculated based on the engine rotational speed NE and the engine load (for example, the intake air amount). For example, the target intake air amount is increased as the NE is higher and the load is higher. Then, the opening degree of the throttle valve 35 is controlled so as to be the target intake air amount. The throttle valve 35 is driven by an electric motor 36 (actuator) to adjust the opening of the intake pipe 34.

  Further, the ECU 10 controls the timing at which the air-fuel mixture is ignited by controlling the operation of the ignition device 37 based on detection signals from the various sensors 21 to 24. Specifically, the ignition timing is advanced so as to approach the optimum ignition timing MBT (minimum advance for the torque) immediately before the TDC at which the compression stroke starts, while the ignition timing is delayed when knocking is detected. Ignition timing control such as making it horn. Since the intake pressure or the intake air amount is unstable when the engine is started, the ignition timing is controlled to be fixed at, for example, BTDC 10 deg. However, when the engine is automatically restarted after changing the idle stop request described later, ignition is performed at the end of the cylinder non-discrimination period (details will be described later).

  Next, the fuel injection control will be described in more detail.

  The ECU 10 calculates the target injection amount of fuel as follows, and controls the valve opening time of the fuel injection valve 33 so as to be the target injection amount. That is, the basic injection amount is calculated based on the engine rotational speed NE and the engine load (for example, intake pressure or intake amount), and the target injection amount is calculated by applying various corrections to the basic injection amount.

  However, if the operating state of the engine 30 is during the start-up period, the intake air amount (or intake air pressure) is unstable and the reliability of the detected value of the air flow meter 24 is low. Further, when the engine speed NE is equal to or less than a predetermined value (for example, 200 rpm or less), the NE calculation accuracy is low. Therefore, during the start-up period, the accurate engine speed NE and the engine load cannot be acquired, so that the basic injection amount described above cannot be calculated. Therefore, during such a start-up period, instead of calculating the basic injection amount, a preset amount (start-up injection amount) is injected as the target injection amount.

  The fuel injection valve 33 is provided for each of the plurality of cylinders, and an independent injection method is employed in which fuel is injected into each cylinder once per combustion cycle. This independent injection is performed at a timing advanced by a predetermined amount from the TDC at which the intake stroke is started. That is, it can be said that the independent injection is synchronous injection synchronized with the crank angle. The fuel thus synchronously injected is sucked into the combustion chamber 30a together with the intake air in the immediately following intake stroke.

  On the other hand, when the engine is automatically restarted after changing the idle stop request described later, or when it is desired to accelerate the vehicle, asynchronous injection is performed in which fuel is simultaneously injected into a plurality of cylinders (details will be described later). For example, as shown in FIG. 3, the fuel injected asynchronously at time t10 is sequentially sucked into the combustion chamber 30a at the timings indicated by reference numerals i1 to i4.

  Next, the configuration of the starter 40 shown in FIG. 1 will be described.

  The starter 40 is a so-called pinion push-out starter, and includes a starter motor 42, a pinion 41 that is rotationally driven by the starter motor 42, and an electromagnetic actuator 43 that pushes the pinion 41. The pinion 41 is provided so as to be movable in the axial direction. The electromagnetic actuator 43 is provided with a plunger 44 and a solenoid 45 for driving the plunger 44, and the driving force of the plunger 44 is transmitted to the pinion 41 via the lever 46 and the like.

  Then, the ECU 10 controls the energization of the electromagnetic actuator 43 to move the plunger 44 in the pinion pushing direction to push out the pinion 41, and the ring gear 31 a connected to the crankshaft 31 of the engine 30. Bite into. Further, the pinion 41 is rotationally driven by controlling the energization of the starter motor 42 by the ECU 10.

  Next, the idle stop function of the engine 30 will be described.

