JP4049943B2 - Fuel injection control device for in-cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a main fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine, and an auxiliary fuel injection valve that injects fuel into an intake passage of the internal combustion engine. The present invention relates to a fuel injection control device for a direct injection internal combustion engine that temporarily injects fuel from an auxiliary fuel injection valve as required.
[0002]
[Prior art]
2. Description of the Related Art A cylinder injection type internal combustion engine that realizes stratified combustion at a partial load to improve fuel efficiency by directly injecting fuel into a combustion chamber in a compression stroke is known (Japanese Patent Laid-Open No. 10-176574, JP (Kaihei 10-18884).
[0003]
In such a cylinder injection internal combustion engine, in order to sufficiently atomize the fuel, it is necessary to pressurize the fuel with a high-pressure fuel pump and inject the fuel into the combustion chamber at a high pressure. However, at the time of cold start, fuel may not be atomized sufficiently due to low temperature, and the required amount of fuel is supplied into the combustion chamber because the friction of the internal combustion engine becomes high and the cranking speed does not increase sufficiently. In some cases, the startability tends to deteriorate.
[0004]
For this reason, in the prior art, in addition to the main fuel injection valve that directly injects fuel into the combustion chamber, an auxiliary fuel injection valve is provided in the intake passage capable of low pressure injection. With this auxiliary fuel injection valve, at the time of low temperature start, fuel is injected into the intake passage until the start of the internal combustion engine is completed. As a result, sufficient fuel is supplied to the combustion chamber even at a low temperature start to improve startability.
[0005]
[Problems to be solved by the invention]
However, even when the start of the internal combustion engine itself is successfully completed by performing fuel injection by the auxiliary fuel injection valve at low temperature start, depending on the engine temperature, particularly when the degree of low temperature is large, There is a case where the increase in the rotational speed of the internal combustion engine becomes unstable. This is because, even after the number of revolutions of the internal combustion engine has increased to the number of revolutions that is determined to have been completed, there are problems such as insufficient atomization of fuel by the main fuel injection valve depending on the low temperature level. It means that
[0006]
If the increase in the rotational speed becomes unstable in this manner, the rotational speed of the internal combustion engine may decrease after the start is completed, causing an engine stall. In addition, since the rotational speed does not increase smoothly, there is a risk of adversely affecting various controls using the rotational speed as a parameter.
[0007]
The present invention relates to an in-cylinder injection internal combustion engine having an auxiliary fuel injection valve that injects fuel into an intake passage together with a main fuel injection valve that directly injects fuel into a combustion chamber. The purpose is to prevent rotational instability.
[0008]
[Means for Solving the Problems]
A fuel injection control device for a direct injection internal combustion engine according to claim 1, wherein a main fuel injection valve for directly injecting fuel into a combustion chamber of the internal combustion engine and an auxiliary fuel injection valve for injecting fuel into an intake passage of the internal combustion engine And low temperature When starting The above Along with fuel injection by the main fuel injection valve, In order to compensate for the shortage due to the deterioration of atomization of the fuel injected from the main fuel injection valve Auxiliary fuel injection valve Fuel injection by Temporarily Execution A fuel injection control device for an in-cylinder internal combustion engine, wherein when the fuel is injected from the auxiliary fuel injection valve, the rotational speed of the internal combustion engine is More than the rotation speed judgment value to judge the start completion of the internal combustion engine The injection is continued until the specified rotational speed is exceeded, and the specified rotational speed is set higher on the low temperature side of the internal combustion engine than on the high temperature side.
[0009]
Thus, when the start of the internal combustion engine is completed, the fuel injection from the auxiliary fuel injection valve is not stopped immediately, but the injection is continued until the rotational speed of the internal combustion engine exceeds the specified rotational speed. The prescribed rotational speed is set higher on the low temperature side of the internal combustion engine than on the high temperature side. For this reason, even after the start is completed, sufficiently atomized fuel is supplied to the combustion chamber. In addition, the lower the temperature, the longer the fuel injection from the auxiliary fuel injection valve continues. Therefore, even if the temperature is extremely low, the rotation of the internal combustion engine is stabilized and a smooth increase in the number of revolutions can be realized. .
[0010]
Therefore, effects such as prevention of engine stall and prevention of adverse effects on various controls using the rotation speed as a parameter can be derived regardless of the degree of low temperature.
