JP2008232007A - Start control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a start control device of an internal combustion engine capable of quickly completing the start while preventing the degradation of emission and the deterioration of fuel economy during the starting. <P>SOLUTION: When the difference between an intake pipe pressure and a fuel injection permissible pressure final value exceeds a starter high rotation determination constant α, the reduction rate of the intake pipe pressure is determined to be slower than normal. In this case, the amount of power supply to a starter motor is so corrected that the starter motor can be rotated at a high speed (step 134). When the difference between the intake pipe pressure and the fuel injection permissible pressure final value is less than a starter low rotation determination constant β, the reduction rate of the intake pipe pressure is determined to be faster than normal. In this case, the amount of power supply to the starter motor is so corrected that the starter motor can be rotated at a low speed (step 138). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a start control device for an internal combustion engine.

In general, when the internal combustion engine is started, the following conditions exist, so that the combustion state tends to deteriorate.
(1) Since the negative pressure in the place where fuel is injected (in the intake port in the case of port injection, in the cylinder in the case of in-cylinder injection) is not sufficient and the pressure is close to atmospheric pressure, Difficult to vaporize.
(2) Since the engine speed is low, there is little turbulence in the airflow.
(3) The wall on which the injected fuel collides is wet with fuel adhering during engine operation. While the engine is stopped, the fuel adhering to the wall surface evaporates and the wall surface dries out. For this reason, at the time of start-up, fuel for wetting the wall surface is also required, so that the fuel contributing to combustion is likely to be insufficient.
(4) At the time of cold start, the temperature of the engine main body including the wall to which the fuel adheres is low overall, and the fuel is more difficult to atomize.

  For this reason, at the time of start-up, unburned fuel that has not contributed to combustion is easily discharged as HC or CO, and emissions are likely to deteriorate. Further, since the fuel that has not contributed to the combustion is wasted, the amount of fuel required for starting tends to increase, and the fuel consumption tends to deteriorate. In particular, a vehicle such as a hybrid vehicle or a vehicle having an idling stop function is likely to be a problem in a vehicle that repeats automatic stop / automatic start of the internal combustion engine during traveling.

  In order to solve the problem at the time of starting as described above, Japanese Patent Laid-Open No. 2006-144725 discloses that the fuel pressure in the pressure accumulating chamber and the negative pressure of the intake pipe become equal to or greater than a predetermined value when the cylinder internal combustion engine is cold-started. Until now, a fuel injection control device is disclosed in which engine start is not permitted. According to this device, the engine start is not permitted until the fuel pressure in the pressure accumulating chamber and the intake pipe negative pressure are equal to or higher than predetermined values, that is, until the fuel is easily atomized. For this reason, the amount of fuel discharged without being combusted at the time of starting can be suppressed.

JP 2006-144725 A JP 2005-315196 A JP 2004-52613 A JP-A-6-323168

  The intake pipe negative pressure at the time of starting is generated when the internal combustion engine is cranked by the starter motor. In this case, the intake pipe negative pressure increasing speed (absolute pressure decreasing speed) also varies depending on environmental conditions and engine conditions. In the above-described conventional device, the engine start is not permitted unless the intake pipe negative pressure exceeds a predetermined value. Therefore, if the intake pipe negative pressure rises slowly, it takes time to start and the start completion is delayed. . If starting takes a long time, drivability may be adversely affected particularly in the case of a vehicle that automatically stops and starts, which is not preferable.

  The present invention has been made in view of the above points, and provides an internal combustion engine start control device capable of quickly completing engine start while preventing deterioration of emissions and fuel consumption at the time of engine start. With the goal.

In order to achieve the above object, a first invention is a start control device for an internal combustion engine,
A starter that cranks the internal combustion engine at start-up;
Injection field pressure acquisition means for detecting or estimating the pressure of the field at which the fuel is injected as an injection field pressure at start-up;
A rotational speed control means for controlling the rotational speed of the starter based on the injection field pressure at the start;
It is characterized by providing.

The second invention is the first invention, wherein
The rotation speed control means includes high rotation means for performing correction to increase the rotation speed of the starter when the rate of decrease in the injection field pressure is slower than a predetermined reference.

