JP2011157948A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device, avoiding a state of an excessive fuel amount caused by injection of an injection amount in starting, when an idle stop request is changed. <P>SOLUTION: It is determined that the engine is in a start period when an engine speed NE is determination thresholds TH1a, TH1b, TH2 or lower, and it is determined that the engine has started when the NE is higher than the thresholds (S14, S17). When it is determined that the engine is in the start period, a fuel amount set as an injection amount in starting is injected. When it is determined that the engine has started, a fuel amount based on a reference injection amount according to the NE and an engine load is injected. Further, during an engine speed decreasing period where the NE is decreased caused by cutdown of fuel injection according to an automatic stop request by an idle stop function, the determination thresholds TH1a, TH1b, TH2 are set to be lower than that in normal times other than the rotation decrease period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Patent Document 1 and the like describe a device for controlling the fuel injection amount of an engine (internal combustion engine). In this control device, the injection amount is controlled based on the basic injection amount calculated according to the engine speed and the engine load (for example, the intake air amount). However, if the operating state of the internal combustion engine is during the start-up period, instead of calculating the basic injection amount, an amount of fuel set as the “start-up injection amount” is injected. The method for setting the starting injection amount will be described below.

  At the time of starting the engine, the pressure in the intake port is atmospheric pressure (no negative pressure). Therefore, when the engine is operating and the negative pressure is sufficiently reduced, the intake pressure is increased to the combustion chamber during the start-up period when the negative pressure is higher than the amount of intake air sucked into the combustion chamber in one intake stroke. The amount of inhaled air increases. Therefore, the above-described start-up injection amount is set in anticipation of an increase in the intake air amount during the start-up period.

  In the case of a port-injection gasoline engine that injects fuel into an intake port, part of the injected fuel remains in a liquid state and adheres to the inner wall surface of the intake port (see reference numeral 34a in FIG. 1). After that, it is vaporized and sucked into the combustion chamber. However, since the wet fuel is not yet attached at the time of starting the engine, there is no fuel to be vaporized and sucked after the attachment. Thus, the above-described start-up injection amount is set in anticipation of a shortage of wet fuel during the start-up period.

  In the conventional general injection control device, it is sequentially determined whether or not the engine rotational speed NE has increased to a predetermined determination threshold TH during the start-up period in which the injection control is performed with the start-up injection amount. Then, after it is determined that the determination threshold value TH has been reached, it is assumed that the engine is in the post-start state, and the control is switched to the injection control based on the basic injection amount. That is, a start period determination unit that determines whether the start period or the post-start state is in accordance with whether NE <TH is satisfied, and the content of the injection control is switched according to the determination result.

Japanese Patent Laid-Open No. 10-9016

  Here, in an engine having an idle stop function for automatic stop and automatic restart, a request for automatic restart is made during a rotation descent period in which the fuel injection is cut and the engine rotational speed decreases due to the occurrence of the automatic stop request. May occur. In recent years, restarting such as driving the starter motor without waiting for the engine speed to drop to zero in order to quickly restart when the content of the request for the idle stop function changes in this way. Techniques for performing control have been developed.

  In the case of an engine in which such restart control is employed, if it is attempted to switch the injection control according to the determination result by the start period determination means, the start period is reached when NE is reduced to NE = TH during the rotation decrease period. It is determined that there is, and switching is performed so that the injection control is performed based on the starting injection amount.

  However, the above-described method for setting the injection amount at start-up assumes that the engine is started from a state where the engine speed is zero. That is, as described above, the starting injection amount is set in anticipation of an increase in the intake air amount during the starting period and in anticipation of a shortage of wet fuel. On the other hand, when the engine is restarted while the crankshaft is rotating with the demand for idle stop being changed as described above, the negative pressure has already decreased and the vaporized portion of the wet fuel is combusted. Inhaled into the chamber.

  Therefore, if it is determined that the starting period is reached when NE = TH during the rotational descent period and the injection control is performed with the injection amount at the starting time, an excessive amount of fuel is injected. As a result, there are concerns about the occurrence of a torque step or misfire due to rich air-fuel ratio.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection control that avoids an excessive fuel state caused by injecting a starting injection amount when a request for idling stop changes. To provide an apparatus.

  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, when the engine rotational speed of the internal combustion engine is equal to or less than a predetermined determination threshold value, the start period determination means that determines that the operating state of the internal combustion engine is in the start period, and the start period When it is determined that there is a start-time injection control means for controlling the fuel injection valve to inject the amount of fuel set as the start-time injection amount, and in the post-start state that is determined not to be the start period, And a post-startup injection control means for controlling the fuel injection valve to inject an amount of fuel calculated based on each engine speed and engine load, and the internal combustion engine is an idle stop for automatic stop and automatic restart. It has a function, and during the rotation descent period during which the engine speed is reduced by cutting the fuel injection in response to the occurrence of the automatic stop request, it is compared with the normal time other than the normal rotation descent period. Characterized in that to set lower determination threshold.