A fuel injection control device for a direct injection internal combustion engine according to claim 2, wherein a main fuel injection valve that directly injects fuel into a combustion chamber of the internal combustion engine, and an auxiliary fuel injection valve that injects fuel into an intake passage of the internal combustion engine. And low temperature When starting The above Along with fuel injection by the main fuel injection valve, In order to compensate for the shortage due to the deterioration of atomization of the fuel injected from the main fuel injection valve Auxiliary fuel injection valve Fuel injection by Temporarily Execution A fuel injection control device for an in-cylinder internal combustion engine that detects the temperature of the internal combustion engine and the temperature of the internal combustion engine detected by the engine temperature detection unit More than the rotation speed judgment value to judge the start completion of the internal combustion engine When setting the specified engine speed and setting the specified engine speed higher on the low temperature side of the internal combustion engine than on the higher side, and when injecting fuel from the auxiliary fuel injection valve And auxiliary fuel injection control means for continuing fuel injection from the auxiliary fuel injection valve until the rotational speed of the internal combustion engine exceeds the specified rotational speed set by the specified rotational speed setting means. To do.
[0011]
More specifically, as described above, the engine temperature detecting means, the specified rotational speed setting means, and the auxiliary fuel injection control means can be provided.
Here, when the auxiliary fuel injection control means injects the fuel from the auxiliary fuel injection valve, the auxiliary fuel injection control means starts from the auxiliary fuel injection valve until the rotational speed of the internal combustion engine exceeds the specified speed set by the specified speed setting means. The fuel injection continues. This prescribed rotational speed is set higher by the prescribed rotational speed setting means on the low temperature side of the internal combustion engine than on the high temperature side.
[0012]
For this reason, due to the same effect as in the first aspect, the rotation of the internal combustion engine is stabilized regardless of the low temperature level, and a smooth increase in the number of revolutions can be realized.
According to a third aspect of the present invention, there is provided a fuel injection control device for a cylinder injection type internal combustion engine, wherein the auxiliary fuel injection control means is configured so that the rotational speed of the internal combustion engine exceeds the specified rotational speed. The fuel injection by the auxiliary fuel injection valve is stopped when the fuel injection duration by the auxiliary fuel injection valve exceeds the time limit.
[0013]
In consideration of the fact that the start has not been completed for some reason, the fuel injection by the auxiliary fuel injection valve is stopped when the fuel injection duration by the auxiliary fuel injection valve exceeds the time limit. Thus, together with the operation and effect of claim 2, it is possible to prevent unnecessary fuel injection.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
FIG. 1 is a block diagram showing a schematic configuration of a direct injection internal combustion engine to which the above-described invention is applied and its control device.
[0015]
A gasoline engine (hereinafter abbreviated as “engine”) 2 as an in-cylinder internal combustion engine is mounted on an automobile in order to drive the automobile by its output. The engine 2 has four cylinders 2a. As shown in FIGS. 2 to 5, each cylinder 2 a includes a cylinder block 4, a piston 6 that reciprocates in the cylinder block 4, and a combustion chamber defined by a cylinder head 8 attached on the cylinder block 4. 10 are formed.
[0016]
Each combustion chamber 10 is provided with a first intake valve 12a, a second intake valve 12b, and a pair of exhaust valves 16. Among these, the first intake valve 12a is connected to the first intake port 14a, the second intake valve 12b is connected to the second intake port 14b, and the pair of exhaust valves 16 are connected to the pair of exhaust ports 18, respectively. .
[0017]
FIG. 2 is a plan sectional view of the cylinder head 8, and the first intake port 14a and the second intake port 14b are straight type intake ports extending substantially linearly as shown. A spark plug 20 is disposed at the center of the inner wall surface of the cylinder head 8. Further, a main injector 22 is arranged around the inner wall surface of the cylinder head 8 in the vicinity of the first intake valve 12a and the second intake valve 12b so that fuel can be directly injected into the combustion chamber 10.
[0018]
3 is a plan view of the top surface of the piston 6, FIG. 4 is a sectional view taken along line XX in FIG. 2, and FIG. 5 is a sectional view taken along line YY in FIG. As shown in the drawing, a concave portion 24 having a dome-shaped contour extending from the lower side of the main injector 22 to the lower side of the spark plug 20 is formed on the top surface of the piston 6 formed in a substantially chevron shape.
[0019]
As shown in FIG. 1, the first intake port 14 a of each cylinder 2 a is connected to a surge tank 32 via a first intake passage 30 a formed in the intake manifold 30. The second intake port 14b is connected to the surge tank 32 via the second intake passage 30b. Among these, the air flow control valve 34 is arranged in the second intake passage 30b. These air flow control valves 34 are connected via a common shaft 36 and are opened and closed by a negative pressure actuator 37 via this shaft 36. When the airflow control valve 34 is closed, a strong swirling flow is generated in the combustion chamber 10 by the intake air sucked only from the first intake port 14a.