The third invention is the first or second invention, wherein
The rotation speed control means includes a low rotation speed reduction means for performing correction to lower the rotation speed of the starter when the rate of decrease in the injection field pressure is faster than a predetermined reference.

According to a fourth invention, in any one of the first to third inventions,
The fuel injection start timing control means for starting the fuel injection after waiting for the injection field pressure to drop to a predetermined determination pressure at the start after cranking is started.

The fifth invention is the fourth invention, wherein
It is characterized by comprising determination pressure setting means for setting the determination pressure based on the saturated vapor pressure characteristic of the fuel.

The sixth invention is the fourth or fifth invention, wherein
It is characterized by comprising determination pressure correction means for correcting the determination pressure based on parameters relating to the environment surrounding the internal combustion engine.

According to a seventh invention, in any one of the first to sixth inventions,
Leakage or clogging of the intake system of the internal combustion engine or abnormality of the starter is detected based on the correction amount applied to the starter by the rotation speed control means and / or the temporal transition of the injection field pressure. An abnormality detection means is provided.

  According to the first invention, at the time of start-up, the rotation speed of the starter can be controlled based on the pressure of the field where fuel is injected (injection field pressure). At the time of start-up, the internal combustion engine is cranked by the starter, thereby generating a negative pressure in the fuel injection field. For this reason, the negative pressure of the fuel injection field depends on the rotation speed of the starter. If the negative pressure of the fuel injection field is not sufficiently large at the time of start-up, fuel atomization (vaporization) is poor, the fuel is difficult to burn, and the time required to complete the start-up tends to be long. On the contrary, if the starter rotation speed is increased as the injection field pressure becomes lower than necessary, the power consumption increases or the starter is worn out. According to the first aspect of the invention, by controlling the starter rotation speed based on the injection field pressure, the injection field pressure is quickly and surely reduced at the time of start-up, fuel atomization is promoted, and the fuel is easily combusted. can do. For this reason, it is possible to reduce the amount of fuel discharged as HC, CO or the like in the exhaust gas without being burned, and to improve the emission and fuel consumption at the start. In addition, the time required to complete the start can be shortened. Furthermore, since it is possible to prevent the starter rotation speed from becoming higher than necessary, it is possible to suppress power consumption and extend the life of the starter.

  According to the second aspect of the invention, when the injection field pressure decrease rate (negative pressure increase rate) is slower than the reference, the injection field pressure decrease rate can be recovered by increasing the rotation speed of the starter. . Thereby, it can prevent more reliably that start completion is overdue.

  According to the third invention, when the injection field pressure decrease rate (negative pressure increase rate) is higher than necessary, the starter rotation number is decreased more than necessary by lowering the starter rotation number. It can be surely prevented. For this reason, power consumption can be suppressed reliably and the life of the starter can be further extended.

  According to the fourth invention, at the time of starting, fuel injection can be started after the injection field pressure becomes sufficiently low (after the negative pressure becomes sufficiently high). For this reason, immediately after the start of injection, the vaporization (boiling under reduced pressure) of the fuel can be promoted, and the injected fuel can be reliably burned. As a result, it is possible to reduce the amount of fuel that is unburned and discharged as exhaust gas, and to further improve emissions and fuel consumption.

  According to the fifth aspect, the determination pressure for determining permission to start fuel injection can be set based on the saturated vapor pressure characteristic of the fuel. For this reason, after cranking starts, the period during which fuel injection is prohibited can be set to an optimum length according to the saturated vapor pressure characteristic of the fuel. Therefore, it is possible to perform a quick start while sufficiently improving emission and fuel consumption.

  According to the sixth aspect, the determination pressure can be corrected based on a parameter (environment parameter) related to the environment surrounding the internal combustion engine. The ease of fuel evaporation varies with environmental parameters. According to the sixth aspect, after the cranking starts, the period during which fuel injection is prohibited can be set to a more appropriate length in consideration of the influence of environmental parameters.

  According to the seventh aspect of the present invention, by using the correction amount added to the starter rotation speed at the time of start-up or the time transition of the injection field pressure, leakage or clogging of the intake system of the internal combustion engine, or starter abnormality is prevented. It can be detected with high accuracy.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited.