  The ECU 10 executes engine automatic stop / start control (so-called idle stop control) by executing an engine automatic stop / start control routine (not shown). In this engine automatic stop start control, when the driver performs a deceleration operation (accelerator fully closed, brake operation, etc.) while the vehicle is running and a deceleration request is generated, or when the vehicle is stopped, an engine automatic stop request is issued. It is determined that it has occurred, and combustion (fuel injection and / or ignition) of the engine 30 is stopped and the engine 30 is automatically stopped. After that, when the deceleration request is canceled while the vehicle is running, or while the vehicle is stopped, the driver performs a preparation operation for starting the vehicle (brake release, shift lever operation, etc.) or a start operation (accelerator depression, etc.). When it is determined that an engine restart request has occurred, the engine 30 is restarted.

  In the present embodiment, when a request change such as a change in the request content of the idle stop function occurs so that a restart request is generated during a rotation descent period in which the engine rotation speed NE decreases due to the automatic stop of the engine 30, In order to restart quickly, restart control for driving the starter 40 is performed without waiting for NE to drop to zero. However, the content of the restart control varies as shown in FIG. 2 according to the timing at which the restart request is generated during the rotation descent period.

<Autonomous return control>
The engine restart request is made in a first rotational speed region (N1 <NE) where NE is higher than the first rotational speed N1 (for example, 600 rpm) during a period of time during which the engine rotational speed NE decreases due to the automatic stop of the engine 30. When (change request) occurs, it is determined that the engine 30 can be restarted without performing cranking by the starter 40, and autonomous return control is executed. In this autonomous return control, fuel injection and ignition are restarted without performing cranking by the starter 40, and the engine 30 is restarted.

<Previous control>
During the rotation descent period, a second rotation in which NE is equal to or lower than a predetermined threshold Nth (for example, 400 rpm) set to a value lower than the first rotation speed N1 and higher than the second rotation speed N2 (for example, 250 rpm). When the engine restart request is generated in the speed region (N2 <NE ≦ Nth), the advance control described below is performed. That is, since the rotational speed of the ring gear 31a is relatively high, it is determined that the pinion 41 cannot be smoothly meshed with the ring gear 31a unless the rotational speed of the pinion 41 is synchronized with the rotational speed of the ring gear 31a. Execute. In this advance control, the starter motor 42 synchronizes the rotational speed of the pinion 41 with the rotational speed of the ring gear 31a to reduce the difference between the rotational speeds, and then the electromagnetic actuator 43 meshes the pinion 41 with the ring gear 31a to start the starter 40. The cranking is started and the engine 30 is restarted.

  When NE is in the region (standby region) where NE is equal to or lower than the first rotational speed N1 and is higher than the predetermined threshold value Nth (Nth <NE ≦ N1) during the rotation descent period, the autonomous return control is also performed. No advance control is performed. Therefore, in this case, after the engine restart request is generated, the forward control is performed when NE drops to the threshold value Nth. The technical idea of setting the threshold value Nth will be described in detail later.

  Note that the ECU 10 when performing the advance control or when controlling to wait for the NE to fall to the threshold value Nth corresponds to “request change control means”.

<First-out control>
When an engine restart request is generated in the third rotation speed region (NE ≦ N2) where NE is equal to or lower than the second rotation speed N2 during the rotation descent period, first-out control described below is performed. That is, since the rotational speed of the ring gear 31a is relatively low, it is determined that the pinion 41 can be smoothly meshed with the ring gear 31a without synchronizing the rotational speed of the pinion 41 with the rotational speed of the ring gear 31a. Execute. In this advance control, after the pinion 41 is engaged with the ring gear 31a by the electromagnetic actuator 43, or during the engagement, the starter motor 42 is rotated to start the cranking by the starter 40 and restart the engine 30. Let

  When the advance control and the advance control are performed, asynchronous injection is performed simultaneously with the request change. On the other hand, when a request change occurs in the standby area, asynchronous injection is performed when NE drops to the threshold value Nth. These asynchronous injections are performed only once. Further, the injection amount by asynchronous injection is the above-described start-time injection amount.