[0020]
The surge tank 32 is connected to the air cleaner 42 via the intake duct 40. A throttle valve 46 driven by a motor 44 (DC motor or step motor) is disposed in the intake duct 40. The opening of the throttle valve 46 (throttle opening TA) is detected by a throttle opening sensor 46a, and the opening is controlled as described later. Further, each exhaust port 18 of each cylinder 2 a is connected to an exhaust manifold 48.
[0021]
A fuel distribution pipe 50 is provided in the cylinder head 8 in the vicinity of the first intake valve 12a and the second intake valve 12b. A main injector 22 provided in each cylinder 2a is connected to the fuel distribution pipe 50. When stratified combustion and homogeneous combustion are performed, fuel is directly injected into the combustion chamber 10 from the main injector 22.
[0022]
A sub-injector 52 is attached to the surge tank 32. As will be described later, fuel is temporarily injected from the sub-injector 52 into the surge tank 32 at a low temperature start. The sub-injector 52 can inject fuel in a highly atomized state having a very small particle diameter as compared with the main injector 22.
[0023]
A fuel distribution pipe 50 that distributes fuel to the main injector 22 is connected to a high pressure pump 54 via a high pressure fuel passage 54a. The high-pressure fuel passage 54 a is provided with a check valve 54 b that restricts fuel from flowing backward from the fuel distribution pipe 50 to the high-pressure pump 54 side. A low pressure pump 58 provided in the fuel tank 56 is connected to the high pressure pump 54 via a low pressure fuel passage 54c.
[0024]
The low pressure pump 58 sucks and discharges the fuel in the fuel tank 56, thereby pumping the fuel to the high pressure pump 54 through the low pressure fuel passage 54c. At the same time, the low-pressure fuel passage 54 c branches off in the middle and is connected to the sub-injector 52. Accordingly, the fuel in the fuel tank 56 is also pumped from the low pressure pump 58 to the sub-injector 52 through the low pressure fuel passage 54c.
[0025]
The high-pressure pump 54 is driven by a crankshaft (not shown) of the engine 2 to pressurize the fuel to a high pressure, and pressure-feeds the pressurized fuel into the fuel distribution pipe 50 through the high-pressure fuel passage 54a. The high-pressure pump 54 is provided with an electromagnetic spill valve 54d inside. When the electromagnetic spill valve 54d is open, the fuel supplied to the high-pressure pump 54 is returned to the fuel tank 56 side without being pressurized and pressurized to the fuel distribution pipe 50 side. On the other hand, when the electromagnetic spill valve 54d is closed, fuel is pressurized and fed from the high pressure pump 54 to the fuel distribution pipe 50 side through the high pressure fuel passage 54a. An electronic control unit (hereinafter referred to as “ECU”) 60 feedback-controls the opening / closing timing of the electromagnetic spill valve 54d with reference to the detection value of the fuel pressure sensor 50a attached to the fuel distribution pipe 50, and the fuel from the high-pressure pump 54 The fuel pressure in the fuel distribution pipe 50 is adjusted to an appropriate pressure by adjusting the amount of fuel that is pressurized and fed to the distribution pipe 50. An excess fuel return path in the fuel distribution pipe 50 and the low-pressure fuel path 54c is not shown.
[0026]
The ECU 60 comprises a digital computer, and is connected to each other via a bidirectional bus 62, a RAM (Random Access Memory) 64, a ROM (Read Only Memory) 66, a CPU (Microprocessor) 68, an input port 70 and an output port. 72.
[0027]
A throttle opening sensor 46 a that detects the throttle opening TA inputs an output voltage proportional to the opening of the throttle valve 46 to the input port 70 via the AD converter 73. A fuel pressure sensor 50 a provided in the fuel distribution pipe 50 inputs an output voltage proportional to the fuel pressure in the fuel distribution pipe 50 to the input port 70 via the AD converter 73. An accelerator opening sensor 76 is attached to the accelerator pedal 74, and an output voltage proportional to the amount of depression of the accelerator pedal 74 is input to the input port 70 via the AD converter 73. The top dead center sensor 80 generates an output pulse when, for example, the first cylinder of the cylinders 2 a reaches the intake top dead center, and this output pulse is input to the input port 70. The crank angle sensor 82 generates an output pulse every time the crankshaft rotates 30 degrees, and this output pulse is input to the input port 70. The CPU 68 calculates the current crank angle from the output pulse of the top dead center sensor 80 and the output pulse of the crank angle sensor 82, and calculates the engine speed from the frequency of the output pulses of the crank angle sensor 82.
[0028]
The surge tank 32 is provided with an intake pressure sensor 84, and an output voltage corresponding to the intake pressure PM (intake air pressure: absolute pressure) in the surge tank 32 is input to the input port 70 via the AD converter 73. ing. The cylinder block 4 of the engine 2 is provided with a water temperature sensor 86 that detects the coolant temperature THW of the engine 2 and inputs an output voltage corresponding to the coolant temperature THW to the input port 70 via the AD converter 73. . The exhaust manifold 48 is provided with an air-fuel ratio sensor 88, and an output voltage corresponding to the air-fuel ratio is input to the input port 70 via the AD converter 73.