  An intake passage 12 and an exhaust passage 14 communicate with each other in the cylinder of the internal combustion engine 10. An air flow meter 16 that detects an intake air amount Ga is disposed in the intake passage 12. A throttle valve 18 is disposed downstream of the air flow meter 16. The opening degree of the throttle valve 18 is adjusted by the operation of the throttle motor 20. A throttle position sensor 22 for detecting the opening degree of the throttle valve 18 is disposed in the vicinity of the throttle valve 18. An accelerator position sensor 24 that detects the amount of depression of the accelerator pedal is provided in the vicinity of the accelerator pedal.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injector 26 for injecting fuel into the intake port 11. The internal combustion engine 10 is not limited to the port injection type as shown in the figure, but may be a direct injection type that directly injects fuel into the cylinder, and also performs port injection and in-cylinder injection. It may be used in combination. Each cylinder of the internal combustion engine 10 is further provided with an intake valve 28, a spark plug 30, and an exhaust valve 32.

  A crank angle sensor 38 is attached in the vicinity of the crankshaft 36 of the internal combustion engine 10. According to the output of the crank angle sensor 38, the crank angle and the engine speed NE can be detected.

  Further, the system of the present embodiment includes an intake pressure sensor 40 that detects the pressure in the intake port 11, a water temperature sensor 42 that detects the cooling water temperature of the internal combustion engine 10, and a starter motor 44 that cranks the internal combustion engine 10 during startup. And a fuel property sensor 46 for detecting the property of the fuel supplied to the internal combustion engine 10 and a fuel temperature sensor 48 for detecting the temperature of the fuel supplied to the internal combustion engine 10.

  Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is electrically connected to the various sensors and actuators described above.

  In the present embodiment, it is assumed that the internal combustion engine 10 is mounted on an idling stop vehicle or a hybrid vehicle. In these vehicles, the automatic stop and automatic start of the internal combustion engine 10 are repeatedly executed during traveling. In the case of a hybrid vehicle, the starter motor 44 may not be dedicated to starting, and may function as a generator except during starting. The present invention can also be applied to a system in which the internal combustion engine 10 is not automatically stopped and automatically started.

[Features of Embodiment 1]
As described above, when the internal combustion engine 10 is started, generally, unburned fuel that has not contributed to combustion tends to be discharged as HC or CO, and fuel consumption tends to increase. FIG. 2 is a diagram showing the relationship between the absolute pressure in the intake port 11 at the time of starting (hereinafter also referred to as “intake pipe pressure”), the required injection amount at the starting time, and the unburned exhaust gas amount at the starting time. The startup required injection amount is the amount of fuel necessary for startup, and the startup unburned exhaust gas amount is the amount of HC and CO discharged at startup.

  The fuel injected from the fuel injector 26 is more atomized (vaporized) as the intake pipe pressure is lower, that is, as the negative pressure in the intake port 11 is higher. Conversely, the higher the intake pipe pressure is and the closer it is to atmospheric pressure, the more difficult the fuel atomizes. Thus, the higher the intake pipe pressure, the higher the proportion of injected fuel that does not contribute to combustion. In addition, it is necessary to inject more fuel by that amount. Therefore, as shown in FIG. 2, as the intake pipe pressure increases, both the unburned exhaust gas amount at start and the required injection amount at start increase.

  FIG. 3 is a timing chart for explaining the start control of the present embodiment. As shown in FIG. 3, when cranking of the internal combustion engine 10 is started by the starter motor 44 at the time of starting, negative pressure is generated in the intake port 11 as the engine speed (cranking speed) increases. Occurs, and the intake pipe pressure decreases. In addition, the injection permission flag in FIG. 3 is a flag that indicates whether fuel injection from the fuel injector 26 is permitted or prohibited.

