JP3622588B2 - Fuel injection control device for diesel engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for a diesel engine.
[0002]
[Prior art]
In general, for example, in an in-vehicle diesel engine, a basic injection amount is calculated based on an accelerator pedal depression amount (accelerator depression amount) and an engine speed, and an amount of fuel corresponding to the final injection amount obtained from the basic injection amount is calculated. Inject into the combustion chamber. By performing the fuel injection in this way, the fuel is combusted in the combustion chamber, and the engine output according to the driver's request can be obtained by this combustion energy.
[0003]
It is also known to install a turbocharger in the intake / exhaust system of a diesel engine in order to increase the engine output of the diesel engine. This turbocharger is operated by exhaust gas from a diesel engine and forcibly sends air into a combustion chamber. By forcibly sending air into the combustion chamber in this way, a large amount of fuel can be injected and supplied. As a result, the combustion energy when the fuel burns increases and the engine output is improved.
[0004]
By the way, the amount of air (oxygen) sucked into the combustion chamber varies depending on various parameters such as the supercharging pressure of air by the turbocharger. Therefore, depending on these parameters, the amount of injected fuel becomes excessively large with respect to the air (oxygen) sent into the combustion chamber, and there is a possibility that black smoke is generated in the exhaust. As a device for suppressing the generation of such black smoke, for example, a fuel injection device described in JP-A-8-303271 is known.
[0005]
In the fuel injection device described in the publication, based on various parameters (supercharging pressure, etc.) that affect the generation of black smoke as described above, the maximum injection amount that can allow the generation of the black smoke is allowed. Is calculated. Then, the maximum injection amount is compared with the basic injection amount obtained based on the accelerator depression amount and the engine speed described above, and the smallest one is set as the final injection amount. By performing fuel injection based on the final injection amount calculated in this way, it is possible to suppress the amount of fuel injected with respect to the air sent into the combustion chamber from excessively increasing and generating black smoke in the exhaust. It becomes like this.
[0006]
[Problems to be solved by the invention]
In addition, in a diesel engine to which a turbocharger is attached, the number of revolutions of the turbocharger varies depending on various parameters such as atmospheric pressure and outside air temperature. Depending on these parameters, the number of revolutions of the turbocharger may be excessively high. is there. Therefore, in the fuel injection control device described in the above publication, it is conceivable to set the maximum injection amount calculated based on a parameter (such as a supercharging pressure) that affects black smoke in the exhaust gas to a small value. In this case, as the fuel injection amount is limited by the maximum injection amount for suppressing black smoke, an increase in the rotational speed of the turbocharger is suppressed, and thereby a parameter (atmospheric pressure) that affects the rotational speed. , The outside air temperature, etc.) can be prevented from becoming higher than the upper limit value.
[0007]
However, in the case where the maximum injection amount is set to be small as described above and the increase in the rotation speed of the turbocharger is suppressed, even when the rotation speed has a margin with respect to the upper limit value, the above-mentioned for suppressing black smoke When the fuel injection amount is limited by the maximum injection amount, an increase in the rotational speed is excessively suppressed. If the increase in the rotational speed of the turbocharger is excessively suppressed in this way, the engine output of the diesel engine is unnecessarily reduced.
[0008]
The present invention has been made in view of such circumstances, and its purpose is to accurately suppress an excessive increase in the rotational speed of the turbocharger and to suppress an unnecessary decrease in engine output. It is an object of the present invention to provide a fuel injection control device for a diesel engine that can be used.
[0009]
[Means for Solving the Problems]
In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, the invention according to claim 1 provides:It has a turbocharger that supercharges the air supplied to the combustion chamber of the diesel engine,Calculation of basic injection amount to obtain required engine output based on engine operating conditionsBased on the final injection amount obtained from the basic injection amountIn a fuel injection control device for a diesel engine that performs fuel injection,Based on the engine speed of the diesel engine, the air supercharging pressure by the turbocharger, and the intake air temperature of the diesel engine, a first maximum injection amount that is the maximum fuel injection amount that can allow the black smoke is Based on the first maximum injection amount calculation means for calculating, the engine speed, the atmospheric pressure, and the outside air temperature, the second maximum injection amount that is the fuel injection amount when the turbocharger speed reaches the upper limit value A second maximum injection amount calculating means for calculating the final injection amount with the smallest injection amount among the basic injection amount, the first maximum injection amount, and the second maximum injection amount as the final injection amount. With calculation meansEquipped with.
[0011]
In the invention of claim 2, in the invention of claim 1,The first maximum injection amount calculating means calculates the first maximum injection amount as a smaller value as the supercharging pressure becomes lower.
[0013]
In invention of Claim 3,In the first or second aspect of the present invention, the first maximum injection amount calculating means calculates the first maximum injection amount as a smaller value as the intake air temperature becomes higher.
[0015]
In invention of Claim 4,In the invention according to any one of claims 1 to 3, the second maximum injection amount calculating means calculates the second maximum injection amount as a smaller value as the atmospheric pressure decreases.
[0017]
In invention of Claim 5,In the invention according to any one of claims 1 to 4, the second maximum injection amount calculating means calculates the second maximum injection amount as a smaller value as the outside air temperature becomes higher.