[0029]
An on / off signal of the starter switch 89 is input to the input port 70. The starter (not shown) is turned on / off by the operation of the starter switch 89. While the starter switch 89 is being operated, the starter is turned on and the starter signal STA indicating the on state from the starter switch 89 is turned on. Is output to the input port 70.
[0030]
The output port 72 is connected to each main injector 22, sub-injector 52, negative pressure actuator 37, motor 44, electromagnetic spill valve 54 d, and igniter 92 via a corresponding drive circuit 90, and each device 22, 52, 37. , 44, 54d, and 92 are controlled as necessary.
[0031]
Next, fuel injection control for the main injector 22 performed after the engine 2 has been started will be described.
During the warm-up of the engine 2 whose cooling water temperature THW is lower than a predetermined temperature after the start is completed, an amount of fuel corresponding to a later-described stoichiometric air-fuel ratio basic fuel injection amount QBS is injected into the intake stroke to perform homogeneous combustion. After that, when the coolant temperature THW becomes higher than the predetermined temperature and the warm-up of the engine 2 is completed, the operating state of the engine 2 is determined by an engine speed NE detected by the crank angle sensor 82 and a lean fuel injection amount QL described later. The fuel injection amount and the fuel injection timing are controlled according to which one of the three operation regions R1, R2, and R3 determined as shown in FIG.
[0032]
Next, control of the fuel injection amount and fuel injection timing in the three operation regions R1, R2, and R3 will be described.
First, the lean fuel injection amount QL, which is the fuel injection amount in the operation regions R1, R2, is calculated based on the depression amount (accelerator opening) ACCP of the accelerator pedal 74 and the engine speed NE. The lean fuel injection amount QL is an optimum fuel injection amount for setting the output torque as the required torque when stratified combustion is performed. The lean fuel injection amount QL is obtained in advance by experiment, and the accelerator opening ACCP and the engine speed NE are set as parameters. Is stored in the ROM 66.
[0033]
As shown in FIG. 6, in the operation region R1 where the lean fuel injection amount QL is smaller than the threshold value QQ1, an amount of fuel corresponding to the lean fuel injection amount QL is injected at the end of the compression stroke. The fuel injected by the injection at the end of the compression stroke travels into the recess 24 of the piston 6 and then collides with the peripheral wall surface 26 of the recess 24. The fuel colliding with the peripheral wall surface 26 moves while being vaporized, and a combustible air-fuel mixture layer is formed in the recess 24 in the vicinity of the spark plug 20. Then, the stratified combustible mixture is ignited by the spark plug 20 so that stratified combustion is performed.
[0034]
In the operation region R2 where the lean fuel injection amount QL is between the threshold value QQ1 and the threshold value QQ2, the amount of fuel corresponding to the lean fuel injection amount QL is divided into an intake stroke and an end of the compression stroke. Spray. That is, the first fuel injection is performed during the intake stroke, and then the second fuel injection is performed at the end of the compression stroke. The first injected fuel flows into the combustion chamber 10 together with the intake air, and a homogeneous lean mixture is formed in the entire combustion chamber 10 by the injected fuel. Further, as a result of the fuel injection being performed at the end of the compression stroke, a combustible air-fuel mixture layer is formed in the recess 24 near the spark plug 20 as described above. The layered combustible air-fuel mixture is ignited by the spark plug 20, and the lean air-fuel mixture occupying the entire combustion chamber 10 is combusted by the ignition flame. That is, in the operation region R2, stratified combustion with a lower stratification degree than that in the operation region R1 described above is performed.
[0035]
On the other hand, in the operation region R3 where the lean fuel injection amount QL is larger than the threshold value QQ2, an amount of fuel corresponding to the stoichiometric air-fuel ratio basic fuel injection amount QBS is injected into the intake stroke to perform homogeneous combustion. The stoichiometric air-fuel ratio basic fuel injection amount QBS is a fuel injection amount necessary for setting the air-fuel ratio to the stoichiometric air-fuel ratio. 7 is stored in the ROM 66 in the form of a map shown in FIG. 7 using the intake pressure PM in the tank 32 and the engine speed NE as parameters.
[0036]
Next, fuel injection control of the main injector 22 and the sub-injector 52 in the control executed by the ECU 60 in the first embodiment will be described. FIG. 8 shows a flowchart of a fuel injection control process for the main injector 22. This process is a process repeatedly executed at a preset cycle. The steps in the flowchart are represented by “S˜”.