  For reference, the technical significance of asynchronous injection will be described below. Compared to the direct injection type in which fuel is directly injected into the combustion chamber 30a, in the case of the port injection type as in the present embodiment, there is a time lag from when the fuel is injected until it is sucked into the combustion chamber 30a. Therefore, in order to quickly restart after occurrence of a request change, it is desirable to inject fuel at the quickest possible timing after the request change occurs. Therefore, if it is not the waiting area, asynchronous injection is performed at the same time as the request change occurs. Further, in order to control the fuel injection valve 33 so as to perform the synchronous injection, the time required for the arithmetic processing of the ECU 10 becomes longer than in the case of performing the asynchronous injection. For this reason, it is difficult to inject fuel at the time of occurrence of a request change due to restrictions on the arithmetic processing capability of the ECU 10. Therefore, if it is not the waiting area, asynchronous injection is performed at the same time as the request change occurs.

  By the way, when the starter motor 42 is being driven, noise is superimposed on the detection signals of the crank angle sensor 21 and the cam angle sensor 22 due to a large current flowing through the starter motor 42. Therefore, a starter mask process is performed in which the above-described cylinder discrimination process is stopped during a period in which the noise is superimposed (starter mask period). This starter mask period is set to a period from when the starter motor is driven until a predetermined time (for example, 50 ms) elapses. The ECU 10 when performing the mask processing corresponds to “starter mask means”.

  Then, the cylinder discrimination process is started when the starter mask period ends. As described above, in order to perform cylinder discrimination based on the reference position signal and the cylinder discrimination signal, the crankshaft 31 needs to be rotated by a predetermined angle or more. Therefore, when the engine 30 is started, the NE calculation process, the cylinder discrimination process, and the crank period after the starter mask period elapses and until the discrimination period necessary for cylinder discrimination thereafter (cylinder non-discrimination period) is reached. It is in a state where the processing result by the corner calculation processing cannot be acquired. Therefore, the ignition timing control and the fuel injection control, which are performed based on the crank angle and NE, cannot be performed in the cylinder non-discrimination period.

  3 and 4 are time charts for the case where the NE at the time when the request change occurs is a standby area. FIG. 3 shows a case where the stand-by described above is not carried out against the present embodiment, and the asynchronous injection and the drive of the starter motor 42 are carried out simultaneously with the occurrence of the request change. On the other hand, FIG. 4 shows a case where the asynchronous injection and the starter motor 42 are driven when NE is lowered to the threshold value Nth without waiting for the asynchronous injection when the request change occurs.

  First, problems that occur when the standby is not performed as shown in FIG. 3 will be described.

  In the example of FIG. 3, at the time t10 when the request change occurs, the starter motor 42 of the starter 40 starts to be driven and asynchronous injection is performed (see FIG. 3 (b)) in order to perform the advance control. The # 1 cylinder has the earliest timing for the fuel to flow into the combustion chamber 30a and flows during the intake stroke indicated by reference numeral i1. Therefore, the # 1 cylinder is required to ignite the fuel injected asynchronously at the time point i1 at the time point ts.

  However, since the starter mask process is started from time t10 when the starter motor 42 is started to be driven (see FIG. 3C), the mask periods t10 to t20 (50 ms in the example of FIG. 3) and the determination periods t20 to t21 are included. In the cylinder non-discrimination periods t10 to t21, the processing results obtained by the cylinder discrimination processing and the crank angle calculation processing cannot be acquired (see FIG. 3D). As a result, there arises a problem that the # 1 cylinder cannot be ignited at time ts.

  Incidentally, since the reference position signal and the cylinder discrimination signal are output every time they pass TDC, the timing at which the cylinder discrimination processing and the crank angle calculation processing are completed coincides with TDC. Further, in order to determine the cylinder, it is necessary to elapse TDC after the crankshaft 31 rotates by a predetermined angle (for example, 60 deg) or more. Therefore, in the example of FIG. 3, the cylinder discrimination is completed at time t21 of TDC when three strokes have elapsed since the request change has occurred, including the stroke at time t10 when the request change has occurred. In other words, the cylinder non-discrimination period t10 to t21 includes the stroke at time t10 when the request change occurs, and the TDC after the third stroke has elapsed since the request change occurred.

  Next, the reason why the above problem is solved by performing the standby as shown in FIG. 4 will be described.