  In this embodiment, in order to reduce the unburned exhaust gas amount at start and the required injection amount at start, as shown in FIG. 3, the intake air detected by the intake pressure sensor 40 after the cranking of the internal combustion engine 10 is started. The fuel injector 26 is allowed to inject fuel after waiting for the pipe pressure to drop to a predetermined negative determination pressure. As a result, the supply of fuel into the intake port 11 can be started after the negative pressure in the intake port 11 becomes sufficiently large and fuel atomization (vaporization) is sufficiently promoted. For this reason, since the injected fuel can be reliably atomized and burned, the amount of unburned exhaust gas at the start and the required injection amount at the start can be reduced, and the emission and fuel consumption at the start can be improved.

  Further, in this embodiment, at the time of starting, the rotation speed of the starter motor 44 is controlled according to the intake pipe pressure. Specifically, when it is determined that the rate of decrease in the intake pipe pressure is slower than normal, correction is made so that the rotation speed of the starter motor 44 is increased. This ensures that the time it takes for the intake pipe pressure to drop to the negative determination pressure is prevented from becoming excessively long even when the rate of decrease in the intake pipe pressure is slower than normal for some reason. can do. Therefore, the start completion of the internal combustion engine 10 can be prevented from being delayed, and adverse effects such as drivability deterioration can be prevented.

  On the other hand, when it is determined that the rate of decrease in the intake pipe pressure at the time of starting is faster than usual, in the present embodiment, correction is made so that the rotation speed of the starter motor 44 is lowered. Thereby, when the rate of decrease in the intake pipe pressure is higher than necessary at the time of starting, the rotation speed of the starter motor 44 is lowered, so that the power consumption of the starter motor 44 can be reduced by that amount. For this reason, the fuel consumption performance as a whole can be improved and the life of the starter motor 44 can be extended.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time. According to the routine shown in FIG. 4, it is first determined whether or not start is requested (step 100). If it is determined that the start is not requested, the current processing cycle is terminated as it is.

  On the other hand, if it is determined in step 100 that the start is requested, the starter motor 44 is energized (step 102). Thereby, the internal combustion engine 10 is cranked by the starter motor 44. Next, the intake pipe pressure detected by the intake pressure sensor 40 is read (step 104). Subsequently, the basic value of the fuel injection permission pressure is calculated (step 106). The fuel injection permission pressure corresponds to the determination negative pressure in FIG. FIG. 5 is a subroutine showing the processing of step 106.

  According to the processing of the subroutine shown in FIG. 5, first, the saturated vapor pressure line of the fuel is detected (step 108). FIG. 6 is a map showing the saturated vapor pressure line of the fuel, and this map is stored in the ECU 50. The degree of fuel atomization can be determined by the value of the saturated vapor pressure. As shown in FIG. 6, the higher the fuel temperature, the higher the saturated vapor pressure of the fuel. In addition, the saturated vapor pressure of the fuel varies depending on the type of fuel (for example, a heavy fuel or a light fuel, or a difference in alcohol content). The map shown in FIG. 6 shows saturated vapor pressure lines of three types of fuels A, B, and C. In step 108, it is determined based on the detection result of the fuel property sensor 46 whether the fuel supplied to the internal combustion engine 10 is A, B, or C.

  Next, the temperature of the fuel supplied to the internal combustion engine 10 is detected by the fuel temperature sensor 48 (step 110). Subsequently, the saturated vapor pressure of the fuel is calculated by applying the fuel temperature detected in step 110 to the saturated vapor pressure line detected in step 108 (step 112). The smaller the saturated vapor pressure, the less likely the fuel will atomize. For this reason, when the saturated vapor pressure of the fuel is small, it is desirable to start fuel injection after the intake pipe pressure has decreased to a lower value. Therefore, in step 106 of FIG. 4, the basic value of the fuel injection permission pressure is calculated to be smaller as the saturated vapor pressure of the fuel calculated as described above is smaller.

  In step 108, when the detection result by the fuel property sensor 46 is an intermediate property of the fuels A, B, and C, the saturated vapor pressure line in the map of FIG. A saturated vapor pressure line corresponding to the detection result may be obtained.

  Subsequent to the processing of step 106 in FIG. 4, the correction value of the fuel injection permission pressure is calculated (step 114). FIG. 7 is a subroutine showing the processing of step 114. According to the processing of the subroutine shown in FIG. 7, first, an environmental parameter that is a parameter related to the environmental temperature of the internal combustion engine 10 is acquired (step 116). As this environmental parameter, for example, the cooling water temperature detected by the water temperature sensor 42, the intake air temperature, the outside air temperature, or the like can be used.