  In short, in the above-described invention, the determination threshold value used for determining whether or not it is during the start-up period in which the control by the start-up injection control means (start-up injection control) is performed, Set lower. Therefore, when the engine rotation speed starts to increase with the restart request during the rotation descent period, the opportunity to restart without increasing the engine rotation speed to the determination threshold value increases. In other words, when the request content of the idle stop function is changed, the control by the post-startup injection control means (post-startup injection control) can be continuously performed without performing the start-time injection control.

  Therefore, according to the above-described invention, when the request for idling stop changes, it is possible to avoid an excessive fuel state caused by injecting the injection amount at the time of starting, and to avoid the occurrence of a torque step or misfire due to rich air-fuel ratio. be able to.

  The invention according to claim 2 is characterized in that the determination threshold is set to a higher value as the temperature of the internal combustion engine is lower.

  Here, the lower the temperature of the internal combustion engine, the larger the friction loss of the internal combustion engine due to the reason that the lubricating oil becomes lower temperature and higher viscosity. Then, the speed at which the engine speed decreases is increased. Then, when the post-startup injection is started based on the restart request, the post-startup injection is performed at a lower speed than the assumed engine rotation speed, so there is a concern that the injection amount will be insufficient.

  In the above-mentioned invention in view of this point, since the determination threshold is increased as the internal combustion engine is colder, the above-described concern can be solved. In other words, the higher the temperature of the internal combustion engine is, the lower the determination threshold is, so that it is possible to avoid an unnecessarily increased opportunity for performing the start-up injection control.

  Incidentally, in carrying out the above invention, the temperature of the internal combustion engine may be directly detected, but instead of such detection, the temperature of the engine lubricating oil or the temperature of the engine cooling water is detected, and these temperatures are detected. Alternatively, the temperature may be substituted. Moreover, it can be said that the temperature of the internal combustion engine is lower as the elapsed time from the initial start of the internal combustion engine is shorter. Therefore, as described in claim 3, the determination threshold value may be set to a higher value as the elapsed time from the initial start time of the internal combustion engine is shorter.

  According to a fourth aspect of the present invention, the fuel injection is cut in response to the generation of the automatic stop request and the determination threshold value used when the engine rotational speed decreases is set to zero, and the zero state continues for a predetermined time. Engine start determining means for determining that the internal combustion engine has stopped when the engine speed has fallen below the determination threshold during the rotation descent period. Until the determination is made, the determination that the state is after the start is continued, and the determination is made that the start period is determined when the engine stall determination is made.

  In the case where the engine speed is reduced to the determination threshold value during the rotation descent period and the injection control is performed with the starting injection amount, even if the engine speed is decreased to the determination threshold value, the crankshaft is still slightly rotating. Thus, the actual intake air amount may be smaller than the intake air amount expected for the starting injection amount. Further, due to the remaining wet fuel vaporization, there may be an excess of the shortage of wet fuel expected in the starting injection amount. In other words, it may not be possible to reliably avoid an excessive fuel state caused by injecting the starting injection amount.

  In view of this point, in the above invention, even when the engine speed falls below the determination threshold during the rotation descent period, the engine speed drops to zero, and the zero state continues for a predetermined time. Since it is determined that the engine is in the post-start state until the engine stall is determined, it is possible to reliably avoid an excessive fuel state caused by injecting the start injection amount.

  According to a fifth aspect of the invention, there is provided negative pressure determining means for determining whether or not a high negative pressure state in which the negative pressure generated in the intake pipe is equal to or higher than a predetermined value, and the start period determining means includes the rotation period. When the engine rotational speed becomes equal to or lower than the determination threshold value during the descent period, the determination that the engine is in the post-start state is continued until the high negative pressure state is subsequently determined. It is characterized by switching to the determination that it is the starting period at the time of determination.

  In the case where the engine speed is reduced to the determination threshold value during the rotation descent period and the injection control is performed with the starting injection amount, even if the engine speed is decreased to the determination threshold value, the crankshaft is still slightly rotating. In some cases, the pressure in the intake port does not increase to atmospheric pressure, and a slight negative pressure is generated. Then, the actual intake air amount becomes smaller than the intake air amount expected for the start-time injection amount, and as a result, an excessive fuel state due to the injection of the start-time injection amount cannot be avoided.

  In view of this point, in the above-described invention, even when the engine rotational speed becomes equal to or lower than the determination threshold during the rotation descent period, it is determined as a high negative pressure state in which the negative pressure generated in the intake pipe is equal to or higher than a predetermined value. Since the determination that the engine is in the post-start state is continued until the start is made, it is possible to reliably avoid an excessive fuel state caused by injecting the injection amount at the start.

  According to a sixth aspect of the present invention, there is provided an intake air determination means for determining whether or not the intake air flow rate is a small intake state (including a state where the intake air flow rate is zero) in which the intake air flow rate is equal to or less than a predetermined value. When the engine rotational speed becomes equal to or lower than the determination threshold value during the rotation descent period, the means continues to determine that the engine is in the post-start state until the low intake state is determined. Switching to the determination that the engine is in the starting period when it is determined that the intake state has occurred.

  As described above, even if the threshold value is reduced to the determination threshold, the actual intake air amount may be smaller than the intake air amount expected for the start-time injection amount. There are cases where the situation cannot be avoided.