[0037]
When the fuel injection control process is started, first, each detection data (cooling) representing the operating state of the engine 2 obtained from the detection of each sensor 46a, 50a, 76, 80, 82, 84, 86, 88, 89. Water temperature THW, fuel pressure PF, starter signal STA, engine speed NE, etc.) are read (S110).
[0038]
Next, the ECU 60 determines whether or not the engine speed NE is greater than or equal to the first determination value NE1 (S120). Here, the first determination value NE1 is a value for determining whether or not the engine 2 is in a starting state, and in the first embodiment, NE1 = 400 rpm. Here, if the engine speed NE is equal to or higher than the first determination value NE1, it means that the engine 2 has been started. If NE ≧ NE1 (“YES” in S120), the starting state determination flag FSC is set to “0” (S130).
[0039]
If it is immediately after the starter is turned on and NE <NE1 (“NO” in S120), then the ECU 60 determines whether or not the engine speed NE is equal to or less than the second determination value NE2 (S140). . Here, the second determination value NE2 is provided for hysteresis, and in the first embodiment, NE2 = 200 rpm. If the engine speed NE is still low and NE ≦ NE2 (“YES” in S140), the start state determination flag FSC indicating that the engine is starting is set to “1” (S150).
[0040]
Next, it is determined whether or not the starting state determination flag FSC is “1” (S160). When the start is completed and the start state determination flag FSC is set to “0” (“NO” in S160), the ECU 60 performs the fuel injection control after the start is completed (S210), and performs this process. Exit once. If the start-up has not been completed (“YES” in S160), it is next determined whether or not the fuel pressure PF detected by the fuel pressure sensor 50a is equal to or higher than the reference pressure PFS (S170). Here, the reference pressure PFS is determined in the compression stroke of the engine 2 to determine whether or not there is a sufficient fuel pressure PF that allows the main injector 22 to inject fuel directly into the combustion chamber 10 and sufficiently atomize. Value.
[0041]
If PF <PFS (“NO” in S170), for example, because the rotational speed of the high-pressure pump 54 has not yet increased due to cranking, etc. (“NO” in S170), the main injector 22 enters the combustion chamber 10 during the intake stroke. An amount of fuel corresponding to the starting fuel injection amount set based on the coolant temperature THW is set to be injected (S190). If PF ≧ PFS (“YES” in S170), it is determined whether or not the cooling water temperature THW detected by the water temperature sensor 86 exceeds the reference temperature THWS (S180). Here, the reference temperature THWS is a temperature indicating that the engine 2 is in a low temperature state. If the coolant temperature THW is equal to or lower than the reference temperature THWS, it means that the engine 2 is in a low temperature state. In the first embodiment, 5 ° C. is set as the reference temperature THWS.
[0042]
If THW ≦ THWS (“NO” in S180), setting is made such that fuel is injected from the main injector 22 into the combustion chamber 10 in the intake stroke (S190). This is because it is determined that atomization is insufficient for direct fuel injection into the combustion chamber 10 during the compression stroke.
[0043]
If it is determined in step S180 that THW> THWS (“YES” in S180), the main injector 22 is set to inject fuel into the combustion chamber 10 in two steps, an intake stroke and a compression stroke. (S200). This is because it was determined in step S170 that the fuel pressure PF is sufficient to directly atomize the fuel into the combustion chamber 10 during the compression stroke and sufficiently atomize, thereby realizing stratified combustion and more stable combustion. This is to achieve the state.
[0044]
Thus, this process is temporarily terminated.
Next, fuel injection control of the sub injector 52 will be described. FIG. 9 shows a flowchart of the injection start process for the sub-injector 52. FIG. 10 shows a flowchart of the injection end process for the sub-injector 52. These processes are executed repeatedly at a preset cycle. The steps in the flowchart are represented by “S˜”.
[0045]
When the process shown in FIG. 9 is started, the ECU 60 first determines whether or not the starter signal STA is turned off or on (S310). That is, it is determined whether or not the engine 2 has been started. If it is determined that the starter signal STA has been turned on from off ("YES" in S310), it is determined whether or not the coolant temperature THW exceeds the reference temperature THWS (S320). If THW ≦ THWS (“NO” in S320), that is, if the engine 2 is in a low temperature state, then the sub-injector 52 is turned on and fuel injection from the sub-injector 52 into the surge tank 32 is started ( S330). And this process is once complete | finished.
[0046]
Thereby, when the engine 2 is at a low temperature when the engine 2 is started, fuel is injected from both the main injector 22 and the sub-injector 52, and the fuel is sufficiently atomized from the sub-injector 52. The startability is improved by supplying the fresh fuel into the combustion chamber 10.