  Subsequently, a correction value for the fuel injection permission pressure is calculated (step 118). The higher the environmental parameter is, the more easily the fuel injected from the fuel injector 26 is atomized. The lower the environmental parameter is, the more difficult the fuel is atomized. The correction value of the fuel injection permission pressure is a correction value for correcting this influence. FIG. 8 is a map for obtaining the correction value of the fuel injection permission pressure based on the environmental parameters. In step 118, as shown in the figure, the lower the environmental parameter is, the smaller the correction value for the fuel injection permission pressure is calculated.

  Subsequently, a process of guarding the calculated correction value of the fuel injection permission pressure is executed. That is, the calculated correction value is compared with a predetermined lower limit value (step 120), and when the correction value is less than the lower limit value, the correction value is replaced with the lower limit value (step 122). The calculated correction value is compared with a predetermined upper limit value (step 124). If the correction value exceeds the upper limit value, the correction value is replaced with the upper limit value (step 124). In other cases, the value calculated in step 118 is directly used as a correction value for the fuel injection permission pressure.

  After the correction value of the fuel injection permission pressure is calculated as described above, the fuel injection permission pressure is then obtained by adding the correction value and the basic value of the fuel injection permission pressure calculated in step 106 above. Is calculated (step 128 in FIG. 4).

  Subsequently, the rotational speed control of the starter motor 44 is executed (step 130). FIG. 9 is a subroutine showing the processing of step 130. According to the processing of this subroutine, first, the difference between the current intake pipe pressure detected in step 104 and the final fuel injection permission pressure value calculated in step 128 determines the starter high rotation determination constant α. It is determined whether or not it exceeds (step 132).

  If the determination in step 132 is affirmative, it can be determined that the rate of decrease in the intake pipe pressure is slower than normal. Therefore, in this case, the energization amount to the starter motor 44 is corrected so that the starter motor 44 rotates at a higher speed (step 134).

  On the other hand, if the determination in step 132 is negative, then the difference between the current intake pipe pressure detected in step 104 and the final fuel injection permission pressure value calculated in step 128 is calculated. Then, it is determined whether or not the starter speed reduction determination constant β is less than (step 136). If this determination is affirmative, it can be determined that the rate of decrease in the intake pipe pressure is faster than normal. In this case, there is no problem even if the number of revolutions of the starter motor 44 is slightly reduced. Therefore, in this case, the energization amount to the starter motor 44 is corrected so that the starter motor 44 rotates at a low speed (step 138).

  Subsequent to step 130 in FIG. 4, a process for detecting an abnormality in the intake system or the starter is executed (step 140). The process of step 140 will be described later.

  Following the processing in step 140, it is determined whether or not the current intake pipe pressure detected in step 104 has decreased to the fuel injection permission pressure final value calculated in step 128 (step 142). As a result, if it is determined that the intake pipe pressure is still larger than the final value of the fuel injection permission pressure, fuel injection from the fuel injector 26 is prohibited (step 144). On the other hand, if it is determined in step 142 that the intake pipe pressure has decreased to the fuel injection permission pressure, fuel injection from the fuel injector 26 is permitted (step 146), and fuel injection is executed.

  As described above, according to the present embodiment, when the internal combustion engine 10 is started, the intake pipe pressure, which is the pressure at the place where fuel is injected (inside the intake port 11), is reduced to the fuel injection permission pressure. Wait and start fuel injection. For this reason, atomization (vaporization) of fuel can be sufficiently promoted immediately after the start of fuel injection. Therefore, it is possible to reduce the amount of fuel discharged without contributing to combustion at the time of starting, and as a result, it is possible to improve the starting emission and fuel consumption.