  In view of this point, in the above-described invention, even when the engine rotational speed becomes equal to or lower than the determination threshold value during the rotation descent period, the engine is started until it is determined that the intake air flow rate is equal to or less than the predetermined value. Since the determination that the state is the rear state is continued, it is possible to reliably avoid an excessive fuel state caused by injecting the starting injection amount.

The figure explaining the hardware constitutions of an internal-combustion engine to which the fuel injection control device concerning a 1st embodiment of the present invention is applied. The figure which shows the time change of the engine speed NE at the time of starting an engine from the state of NE = 0. 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 left column in the figure is an example when the present invention is not used, and the right column in the figure is a time chart showing an example when the present invention is used. The flowchart which shows the process sequence of the determination after starting by 1st Embodiment. The flowchart which shows the process sequence of the determination after starting by 2nd Embodiment of this invention. The flowchart which shows the process sequence of the determination after starting by 3rd Embodiment of this invention. The flowchart which shows the process sequence of the determination after starting by 4th Embodiment of this invention.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
The internal combustion engine control apparatus according to this embodiment is intended for a reciprocating engine (internal combustion engine) for a four-wheeled vehicle, and the engine is an ignition type gasoline engine using regular fuel as gasoline.

  FIG. 1 is a diagram showing a hardware configuration of an engine. Detection signals from various sensors such as a crank angle sensor 21, a cooling water temperature sensor 22, an intake pressure sensor 23, and an air flow meter 24 are included in an electronic control unit (ECU 10). Is entered.

  The crank angle sensor 21 detects the rotational speed (engine rotational speed NE) of the crankshaft 31 (output shaft) of the engine 30. The coolant temperature sensor 22 detects the temperature of the engine coolant. The intake pressure sensor 23 detects the pressure (negative pressure) in the intake pipe 34. 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 controls the injection amount and 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, intake pressure or 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.

  Next, the control of the fuel injection amount 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).

  Then, according to the operating state of the engine 30, the fuel for the warm-up increase and the acceleration increase is calculated, and the target injection amount is calculated by adding the warm-air increase and the acceleration increase to the basic injection amount. The “warm-up increase” is to increase the temperature of the engine 30 by increasing the amount of fuel during the warm-up period of the engine 30, and the “acceleration increase” is to rapidly increase the accelerator pedal. The output torque is immediately increased when acceleration of a predetermined amount or more is required, such as when the vehicle is stepped on.

  However, if the operating state of the engine 30 is during the start-up period, the intake air amount is unstable, and the reliability of the detection values of the air flow meter 24 and the intake pressure sensor 23 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.

  In short, the ECU 10 determines whether it is the start period or after the start period has elapsed (after the start). When it is determined that the start period is reached, the ECU 10 performs injection control based on the start injection amount, and starts When it is determined to be later, injection control is performed based on the basic injection amount.

  Note that the starting injection amount may be variably set according to the engine coolant temperature detected by the coolant temperature sensor 22. For example, the starting injection amount may be reduced as the coolant temperature increases. Incidentally, when the engine 30 has a plurality of cylinders, asynchronous injection is performed in which fuel is simultaneously injected from the fuel injection valve 33 provided in each cylinder when injection is performed at the starting injection amount.

  FIG. 2 is a diagram showing a time change of the engine speed NE when the engine 30 is started from a state where NE = 0. First, the starter 40 (see FIG. 1) is activated at time t1. Specifically, the pinion 41 (see FIG. 1) of the starter 40 is meshed with a ring gear 31a attached to the crankshaft 31. Thereby, NE rises from time t1. Thereafter, at time t2, the peripheral speed of the ring gear 31a becomes faster than the peripheral speed of the pinion 41, and the cranking period ends. Thereafter, complete combustion (combustion state in which the air-fuel mixture sucked into the combustion chamber 30a is completely combusted) occurs at time t3, and NE further increases. Then, it is determined that the start period has ended at time t4 when the determination threshold TH1a (for example, 400 rpm) is exceeded.

  That is, it is determined that the starting period is from the time point t1 to the time point t4, and fuel injection is performed at the starting injection amount (starting injection). Based on the fuel injection (post-startup injection).

  However, since the combustion state is unstable immediately after the time point t3 when the complete combustion is performed, the NE may temporarily drop as indicated by the symbol P. In this case, if the determination threshold value TH1a is set to 400 rpm, it is determined again that the engine is in the start period due to the temporary drop, and injection at the start is performed. Accordingly, the determination threshold is provided with hysteresis, and the determination threshold is set to TH1a when NE rises, and is set to a value TH1b (for example, 300 rpm) lower than that when rising.

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

  The starter 40 is a so-called pinion push-out starter, and includes a motor 42, a pinion 41 that is rotationally driven by the motor 42, an electromagnetic actuator 43 that pushes the pinion 41, and the like. 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 the ECU 10 controlling the energization of the motor 42 to be turned on.