  In the example of FIG. 4, NE at time t10 when the request change occurs is in the standby region (Nth <NE ≦ N1). Therefore, asynchronous injection and driving of the starter motor 42 are not performed at time t10, and NE is Nth. Asynchronous injection and drive of the starter motor 42 are put on standby until they are lowered (see FIGS. 4A and 4B). Asynchronous injection is performed at time t11 when NE drops to Nth, and at the same time, the starter motor 42 starts to be driven.

  The asynchronously injected fuel flows into the combustion chamber 30a at the earliest timing in the # 4 cylinder, and flows in during the intake stroke indicated by reference numeral i4. Therefore, the # 4 cylinder is required to ignite the fuel injected asynchronously at time i4 at time ts.

  Here, as the engine rotational speed NE in the mask period is lower, the amount of rotation of the crankshaft 31 during the mask period t11 to t20 (50 ms) decreases, and therefore proceeds to the mask period t11 to t20. The number of strokes in the combustion cycle decreases. This means that the cylinder non-discrimination periods t10 to t21 become shorter as the NE at the start time of the starter mask is lower. Therefore, the mask start time t11 in the case of FIG. 4 in which the standby is performed is later than the mask start time t10 in the case of FIG. 3 in which the standby is not performed, but the timing t21 at which the cylinder non-discrimination period ends is the same. It has become.

  Therefore, in the # 4 cylinder that needs to be ignited first, the cylinder discrimination can be ended at the time ts, compared with the request that the fuel injected asynchronously at the time i4 is ignited at the time ts. It is possible to ignite at time ts so as to satisfy.

  The end point t11 of the standby period according to FIG. 4, that is, the point at which driving of the starter motor 42 is started and the point at which asynchronous injection is performed is determined by the threshold value Nth. Therefore, in the present embodiment, the threshold value Nth is set so that the cylinder non-discrimination periods t11 to t21 are equal to or less than two of the four strokes of the combustion cycle including the stroke at time t10 when the request change occurs.

  Next, a restart control processing procedure executed by the microcomputer of the ECU 10 when the above request change occurs will be described with reference to the flowchart of FIG. The process is triggered by the occurrence of a request change such that a restart request is generated during a rotation descent period in which the engine rotation speed NE decreases due to the automatic stop of the engine 30, and is repeatedly executed at a predetermined cycle. For example, it may be executed in a cycle synchronized with the angle signal output from the crank angle sensor 21 or may be executed in a calculation cycle of the microcomputer.

  First, in step S10 shown in FIG. 5, the engine speed NE at the time of request change occurrence is read. This reading may be read in synchronization with the angle signal or may be read in synchronization with the elapsed time.

  In a succeeding step S11, it is determined whether or not the autonomous return by the autonomous return control is possible. Specifically, it is determined whether or not the engine rotational speed NE read in step S10 is equal to or higher than the first rotational speed N1. If it is determined that NE ≧ N1 and autonomous return is possible (S11: NO), asynchronous injection is performed in the subsequent step S12 to perform autonomous return control. That is, asynchronous injection is performed when the request change occurs, and the starter 40 is not driven.

  On the other hand, if it is determined that NE <N1 and the autonomous return is not possible (S11: YES), in the next step S13, it is determined whether restart by the advance control is possible. Specifically, it is determined whether or not the engine rotational speed NE read in step S10 is equal to or higher than the second rotational speed N2.

  If it is determined that NE <N2 and restart by the advance control is not possible (S13: YES), asynchronous injection is performed in the subsequent step S14, and the starter motor 42 is driven in the subsequent step S15. Perform first-out control. That is, asynchronous injection is performed at the time of the request change, and the electromagnetic actuator 43 of the starter 40 is driven to mesh the pinion 41 with the ring gear 31a.

  On the other hand, if it is determined that NE ≧ N2 and restart by the forward control is possible (S13: NO), in the subsequent step S16 (determination means), the engine speed NE read in step S10 is greater than the threshold value Nth. Determine whether the speed is low. If it is determined that NE ≧ Nth (S16: NO), the system waits without executing any of the autonomous return control, the advance control, and the advance control until the NE at the time of the request change occurrence falls to the threshold value Nth. To do. If it is determined that NE <Nth (S16: YES), asynchronous injection is performed in subsequent step S17, and the starter motor 42 is driven in subsequent step S18 to perform forward control.