  Further, according to the present embodiment, when it is determined that the rate of decrease in the intake pipe pressure is slower than normal at the time of starting, the intake pipe pressure is reduced by correcting the starter motor 44 so that the number of rotations is increased. You can recover by increasing the speed. For this reason, even if the rate of decrease in the intake pipe pressure is slower than usual for some reason, it is possible to reliably prevent the time required for the intake pipe pressure to decrease to the fuel injection permission pressure from becoming excessively long. Can do. Therefore, it is possible to prevent the start completion from being delayed, and it is possible to prevent the occurrence of adverse effects such as drivability deterioration.

  Conversely, when it is determined that the rate of decrease in the intake pipe pressure at the time of starting is faster than normal, it is possible to correct the rotation speed of the starter motor 44 to be low. Thereby, since the rotation speed of the starter motor 44 can be suppressed to a necessary and sufficient rotation speed, power consumption can be reduced. Therefore, the fuel efficiency performance as a whole can be improved, and the life of the starter motor 44 can be extended.

  Moreover, according to this embodiment, the saturated vapor pressure of the fuel can be calculated, and the fuel injection permission pressure can be set according to the value. For this reason, after starting, the period during which fuel injection is prohibited can be set to a length that is not excessive or insufficient in accordance with the fuel evaporation characteristics. For this reason, starting can be performed quickly, and fuel consumption and emission can be reliably improved.

  Furthermore, according to the present embodiment, the fuel injection permission pressure can be corrected according to the environmental parameters of the internal combustion engine 10. That is, the fuel injection permission pressure can be set in consideration of the influence of environmental conditions on the fuel evaporation characteristics. For this reason, after starting, the period during which fuel injection is prohibited can be set to a more appropriate length.

  Next, the process of detecting an abnormality in the intake system or starter in step 140 will be described. FIG. 10 is a subroutine showing the processing of step 140. According to this subroutine processing, first, the starter rotational speed correction amount corrected in the rotational speed control of the starter motor 44 in step 130 is read (step 148). Next, a starter rotation speed abnormality determination value for determining abnormality of the starter motor 44 is acquired (step 150).

  Subsequently, a determination value for determining an abnormality in the intake pipe pressure is acquired (step 152). FIG. 11 is a map showing the abnormality determination value of the intake pipe pressure acquired in step 152. The solid line in FIG. 11 is a graph showing a typical transition of the intake pipe pressure over time after the start of cranking, and the broken lines above and below the solid line are graphs showing the normal range of the intake pipe pressure. When the intake pipe pressure is lower than this normal range, that is, when the negative pressure in the intake pipe does not increase normally, there is a leak in the intake system such as the intake passage 12 or the starter motor 44 is abnormal. It can be determined that the cranking speed is lower than the indicated value. On the contrary, when the intake pipe pressure is higher than the normal range, that is, when the negative pressure in the intake pipe is abnormally increased, the intake system (air cleaner) is clogged or the starter motor 44 is abnormal. Thus, it can be determined that the cranking rotation speed is higher than the indicated value. In step 152, an abnormal upper limit determination value and an abnormal lower limit determination value corresponding to the elapsed time after the start of cranking are acquired based on the map shown in FIG.

  Subsequently, it is determined whether or not the current intake pipe pressure acquired in step 104 is in a normal range defined by the abnormal upper limit determination value and abnormal lower limit determination value acquired in step 152 ( Step 154). As a result, when it is determined that the intake pipe pressure is outside the normal range, it is determined that there is an abnormality in the intake system (leakage or clogging) or an abnormality in the starter motor 44 (step 156).

  On the other hand, if it is determined in step 154 that the intake pipe pressure is within the normal range, then the absolute value of the starter rotational speed correction amount acquired in step 148 is acquired in step 150. It is determined whether or not the starter rotational speed abnormality determination value is below (step 158). As a result, if it is determined that the absolute value of the starter rotational speed correction amount is equal to or greater than the starter rotational speed abnormality determination value, the intake pipe pressure has become an abnormal value due to leakage or clogging of the intake system, or It can be determined that an abnormality has occurred in the motor 44 and the actual starter rotation speed has not responded normally to the correction. Therefore, in this case as well, it is determined that there is an abnormality in the intake system or the starter motor 44 (step 156).

  On the other hand, if it is determined in step 158 that the absolute value of the starter rotation speed correction amount is less than the starter rotation speed abnormality determination value, there is no abnormality in either the intake system or the starter motor 44. It is determined that it is normal (step 160).