[0047]
Next, when the process shown in FIG. 10 is started, the ECU 60 first determines whether or not the sub-injector 52 is on (S410). If the sub-injector 52 is off (“NO” in S410), it is not necessary to end the injection of the sub-injector 52, so this process is temporarily ended. If the sub-injector 52 is on (“YES” in S410), it is next determined whether or not the elapsed time from the start of injection of the sub-injector 52 is within the injection limit time (S420). This injection limit time is a time set in consideration of the fact that the start has not been completed for some reason. If the injection limit time has elapsed (“NO” in S420), the sub-injector 52 is immediately turned off. (S440), fuel injection from the sub-injector 52 is stopped. This injection restriction time is set so that the injection restriction time becomes longer as the cooling water temperature THW becomes lower according to the cooling water temperature THW according to the map as shown in FIG.
[0048]
If the injection limit time has not elapsed ("YES" in S420), the specified rotational speed STJNE is calculated according to the coolant temperature THW (S425). As shown in FIG. 11, a map of the prescribed rotational speed STJNE with the cooling water temperature THW as a parameter is stored in the ROM 66 in advance. From this map, the specified rotational speed STJNE is calculated according to the coolant temperature THW.
[0049]
In the map of the prescribed rotational speed STJNE shown in FIG. 11, when the coolant temperature THW is −10 ° C. or lower, the prescribed rotational speed STJNE is set higher than 0 ° C. to 5 ° C. In the region of 0 ° C. to −10 ° C., the specified rotational speed STJNE increases linearly as the temperature becomes lower. For example, when the cooling water temperature THW is −10 ° C. or less, the specified rotational speed STJNE = 1000 rpm, and when the cooling water temperature THW is 0 ° C. to 5 ° C., the specified rotational speed STJNE = 400 rpm.
[0050]
Next, it is determined whether or not the engine speed NE has become equal to or higher than the specified speed STJNE (S430). If NE <STJNE (“NO” in S430), the process is temporarily terminated. If NE ≧ STJNE (“YES” in S430), the sub-injector 52 is turned off (S440), and fuel injection from the sub-injector 52 is stopped. Thus, the injection of the sub-injector 52 at the current start is completed.
[0051]
Thus, in the first embodiment, since STJNE = 400 rpm at 0 ° C. to 5 ° C., fuel injection from the sub-injector 52 is completed simultaneously with the completion of the start (NE ≧ NE1). However, as the temperature becomes lower in the temperature region below 0 ° C., STJNE increases away from 400 rpm, so that the fuel injection from the sub-injector 52 continues beyond the point in time when it is determined that the start is completed. Particularly at -10 ° C. or lower, the sub-injector 52 stops the injection most slowly.
[0052]
An example of the control when the coolant temperature THW is −10 ° C. or lower is shown in the timing chart of FIG. Cranking is started at time t0, and when the engine speed NE becomes NE1 (400 rpm) or more at time t1, the start is completed, and the fuel injection of the main injector 22 shifts to the fuel injection after the start is completed. However, the sub-injector 52 continues until time t2 when the engine speed NE becomes 1000 rpm or more, and the engine speed is stable as shown by the solid line.
[0053]
In FIG. 12, the broken line shows the transition of the engine speed NE when the fuel injection of the sub-injector 52 is stopped at the time t <b> 1 when the start is completed. In this way, if the fuel injection of the sub-injector 52 is stopped at the time point (t1) when the start is completed in the low temperature state, the subsequent combustion becomes unstable and the engine speed NE does not increase smoothly. For this reason, after the start is completed, the engine speed NE may be reduced to cause an engine stall. Further, since the engine speed NE does not increase smoothly, there is a risk that various controls using the engine speed NE as a parameter will be adversely affected.
[0054]
In the configuration described above, the main injector 22 corresponds to the main fuel injection valve, the sub-injector 52 corresponds to the auxiliary fuel injection valve, and the water temperature sensor 86 corresponds to the engine temperature detecting means. Further, step S425 corresponds to the processing as the specified rotational speed setting means, and steps S330, S420, S430, and S440 correspond to the processing as the auxiliary fuel injection control means.
[0055]
According to the first embodiment described above, the following effects can be obtained.
(I). If the start of the engine 2 is completed (“NO” in S160), the fuel injection from the sub-injector 52 is not stopped immediately, but until the engine speed exceeds the specified speed STJNE (“YES” in S430). The injection continues. The specified rotational speed STJNE is higher than the first determination value NE1 for determining completion of starting, and is set higher on the lower side of the coolant temperature THW representing the temperature of the engine 2 than on the higher side. Therefore, even after the start is completed, the injection of the sub-injector 52 is continued and the sufficiently atomized fuel is supplied to the combustion chamber 10. In addition, the lower the temperature, the longer the fuel injection from the sub-injector 52 continues. Therefore, even if the temperature is extremely low, the rotation of the engine 2 is stabilized and a smooth increase in the number of revolutions can be realized.