  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 the request content of the idle stop function is changed so that the restart request is generated during the rotation descent period in which the engine rotation speed NE is decreased by the automatic stop of the engine 30, the engine 30 should be restarted quickly. The restart control for driving the starter 40 is performed without waiting for NE to drop to zero. However, the content of the restart control changes as shown in FIG. 3 according to the timing at which the restart request is generated during the rotation descent period.

<Autonomous return control>
When an engine restart request is generated in a first rotational speed region where NE is higher than a first rotational speed N1 (for example, 500 rpm) during a rotational speed reduction period in which the engine rotational speed NE is reduced due to the automatic stop of the engine 30, 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>
When the engine restart request is generated in the second rotation speed region where NE is equal to or lower than the first rotation speed N1 and higher than the second rotation speed N2 (for example, 250 rpm) during the rotation descent period, the rotation of the ring gear 31a is performed. Since the speed is relatively high, it is determined that the pinion 41 cannot be smoothly meshed with the ring gear 31a unless the rotation speed of the pinion 41 is synchronized with the rotation speed of the ring gear 31a, and the advance control is executed. In this advance control, the rotational speed of the pinion 41 is synchronized with the rotational speed of the ring gear 31a by the motor 42 to reduce the difference between the rotational speeds of the two, and then the pinion 41 is meshed with the ring gear 31a by the electromagnetic actuator 43. Cranking is started and the engine 30 is restarted.

<First-out control>
When the engine restart request is generated in the third rotation speed region where NE is equal to or less than the second rotation speed N2 during the rotation descent period, the rotation speed of the pinion 41 is reduced because the rotation 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 with the rotational speed of the ring gear 31a, and the advance control is executed. 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 pinion 41 is rotated by the motor 42 and cranking by the starter 40 is started to restart the engine 30. .

  FIG. 4 shows an example of a case where a restart request is generated at time t10 during a rotation descent period in which the fuel injection amount is set to zero (fuel cut) and the engine rotation speed NE is reduced by the automatic stop of the engine 30. In this case, at the time point t10, any one of the above-described autonomous return control, advance control, and advance control is performed, so that the engine 30 is restarted while NE is descending, so that NE becomes zero. It starts to rise in the middle of the rotation descent without reaching (see FIG. 4A).

  However, in this case, if the determination threshold value TH1a, TH1b is used as it is, it is determined whether or not the engine is in the starting period, and based on the determination result, the control based on the starting injection amount and the control based on the basic injection amount are switched. As shown in the left column of FIG.

  That is, before NE starts to rise due to restart, it falls to the determination threshold value TH1b or less, so that at the time t20 when NE = TH1b, the determination after the start is switched to the determination with the start period. At time t30 when NE = TH1a ascending and switching to start-up determination, refer to the left column in FIG. 4 (b). As a result, the fuel injection cut state is switched to the injection state based on the basic injection amount at time t10. However, since it switches to determination that it is a starting period after that at t20 time, it switches to the injection state based on the injection quantity at the time of starting. Then, at the time of t30, the engine state is switched to the injection state based on the basic injection amount as it is switched to the determination that the engine is started.

  Since the starting injection amount is set on the assumption that the engine is started from a state where NE is zero, if the starting injection amount of fuel is injected with the crankshaft 31 rotating to some extent, the injection amount becomes excessive, There are concerns about problems such as generation of torque steps and misfire due to rich air-fuel ratio.

  Therefore, in the present embodiment, the fuel injection is cut in response to the occurrence of a request for automatic stop, and it is used to determine whether or not the engine is in the starting period during the rotation descent period during which the engine speed NE decreases (see FIG. 4A). The determination threshold value TH2 is set to be lower than the determination threshold values TH1a and TH1b at the normal time (see FIG. 2) other than the rotation descent period (see the right column of FIG. 4A).

  As a result, the NE does not fall below the determination threshold value TH2 before it starts to rise due to the restart, so that the start is not switched to the determination of the start period after the restart request t10 is made. The determination that it is later is continued (see the right column of FIG. 4B). Therefore, at time t10 when the restart request is generated, after switching from the fuel injection cut state to the injection state based on the basic injection amount, the injection with the basic injection amount is continued without switching to the injection state based on the start-up injection amount. (See the right column in FIG. 4 (d)). Therefore, the above-mentioned concerns such as generation of a torque step or misfire caused by injecting fuel at the starting injection amount can be solved.

  Note that when starting from a state where NE is zero, the intake pressure sensor 23 and the air flow meter 24 cannot acquire the intake pressure and the intake air amount, whereas the crankshaft 31 rotates as shown in FIG. In the case where the engine is restarted during operation, the intake pressure or the intake air amount can be acquired. Therefore, the opening degree of the throttle valve 35 can be controlled so that the intake amount according to the engine load is obtained. Therefore, in the right column of FIG. 4 showing the present embodiment, the intake air amount after t10 is controlled to gradually increase (see FIG. 4C). Then, the injection amount is controlled to gradually increase so that the injection amount is commensurate with the intake amount (see FIG. 4D).