  In other words, if Nth ≦ NE <N1 at the time of the request change occurrence, the system waits without performing the restart control, performs asynchronous injection when E drops to the threshold value Nth, and sets the starter motor 42. The rotation of the pinion 41 is started by driving. If N2 ≦ NE ≦ Nth at the time of the request change occurrence, asynchronous injection is performed at the time of the request change occurrence, and driving of the starter motor 42 is started.

  Note that after the restart control shown in FIG. 5 is performed, the ignition device 37 is operated by the ignition control described above, but the first ignition after the request change occurs is the same as the end of the cylinder non-discrimination process. It is carried out at (time t21), and the ignition timing thereafter is controlled based on the angle signal or the like so as to approach the optimum ignition timing MBT as described above. Further, when starting or automatically restarting in a state where NE is zero, control is performed so that ignition is performed at a preset timing (for example, BTDC 10 deg) as described above.

  As described above, according to the present embodiment, when the engine speed NE at the time of changing the request cannot be autonomously restored, the engine speed NE is reduced to the threshold value Nth even if the advance control is possible. Waiting (waiting) starts asynchronous injection and driving of the starter motor 42 (advance control is started). Therefore, the cylinder non-discrimination periods T11 to t21 caused by the drive of the starter motor 42 can be ended by the time ts at which the asynchronously injected fuel is desired to be ignited. Therefore, it is possible to improve exhaust emission and drivability.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In the above-described embodiment, the threshold value Nth used for determining the end of the standby period is fixed to a preset value. However, the threshold value Nth may be variably set according to the operating state of the engine 30. Good.

  For example, when the NE descent speed at the time of the request change is high, or when the friction loss is increased due to the low temperature of the engine 30 and the high viscosity of the lubricating oil, the NE at the time of the request change is generated. Is the same, the amount of rotation of the crankshaft 31 during the mask period (for example, 50 ms) is reduced. Therefore, the possibility that the cylinder non-discrimination period becomes longer over three strokes is reduced. Therefore, it is desirable to variably set the threshold value Nth to be higher as the NE descending speed at the time of request change is higher or the engine temperature is lower.

  In the above embodiment, the restart control means (S12), the advance control means (S18), and the advance control means (S15) are provided as restart control means when changing the request. May be abolished. In this case, if the NE at the time of changing the request is in the first rotation speed region, the control is performed after waiting for the NE to fall to the threshold value Nth.

  In the above embodiment, when the NE at the time of changing the request is in the standby area, the starter motor 42 starts to be driven when the NE drops to Nth, and asynchronous injection is also performed. Asynchronous injection does not need to be performed simultaneously with the drive of the starter motor 42 and may be after the start of the drive of the starter motor 42. However, if the execution timing of the asynchronous injection is too late, the ts time point at which ignition of the asynchronously injected fuel is required becomes excessively later than the end time point of the cylinder non-discrimination periods T11 to t21, and the automatic restart is quickly performed. Will prevent you from completing it. Therefore, it is desirable that the asynchronous injection be performed at a timing such that the time ts at which ignition with respect to the asynchronously injected fuel is required coincides with the end time of the cylinder non-discrimination periods T11 to t21.

  In the above embodiment, the cam angle sensor 22 is used as a cylinder discrimination sensor that outputs a cylinder discrimination signal (detection signal). However, any sensor that outputs a signal associated with four strokes of one combustion cycle may be used. The cylinder discrimination sensor of the present invention is not limited to the cam angle sensor 22.

  The threshold value Nth is desirably set to a value lower than the rotation speed when the engine 30 is idling. The threshold value Nth is preferably set to a value greater than zero. In the above embodiment, the threshold value Nth is set to a value higher than the second rotational speed N2, but the threshold value Nth may be set to a value lower than the second rotational speed N2.

  In each of the above embodiments, the engine rotational speed NE is calculated based on the detected value of the crank angle sensor 21, the NE calculated in this way is compared with the threshold value Nth, and the end of the waiting period for the advance control is determined. Yes. On the other hand, the intake air amount and the intake pressure calculated based on the detection value of the air flow meter 24 may be substituted for the NE used for the determination.