[0056]
Therefore, effects such as prevention of engine stall and prevention of adverse effects on various controls using the rotation speed as a parameter can be produced regardless of the degree of low temperature.
[Other embodiments]
The temperature of the engine 2 is determined by the cooling water temperature THW detected by the water temperature sensor 86. In addition to this, an oil temperature sensor that detects the temperature of the lubricating oil of the engine 2 is provided, and the temperature of the lubricating oil From this, the temperature of the engine 2 may be determined.
[0057]
In the first embodiment, the sub-injector 52 is used only at the time of cold start, but in addition to this, it may be used to generate a homogeneous mixture during weak stratified combustion after the start is completed. That is, instead of fuel injection in the intake stroke by the main injector 22, the fuel may be injected into the surge tank 32 from the sub-injector 52.
[0058]
Although the embodiments of the present invention have been described above, the embodiments of the present invention include embodiments of various technical items as described below in addition to the technical items described in the claims. It is noted that there is.
[0059]
(1). In addition to the configuration of claim 3,
Time limit setting means for setting the time limit according to the temperature of the internal combustion engine detected by the engine temperature detection means and for setting the time limit longer on the low temperature side of the internal combustion engine than on the high side. A fuel injection control device for an in-cylinder injection internal combustion engine.
[0060]
(2). The cylinder according to any one of claims 1 to 3, wherein the specified rotational speed is set in a range of a value equal to or greater than a rotational speed determination value for determining completion of starting of the internal combustion engine. A fuel injection control device for an internal injection internal combustion engine.
[0061]
(3). The fuel injection control device for a direct injection internal combustion engine according to any one of claims 1 to 3, wherein the fuel is injected from the auxiliary fuel injection valve only at a low temperature start time. .
[0062]
【The invention's effect】
In the fuel injection control device for a direct injection internal combustion engine according to claim 1, when the start of the internal combustion engine is completed, the fuel injection from the auxiliary fuel injection valve is not stopped immediately, but the rotational speed of the internal combustion engine is defined. The injection is continued until the rotational speed is exceeded. The prescribed rotational speed is set higher on the low temperature side of the internal combustion engine than on the high temperature side. For this reason, even after the start is completed, sufficiently atomized fuel is supplied to the combustion chamber. In addition, the lower the temperature, the longer the fuel injection from the auxiliary fuel injection valve continues. Therefore, even if the temperature is extremely low, the rotation of the internal combustion engine is stabilized and a smooth increase in the number of revolutions can be realized. . Therefore, effects such as prevention of engine stall and prevention of adverse effects on various controls using the rotation speed as a parameter can be derived regardless of the degree of low temperature.
[0063]
The fuel injection control device for a direct injection internal combustion engine according to claim 2 may be configured to include an engine temperature detecting means, a specified rotational speed setting means, and an auxiliary fuel injection control means. Here, when the auxiliary fuel injection control means injects the fuel from the auxiliary fuel injection valve, the auxiliary fuel injection control means starts from the auxiliary fuel injection valve until the rotational speed of the internal combustion engine exceeds the specified speed set by the specified speed setting means. The fuel injection continues. This prescribed rotational speed is set higher by the prescribed rotational speed setting means on the low temperature side of the internal combustion engine than on the high temperature side. Therefore, similarly to the first aspect, the rotation of the internal combustion engine is stabilized regardless of the low temperature level, and a smooth increase in the number of revolutions can be realized.
[0064]
According to a third aspect of the present invention, in the fuel injection control device for a cylinder injection type internal combustion engine, in contrast to the second aspect, the auxiliary fuel injection control means is configured such that the rotational speed of the internal combustion engine exceeds the specified rotational speed. In addition, when the duration of fuel injection by the auxiliary fuel injection valve exceeds the limit time, the fuel injection by the auxiliary fuel injection valve is stopped. Considering that the start was not completed for some reason, if the fuel injection duration by the auxiliary fuel injection valve exceeds the time limit, the auxiliary fuel injection control means stops the fuel injection by the auxiliary fuel injection valve. ing. Thus, together with the effect of the second aspect, unnecessary fuel injection can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an in-vehicle gasoline engine and a control system thereof according to a first embodiment.
FIG. 2 is a plan sectional view of the cylinder head according to the first embodiment.
FIG. 3 is a plan view of a piston top surface in the first embodiment.
4 is a cross-sectional view taken along line XX in FIG.
5 is a YY cross-sectional view in FIG. 2. FIG.
FIG. 6 is an explanatory diagram of an operation region after the start is completed in the first embodiment.