  Further, when starting from a state where NE is zero, it is necessary to rotate the crankshaft 31 by a predetermined angle in order to calculate NE based on the detection value of the crank angle sensor 21, so that NE should be grasped immediately. I can't. Further, since the crankshaft 31 needs to rotate by a predetermined angle in order to calculate the crank angle based on the detection value of a cam angle sensor (not shown), the crank angle cannot be grasped immediately. Therefore, the injection control based on the basic injection amount cannot be performed immediately.

  On the other hand, when restarting while the crankshaft 31 is rotating as shown in FIG. 4, the NE at the time of switching from the fuel cut state to the state where the injection is started can be acquired. Therefore, the basic injection amount can be calculated, and the injection control based on the basic injection amount can be performed.

  FIG. 5 is a flowchart showing a processing procedure for the determination after starting by the microcomputer of the ECU 10, and the processing is repeatedly executed at a predetermined cycle.

  First, in step S10 shown in FIG. 5, the engine speed NE and the engine coolant temperature (water temperature) calculated based on the detected values of the crank angle sensor 21 and the coolant temperature sensor 22 are acquired.

  In a succeeding step S11, it is determined whether or not an automatic stop request is generated by the idle stop function and NE> 0. In short, it is determined whether or not it is during the rotation descent period in which the engine rotation speed NE drops due to the automatic stop of the engine 30. If it is determined that the rotation descent period is in progress (S11: YES), the process proceeds to step S12, and it is determined whether or not the fuel injection is cut off when the automatic stop request is generated.

  If it is determined that the injection is being cut (S12: YES), the process proceeds to step S13, and the determination threshold value TH2 is calculated based on the water temperature acquired in step S10. For example, the optimum value of the determination threshold value TH2 for the water temperature is acquired in advance by a test, the relationship between the optimum value and the water temperature is stored as a map M1 (see FIG. 5), and the determination threshold value TH2 is used using the map M1. What is necessary is just to calculate the optimal value. The determination threshold TH2 is set to a higher value as the water temperature is lower. However, the maximum value of the determination threshold value TH2 is set to be a value smaller than the determination threshold value TH1b used during NE descent among the determination threshold values used in the normal state shown in FIG.

  In subsequent steps S14 to S15, it is determined whether the engine is in the start period or after the start using the determination threshold value TH2 calculated in step S13. That is, in step S14 (starting period determination means), if it is determined that NE acquired in step S10 is larger than determination threshold TH2 (S14: YES), it is determined in the subsequent step S15 that “after starting” and NE> If it is determined that it is not TH2 (S14: NO), it is determined as the “starting period” in the subsequent step S16.

  On the other hand, when it is determined in the previous step S11 that the engine speed NE is not decreasing due to the automatic stop (S11: NO), or when it is determined that the injection is not being cut (S12: NO). 2 is considered to be the normal time shown in FIG. 2 and is the start period or after the start using the determination threshold values TH1a and TH1b set higher than the determination threshold value TH2 calculated in step S13. Determine. That is, if it is determined in step S17 (starting period determining means) that NE> TH1a, TH1b (S17: YES), it is determined in the previous step S15 that “after starting”, and NE> TH1a, TH1b is not satisfied. If it is determined (S17: NO), it is determined as the “starting period” in the previous step S16.

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

  (1) According to the present embodiment, the determination threshold value used for determining whether or not it is during the start-up period in which the start-time injection control is performed is set lower than during normal rotation during the rotation descent period due to automatic stop. (TH2 <TH1b). Therefore, when the engine rotation speed NE starts to increase with the restart request during the rotation lowering period, the opportunity for restarting without increasing NE to the determination threshold TH2 increases.

  Therefore, when the content of the idle stop request changes (Change of Mind), it is possible to avoid an excessive fuel state by injecting the injection amount at the time of starting, and to avoid misfiring due to generation of a torque step or rich air-fuel ratio. be able to.

  (2) Further, when the content of the idle stop request changes as described above, even if NE falls to the determination threshold TH2 and is determined as the “starting period”, the determination threshold is set so that TH2 <TH1b. Since it is set, the NE at the time when it is determined as the start period becomes low. Therefore, since NE at the time of starting the injection control at the start becomes low, the intake pressure at the start time of the start-up injection control becomes higher than when the determination threshold value is made the same as the normal time. The amount of intake air increases. Further, the amount of vaporized wet fuel that is sucked into the combustion chamber 30a at the start of start-up injection control is smaller than when the determination threshold is the same as in the normal state.

  Therefore, if the idle stop request changes, even if NE falls to the determination threshold TH2 and is determined to be the “starting period”, an excessive fuel state caused by injecting the starting injection amount is suppressed. it can.

  (3) The lower the temperature of the engine 30, the lower the temperature of the lubricating oil and the higher the viscosity, so the friction loss of the engine 30 increases. Then, the NE descending speed when the NE descends due to the automatic stop increases. Then, at the time of starting post-start injection based on the restart request, post-start injection is performed in a state of lower rotation than the assumed NE, and there is a concern that the injection amount will be insufficient. On the other hand, in the present embodiment, the determination threshold TH2 is increased as the water temperature is lower (see S13 in FIG. 5), and thus the above-mentioned concern can be solved.