  For example, when a determination threshold value (intake pressure threshold value or intake pressure threshold value) corresponding to the intake pressure or intake air amount is set, and intake pressure> intake air pressure threshold, NE <threshold value Nth is assumed, and the waiting period You may determine with completion. Alternatively, when the intake air amount <the threshold value for the intake air amount, NE <threshold value Nth may be considered and the end of the standby period may be determined.

  DESCRIPTION OF SYMBOLS 10 ... ECU (cylinder discrimination | determination means, starter mask means, request change time control means), 21 ... Crank angle sensor (cylinder discrimination sensor), 22 ... Cam angle sensor (cylinder discrimination sensor), Nth ... Threshold, S16 ... Determination means , T11 to t20 ... starter mask period, t20 to t21 ... discrimination period, t11 to t21 ... cylinder non-discrimination period.

Claims (5)

An internal combustion engine that sequentially performs four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke in a cylinder, and is applied to an internal combustion engine having an idle stop function of automatic stop and automatic restart,
Cylinder discrimination means for discriminating which of the four strokes is a stroke performed in the cylinder based on a detection signal output from a cylinder discrimination sensor;
A period in which noise is superimposed on the detection signal due to driving of a starter motor that applies a rotational driving force to the crankshaft of the internal combustion engine is set as a starter mask period, and in the starter mask period, the cylinder discrimination means A starter mask means for canceling discrimination;
When there is a request change such as a request for the automatic restart during a rotation descent period in which the fuel injection is cut and the engine rotation speed is lowered in response to the generation of the automatic stop request, the engine rotation speed is A request changing control means for driving and restarting the starter motor without waiting for it to drop to zero;
With
A period including the starter mask period set by driving the starter motor with the occurrence of the request change, and a determination period required for the determination by the cylinder determination unit after the starter mask period ends. When the cylinder non-discrimination period during which the discrimination result by the cylinder discrimination means cannot be obtained,
The starter motor is driven by the request change time control means on condition that the engine rotational speed is reduced to a speed at which the cylinder non-discrimination period is equal to or less than two of the four strokes. An idle stop control device characterized by permitting start.   Fuel injection by the request change time control means is permitted on condition that the engine rotational speed is reduced to a speed at which the cylinder non-discrimination period is equal to or less than two of the four strokes. The idle stop control device according to claim 1. An internal combustion engine that sequentially performs four strokes of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke in a cylinder, and is applied to an internal combustion engine having an idle stop function of automatic stop and automatic restart,
Cylinder discrimination means for discriminating which of the four strokes is a stroke performed in the cylinder based on a detection signal output from a cylinder discrimination sensor;
A period in which noise is superimposed on the detection signal due to driving of a starter motor that applies a rotational driving force to the crankshaft of the internal combustion engine is set as a starter mask period, and in the starter mask period, the cylinder discrimination means A starter mask means for canceling discrimination;
When there is a request change such as a request for the automatic restart during a rotation descent period in which the fuel injection is cut and the engine rotation speed is lowered in response to the generation of the automatic stop request, the engine rotation speed is A request changing control means for driving and restarting the starter motor without waiting for it to drop to zero;
With
A period including the starter mask period set by driving the starter motor with the occurrence of the request change, and a determination period required for the determination by the cylinder determination unit after the starter mask period ends. When the cylinder non-discrimination period during which the discrimination result by the cylinder discrimination means cannot be obtained,
Fuel injection by the request change time control means is permitted on condition that the engine rotational speed is reduced to a speed at which the cylinder non-discrimination period is equal to or less than two of the four strokes. An idle stop control device characterized by that.   The idle stop control device according to any one of claims 1 to 3, wherein the first ignition after the request change occurs is performed simultaneously with the end of the cylinder non-discrimination period. The request change time control means includes:
A determination unit that determines that the cylinder non-discrimination period is equal to or less than two of the four strokes when the engine speed after the request change occurs is equal to or less than a predetermined threshold;
The idle stop control device according to any one of claims 1 to 4, wherein the threshold value is variably set according to an operating state of the internal combustion engine.

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