7 is an explanatory diagram of a map for obtaining a theoretical air-fuel ratio basic fuel injection amount QBS after completion of starting in Embodiment 1. FIG.
FIG. 8 is a flowchart of fuel injection control processing in the first embodiment.
FIG. 9 is a flowchart of sub-injector injection start processing in the first embodiment.
10 is a flowchart of sub-injector injection end processing in Embodiment 1. FIG.
FIG. 11 is a configuration explanatory diagram of a map of a prescribed rotational speed STJNE using the coolant temperature THW as a parameter in the first embodiment.
12 is a timing chart showing an example of control in Embodiment 1. FIG.
FIG. 13 is a configuration explanatory diagram of a map of an injection limitation time with the coolant temperature THW as a parameter in the first embodiment.
[Explanation of symbols]
2 ... Engine, 2a ... Cylinder, 4 ... Cylinder block, 6 ... Piston, 8 ... Cylinder head, 10 ... Combustion chamber, 12a ... First intake valve, 12b ... Second intake valve, 14a ... First intake port, 14b ... Second intake port, 16 ... exhaust valve, 18 ... exhaust port, 20 ... spark plug, 22 ... main injector, 24 ... recess, 26 ... peripheral wall surface, 30 ... intake manifold, 30a ... first intake passage, 30b ... second Intake passage, 32 ... surge tank, 34 ... airflow control valve, 36 ... shaft, 37 ... negative pressure actuator, 40 ... intake duct, 42 ... air cleaner, 44 ... motor, 46 ... throttle valve, 46a ... throttle opening sensor, 48 ... exhaust manifold, 50 ... fuel distribution pipe, 50a ... fuel pressure sensor, 52 ... sub-injector, 54 ... high pressure pump, 54a ... high pressure fuel passage, 5 4b ... Check valve, 54c ... Low pressure fuel passage, 54d ... Electromagnetic spill valve, 56 ... Fuel tank, 58 ... Low pressure pump, 60 ... Electronic control unit (ECU), 62 ... Bidirectional bus, 64 ... RAM, 66 ... ROM, 68 ... CPU, 70 ... input port, 72 ... output port, 73 ... AD converter, 74 ... accelerator pedal, 76 ... accelerator opening sensor, 80 ... top dead center sensor, 82 ... crank angle sensor, 84 ... suction Barometric pressure sensor, 86 ... water temperature sensor, 88 ... air-fuel ratio sensor, 89 ... starter switch, 90 ... drive circuit, 92 ... igniter.

Claims (3)

A main fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine, and an auxiliary fuel injection valve for injecting fuel into an intake manifold of an internal combustion engine, at the time of cold start, the fuel injection by the main fuel injection valve, A fuel injection control device for a direct injection internal combustion engine that temporarily executes fuel injection by the auxiliary fuel injection valve in order to compensate for a shortage caused by deterioration of atomization of fuel injected from the main fuel injection valve,
When injecting fuel from the auxiliary fuel injection valve, the injection is continued until the rotational speed of the internal combustion engine exceeds a specified rotational speed that is equal to or higher than a rotational speed determination value for determining completion of startup of the internal combustion engine, and the temperature of the internal combustion engine is increased. A fuel injection control device for a direct injection internal combustion engine, wherein the prescribed rotational speed is set higher on a low side than on a high side. A main fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine, and an auxiliary fuel injection valve for injecting fuel into an intake manifold of an internal combustion engine, at the time of cold start, the fuel injection by the main fuel injection valve, A fuel injection control device for a direct injection internal combustion engine that temporarily executes fuel injection by the auxiliary fuel injection valve in order to compensate for a shortage caused by deterioration of atomization of fuel injected from the main fuel injection valve,
Engine temperature detection means for detecting the temperature of the internal combustion engine;
In accordance with the temperature of the internal combustion engine detected by the engine temperature detection means, a specified rotational speed that is equal to or higher than the rotational speed determination value for determining completion of starting of the internal combustion engine is set, and higher on the low temperature side of the internal combustion engine A prescribed rotational speed setting means for setting the prescribed rotational speed high compared to the side;
When fuel is injected from the auxiliary fuel injection valve, fuel injection from the auxiliary fuel injection valve is continued until the engine speed exceeds the specified engine speed set by the specified engine speed setting means. Auxiliary fuel injection control means;
A fuel injection control device for a direct injection internal combustion engine.   The auxiliary fuel injection control means, when the fuel injection continuation time by the auxiliary fuel injection valve exceeds the time limit before the rotational speed of the internal combustion engine exceeds the specified rotational speed, the fuel by the auxiliary fuel injection valve The fuel injection control device for a direct injection internal combustion engine according to claim 2, wherein the injection is stopped.

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