(Second Embodiment)
In the first embodiment, the determination threshold value TH2 is variably set according to the temperature of the engine coolant. In the present embodiment shown in FIG. 6, the determination threshold value is determined according to the elapsed time from the initial start of the engine 30. TH2 is variably set. Hereinafter, the processing content of FIG. 6 is demonstrated centering on the difference with FIG. The hardware configuration of the engine in this embodiment is the same as that of the first embodiment shown in FIG.

  First, in step S20 shown in FIG. 6, the engine rotational speed NE is acquired in the same manner as in S10, and the elapsed time from the initial start time when the occupant turns on the ignition switch to start the engine 30 is acquired. .

  In the subsequent step S21, as in S11, it is determined whether or not it is during a rotation descent period in which the engine rotation speed NE decreases due to the automatic stop of the engine 30. Further, in the subsequent step S22, it is determined whether or not the fuel injection has been cut off as the automatic stop request is generated in the same manner as in S12.

  If it is determined that the injection is being cut during the rotation descent period (S21: YES, S22: YES), the process proceeds to step S23, and the determination threshold is based on the elapsed time from the initial start acquired in step S20. TH2 is calculated. For example, the optimal value of the determination threshold value TH2 for the elapsed time is acquired in advance by a test, the relationship between the optimal value and the elapsed time is stored as a map M2 (see FIG. 6), and the determination is performed using the map M2. What is necessary is just to calculate the optimal value of threshold value TH2. Note that the determination threshold value TH2 is set to a higher value as the elapsed time is shorter. However, the maximum value of the determination threshold value TH2 is set to be a value smaller than the determination threshold value TH1b used during NE descent among the determination threshold values used in the normal state shown in FIG.

  In subsequent step S24 (starting period determining means), if it is determined that NE acquired in step S10 is larger than determination threshold TH2 (S24: YES), it is determined as “after start” in subsequent step S25. If it is determined that it is not> TH2 (S24: NO), it is determined as the “starting period” in the subsequent step S26.

  On the other hand, if a negative determination is made in the previous step S21 or step S22, the determination threshold value is set to a value higher than the determination threshold value TH2 calculated in step S23, assuming that the normal time shown in FIG. Using TH1a and TH1b, it is determined whether it is the starting period or after the starting. That is, in step S27 (starting period determining means), if it is determined that NE> TH1a, TH1b (S27: YES), “after starting” is determined (S25), and NE> TH1a, TH1b is not determined. (S27: NO), it is determined as the “starting period” (S26).

  Also in the present embodiment described in detail above, the determination threshold value used for determining whether or not it is during the start period in which the start time injection control is performed is set to be lower than the normal time during the rotation descent period due to the automatic stop. (TH2 <TH1b), the same effects as the above (1) and (2) according to the first embodiment can be obtained.

  Further, the shorter the elapsed time from the initial start of the engine 30, the lower the temperature of the engine coolant and the greater the friction loss of the engine 30. Therefore, the effect similar to the above (3) according to the first embodiment can be obtained also by the present embodiment in which the determination threshold value TH2 is set higher as the elapsed time from the initial start time is shorter.

(Third embodiment)
In the present embodiment shown in FIG. 7, even if NE becomes equal to or less than the determination threshold value TH2 (TH2 = 0) during the NE rotation descent period accompanying the generation of an automatic stop request, the engine stall determination is made thereafter. Until it is determined that the engine is in the post-start state, the engine is switched to the start period when the engine stall determination is made. Hereinafter, the processing content of FIG. 7 will be described focusing on differences from FIG. The hardware configuration of the engine in this embodiment is the same as that of the first embodiment shown in FIG.

  First, in step S30 shown in FIG. 7, the engine speed NE is acquired in the same manner as in S10. In the subsequent step S31, similarly to S11, it is determined whether or not the engine 30 is in a rotation descent period in which the fuel injection is cut by the automatic stop and the engine rotation speed NE decreases. And if it determines with it being during the said rotation fall period (S31: YES), it will progress to step S33 and will perform the engine stall determination demonstrated below.

  That is, in the present embodiment, the determination threshold value TH2 is set to zero, and NE = 0 when NE drops to zero with the occurrence of an automatic stop request (that is, when NE = TH2). The time for which the state of NE = 0 is continued from this point is measured. Then, in the subsequent step S34 (engine stop determination means (start period determination means)), if the duration measured in step S33 has reached a predetermined time, it is determined that the engine is in an engine stall state where the engine is completely stopped. To do.

  If the engine stall is determined (S33: YES), it is determined as the “starting period” in the following step S36. If the engine stall is not determined (S33: NO), in the subsequent step S25, “after start-up” is determined. Is determined. In short, even if NE falls to zero due to automatic stop, when NE = 0, it is not determined as the starting period, and then the state of NE = 0 is continuously determined for a predetermined time. At the time, the determination “after start” is switched to the determination “start period”.

  If a negative determination is made in the previous step S31, the normal time shown in FIG. 2 is considered, and it is determined using the determination thresholds TH1a and TH1b whether the engine is in the start period or after the start. That is, in step S37 (starting period determining means), if it is determined that NE> TH1a, TH1b (S37: YES), “after starting” is determined (S35), and it is determined that NE> TH1a, TH1b is not satisfied. (S37: NO), it is determined as the “starting period” (S36).