  In the present embodiment, by executing the processing of the routine shown in FIG. 10 described above, if an abnormality occurs in the intake system or the starter motor 44, the abnormality can be detected with high accuracy.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. As described above, the present invention can also be applied to an in-cylinder direct injection internal combustion engine that directly injects fuel into the cylinder. In that case, instead of the intake pipe pressure, the same control as in the above embodiment may be performed using the in-cylinder pressure. The in-cylinder pressure may be detected by providing an in-cylinder pressure sensor 52. Alternatively, a value detected by the intake pressure sensor 40 during the valve opening period of the intake valve 28 may be used as the in-cylinder pressure. This is because when the intake valve 28 is open, the intake pipe pressure becomes equal to the in-cylinder pressure. In the present invention, the intake pipe pressure or the in-cylinder pressure, that is, the pressure in the field where fuel is injected may be estimated from the engine speed or the like.

  In the first embodiment described above, the intake pressure sensor 40 corresponds to the “injection field pressure acquisition means” in the first invention. Further, when the ECU 50 executes the process of step 130 (the routine shown in FIG. 9), the “rotation speed control means” in the first aspect of the invention executes the processes of steps 132 and 134 described above. When the “high rotation means” in the second aspect of the invention executes the processing of steps 136 and 138, the “low rotation means” in the third aspect of the invention executes the processing of steps 140 to 146. The “fuel injection start timing control means” according to the fourth aspect of the invention executes the processing of step 106 (the routine shown in FIG. 5), whereby the “judgment pressure setting means” according to the fifth aspect of the invention is the step 114. By executing the processing of (the routine shown in FIG. 7), the “determination pressure correction means” in the sixth aspect of the present invention is Step 140 is "abnormality detection means" in the invention of the seventh by executing the processing of (routine shown in FIG. 10) are realized respectively.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the relationship between the intake pipe pressure at the time of starting, the required injection quantity at the time of starting, and the amount of unburned exhaust gas at the time of starting. It is a timing chart for demonstrating the starting control of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a map which shows the saturated vapor pressure line of a fuel. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a map for calculating | requiring the correction value of fuel-injection permission pressure based on an environmental parameter. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a map which shows the abnormality determination value of an intake pipe pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Intake port 12 Intake passage 14 Exhaust passage 16 Air flow meter 18 Throttle valve 26 Fuel injector 30 Spark plug 40 Intake pressure sensor 42 Water temperature sensor 50 ECU

Claims (7)

A starter that cranks the internal combustion engine at start-up;
Injection field pressure acquisition means for detecting or estimating the pressure of the field at which fuel is injected as an injection field pressure at the time of start-up;
Rotational speed control means for controlling the rotational speed of the starter based on the injection field pressure at the start,
A start control device for an internal combustion engine, comprising:   The rotation speed control means includes high rotation speed means for performing correction for increasing the rotation speed of the starter when the rate of decrease in the injection field pressure is slower than a predetermined reference. Start control device for internal combustion engine.   The rotation speed control means includes low rotation speed reduction means for performing correction to lower the rotation speed of the starter when the rate of decrease in the injection field pressure is faster than a predetermined reference. 3. A start control device for an internal combustion engine according to 2.   4. A fuel injection start timing control means for starting fuel injection after starting the cranking and waiting for the injection field pressure to drop to a predetermined judgment pressure at the start. The start control device for an internal combustion engine according to claim 1.   5. The start control device for an internal combustion engine according to claim 4, further comprising determination pressure setting means for setting the determination pressure based on a saturated vapor pressure characteristic of fuel.   6. The start control device for an internal combustion engine according to claim 4, further comprising determination pressure correction means for correcting the determination pressure based on a parameter relating to an environment surrounding the internal combustion engine.   Leakage or clogging of the intake system of the internal combustion engine or abnormality of the starter is detected based on the correction amount applied to the starter by the rotation speed control means and / or the temporal transition of the injection field pressure. The start control device for an internal combustion engine according to any one of claims 1 to 6, further comprising abnormality detection means.

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