  Also in the present embodiment described in detail above, the determination threshold value used for determining whether or not it is during the start period in which the start time injection control is performed is set to be lower than the normal time during the rotation descent period due to the automatic stop. (TH2 <TH1b), the same effects as the above (1) and (2) according to the first embodiment can be obtained.

  By the way, in the case where NE is lowered to zero due to the automatic stop and the injection control is performed at the starting injection amount, even when NE = 0, the crankshaft 31 is not changed when NE = 0. In some cases, the engine is still rotating slightly. In this case, the actual intake air amount is smaller than the intake air amount expected for the start-up injection amount. Further, due to the remaining wet fuel vaporization, there may be an excess of the shortage of wet fuel expected in the starting injection amount. That is, if the injection amount at the start is injected immediately after NE = 0, there is a concern that an excessive fuel state cannot be avoided reliably.

  In view of this point, in the present embodiment, even if NE drops due to automatic stop and becomes zero, the state of NE = 0 is continuously determined for a predetermined time, and when the engine stall determination is made, The determination is switched to the determination of “starting period”. Therefore, since it is avoided that the injection amount at the start is immediately decreased after NE = 0, the above-mentioned concern can be solved.

(Fourth embodiment)
In the present embodiment shown in FIG. 8, even if NE becomes equal to or less than the determination threshold TH2 during the NE rotation descent period accompanying the generation of an automatic stop request, the intake pressure (the negative pressure in the intake pipe 34) is thereafter increased. ) Continues to be determined to be in the post-start state until the value becomes equal to or greater than a predetermined value, or until the intake air amount becomes equal to or less than a predetermined value. Then, when the intake pressure increases and reaches a predetermined value, or when the intake amount decreases and reaches a predetermined value, the determination is made that the engine is in the starting period. Hereinafter, the processing content of FIG. 8 is demonstrated centering on the difference with FIG. The hardware configuration of the engine in this embodiment is the same as that of the first embodiment shown in FIG.

  First, in step S40 shown in FIG. 8, the engine rotational speed NE and the water temperature are acquired in the same manner as in S10, and the intake pressure (negative pressure) detected by the intake pressure sensor 23 or the air flow meter 24 is detected. Get the intake volume.

  In the subsequent step S41, as in S11, it is determined whether or not it is during a rotation descent period in which the engine rotation speed NE decreases due to the automatic stop of the engine 30. Further, in the subsequent step S42, it is determined whether or not the fuel injection has been cut off as the automatic stop request is generated, as in S12. If it is determined that the injection is being cut during the rotation descent period (S41: YES, S42: YES), the process proceeds to step S43, and the determination threshold TH2 is calculated based on the water temperature in the same manner as S13.

  In subsequent step S44 (starting period determining means), if it is determined that NE acquired in step S10 is larger than determination threshold TH2 (S44: YES), it is determined as “after starting” in subsequent step S45. If it is determined that NE> TH2 is not satisfied (S44: NO), the process proceeds to step S44a (negative pressure determination means, intake determination means), and the intake pressure acquired in step S40 is higher than a predetermined value set in advance. It is determined whether or not it is a negative pressure state, in other words, whether or not the intake pressure (negative pressure) is sufficiently close to the atmospheric pressure. The predetermined value may be set to atmospheric pressure. Alternatively, in step S44a, it may be determined whether or not the intake air amount acquired in step S40 is a low intake state in which the intake air amount is smaller than a predetermined value set in advance.

  If it is determined that the state is a high negative pressure state (or a small intake state) (S44a: YES), it is determined as the “starting period” in the subsequent step S46. If it is determined that the state is not the high negative pressure state (or the low intake state) (S44a: NO), the process returns to step S44 without determining the start period. In short, even if NE falls due to automatic stop and NE ≦ TH2, when NE = TH2, it is not determined as the starting period, and thereafter when intake pressure rises and reaches a predetermined value ( Alternatively, when the intake air amount drops and reaches a predetermined value), the determination “after start” is switched to the determination “start period”, and the determination “after start” is continued until that time.

  On the other hand, if a negative determination is made in step S41 or step S42, the determination threshold value is set to a value higher than the determination threshold value TH2 calculated in step S43, assuming that the normal time shown in FIG. Using TH1a and TH1b, it is determined whether it is the starting period or after the starting. That is, in step S47 (starting period determining means), if it is determined that NE> TH1a, TH1b (S47: YES), “after starting” is determined (S45), and it is determined that NE> TH1a, TH1b is not satisfied. (S47: NO), it is determined as the “starting period” (S46).

  Also in the present embodiment described in detail above, the determination threshold value used for determining whether or not it is during the start period in which the start time injection control is performed is set to be lower than the normal time during the rotation descent period due to the automatic stop. (TH2 <TH1b), the same effects as the above (1) and (2) according to the first embodiment can be obtained.

  By the way, in the case where NE is lowered with the automatic stop and is lowered to the determination threshold TH2 and the injection control is performed with the injection amount at the time of starting, even if NE is reduced to TH2, when NE becomes TH2, it is strictly The crankshaft 31 is still slightly rotated. Therefore, the actual intake air amount becomes smaller than the intake air amount expected for the starting injection amount. Further, due to the remaining wet fuel vaporization, there may be an excess of the shortage of wet fuel expected in the starting injection amount. That is, if the injection amount at the start is injected immediately after NE = TH2, there is a concern that the excessive fuel state cannot be avoided reliably.

  In view of this point, in the present embodiment, even when NE decreases due to automatic stop and becomes equal to or less than the determination threshold value TH2, it remains in the post-start state until the high negative pressure state (or the low intake state) is reached. Since the determination that it is present is continued, it is possible to reliably avoid an excessive fuel state caused by injecting the starting injection amount.

(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.

  The determination threshold TH2 is preferably set to a value lower than the rotation speed when the engine 30 is idling.

  The determination threshold value TH2 used during the rotation descent period may be set to zero.

  In each of the above embodiments, the engine rotational speed NE is calculated based on the detection value of the crank angle sensor 21, and the calculated NE is compared with the determination thresholds TH1a, TH1b, TH2, and any of the start period and after the start is started. Is determined. On the other hand, the intake pressure calculated based on the detection value of the intake pressure sensor 23 or the intake air amount calculated based on the detection value of the air flow meter 24 may be substituted for the NE used for the determination.

  For example, if 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 if intake pressure <intake pressure threshold value, NE> determination threshold is assumed and the engine is started If the intake pressure is greater than or equal to the threshold for intake pressure, it may be determined that NE ≦ the determination threshold and the start period is determined. Alternatively, if the intake air amount> the threshold value for the intake air amount, it is determined that NE> the determination threshold value, and it is determined that the engine has been started. If the intake air amount ≦ the threshold value for the intake pressure, the NE is determined to be the determination threshold value. You may make it determine with a starting period. However, it is desirable to set the intake pressure threshold value higher during the rotation descent period due to the automatic stop than during normal rotation, and the intake air amount threshold value during the rotation descent period due to the automatic stop is higher than during normal rotation. It is desirable to set it low.

  DESCRIPTION OF SYMBOLS 10 ... ECU (startup injection control means, post-startup injection control means), S14, S17, S24, S27, S37 ... Start period determination means, S34 ... Enst determination means, S44a ... Negative pressure determination means, intake determination means, TH1a , TH1b, TH2...

Claims (7)

Start period determination means for determining that the operating state of the internal combustion engine is in the start period when the engine rotation speed of the internal combustion engine is equal to or less than a predetermined determination threshold;
When it is determined that the engine is in the start period, the start-time injection control means for controlling the fuel injection valve to inject an amount of fuel set as the start-time injection amount;
A post-startup injection control means for controlling the fuel injection valve to inject an amount of fuel calculated based on the engine rotational speed and the engine load each time in a post-startup state that is determined not to be the start-up period;
With
The internal combustion engine has an idle stop function for automatic stop and automatic restart,
The determination threshold value is set lower during a rotation descent period in which the fuel injection is cut and the engine rotation speed is reduced due to the occurrence of the automatic stop request, compared to a normal time other than the rotation descent period. A fuel injection control device.   The fuel injection control device according to claim 1, wherein the determination threshold is set to a higher value as the temperature of the internal combustion engine is lower.   3. The fuel injection control device according to claim 1, wherein the determination threshold is set to a higher value as the elapsed time from the initial start time of the internal combustion engine is shorter. When the automatic stop request is generated, fuel injection is cut and the determination threshold value used when the engine speed decreases is set to zero, and the internal combustion engine is stopped when the zero state continues for a predetermined time. Equipped with an engine stall determination means for determining the engine stall,
The starting period determining means includes
If the engine speed falls below the determination threshold during the rotation descent period, the determination that the engine is in the post-start state is continued until the engine stall determination is made thereafter, and the engine stall determination is performed. The fuel injection control device according to any one of claims 1 to 3, wherein the fuel injection control device switches to the determination that the start period is reached. A negative pressure determination means for determining whether or not the negative pressure generated in the intake pipe is in a high negative pressure state where the negative pressure is a predetermined value or more;
The starting period determining means includes
If the engine rotational speed becomes equal to or lower than the determination threshold during the rotation descent period, the determination that the post-start state is continued until the high negative pressure state is subsequently determined. The fuel injection control device according to any one of claims 1 to 3, wherein the fuel injection control device switches to the determination that the start period is reached when the state is determined. Intake determination means for determining whether or not the intake flow rate is a small intake state in which the intake flow rate is a predetermined value or less,
The starting period determining means includes
If the engine rotational speed becomes equal to or lower than the determination threshold value during the rotation descent period, then the determination that the engine is in the post-start state is continued until the low intake state is determined. The fuel injection control device according to any one of claims 1 to 3, wherein the fuel injection control device is switched to the determination that the start period is reached at the determined time.   The fuel injection control device according to any one of claims 1 to 6, wherein the determination threshold value is set to zero during the rotation descent period.

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