[0026]
Parameters such as engine speed, supercharging pressure, and intake air temperature affect black smoke in the exhaust of the diesel engine, and parameters such as engine speed, atmospheric pressure, and outside air temperature affect the speed of the turbocharger.Invention of Claims 1-5The first maximum injection amount is calculated based on the parameter affecting the black smoke, and the second maximum injection amount is calculated based on the parameter affecting the rotation speed of the turbocharger. Among the first and second maximum injection amounts and the basic injection amount, the smallest one is set as the final injection amount. Therefore, when suppressing black smoke, the first maximum injection amount is made small and the first maximum injection amount is set as the final injection amount, and when suppressing the increase in the rotation speed of the turbocharger, the second maximum injection amount is set. The maximum injection amount is reduced and the second maximum injection amount is set as the final injection amount. As described above, the suppression of black smoke and the suppression of the increase in turbocharger speed are performed separately by limiting the fuel injection amount by the first and second maximum injection amounts, respectively. However, the increase in the rotational speed is not excessively suppressed by limiting the fuel injection amount for suppressing black smoke. Therefore, it is possible to prevent the engine output from being unnecessarily lowered while accurately suppressing an excessive increase in the rotational speed of the turbocharger.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an automotive diesel engine will be described with reference to FIGS.
[0028]
As shown in FIG. 1, a piston 12 is provided in a cylinder block 11 a of the diesel engine 11 so as to be able to reciprocate. The piston 12 is connected to a crankshaft 14 via a connecting rod 13. The reciprocating movement of the piston 12 is converted into rotation of the crankshaft 14 by the connecting rod 13.
[0029]
In the diesel engine 11, a cylinder head 15 is provided at the upper end of the cylinder block 11 a, and a combustion chamber 16 is provided between the cylinder head 15 and the piston 12. The cylinder block 11 a is provided with an injection nozzle 20 for injecting fuel into the combustion chamber 16, and an intake passage 32 and an exhaust passage 33 are connected to the combustion chamber 16.
[0030]
The upstream portion of the intake passage 32 and the downstream portion of the exhaust passage 33 are each connected to a turbocharger 35. The turbocharger 35 is connected to a compressor wheel 36 for sending air to the downstream side of the intake passage 32, a turbine wheel 37 rotated by exhaust gas passing through the exhaust passage 33, and the wheels 36 and 37 so as to be integrally rotatable. And a rotor shaft 38.
[0031]
The intake passage 32 is provided with an intake air temperature sensor 17 for detecting the temperature of the air that passes through the passage 32 and is sucked into the combustion chamber 16. Further, a pressure sensor 19 is connected to the intake passage 32 via a vacuum switching valve (VSV) 18. The VSV 18 performs a switching operation so that the pressure sensor 19 communicates with the intake passage 32 side or is released to the atmosphere side. By the switching operation of the VSV 18, the pressure detection target by the pressure sensor 19 is selectively switched between the atmospheric pressure and the pressure in the intake passage 32.
[0032]
On the other hand, the crankshaft 14 of the diesel engine 11 is connected to the drive shaft 41 a of the fuel injection pump 41. The fuel injection pump 41 is connected to the injection nozzle 20 of the cylinder head 15 via a fuel line 42. The fuel injection pump 41 is driven by the rotation of the crankshaft 14 being transmitted to the drive shaft 41a, and sucks fuel from a fuel tank (not shown) of the automobile and directs the fuel toward the injection nozzle 20. Discharge. The injection nozzle 20 is operated by the pressure of the fuel fed from the fuel injection pump 41 and injects the fuel into the combustion chamber 16.
[0033]
The fuel injection pump 41 includes a rotation speed sensor 45 for detecting the rotation speed of the diesel engine 11 and an electromagnetic spill valve 43 for adjusting the amount of fuel discharged toward the injection nozzle 20. The rotation speed sensor 45 outputs a signal corresponding to the rotation of the drive shaft 41 a of the fuel injection pump 41, that is, the rotation of the crankshaft 14. The electromagnetic spill valve 43 is used to adjust the amount of fuel injected from the injection nozzle 20 into the combustion chamber 16 by adjusting the amount of fuel discharged toward the injection nozzle 20.
[0034]
The fuel injection amount from the injection nozzle 20 is determined based on the depression amount (accelerator depression amount) of the accelerator pedal 25 provided in the interior of the automobile. That is, when the accelerator pedal 25 is depressed by a predetermined amount by the driver of the automobile, the accelerator depression amount at this time is detected by the accelerator position sensor 26. It means that the output of the required diesel engine 11 is high, so that this detected accelerator depression amount etc. become large. The electromagnetic spill valve 43 is driven and controlled based on the accelerator depression amount or the like so that the required output of the diesel engine 11 is obtained, and the amount of fuel corresponding to the required output is controlled by the electromagnetic spill valve 43. Is injected from the injection nozzle 20 into the combustion chamber 16.
[0035]
In such a diesel engine 11, air is sucked into the combustion chamber 16 through the intake passage 32 when the piston 12 descends during the intake stroke, and the air within the combustion chamber 16 is compressed when the piston 12 rises during the compression stroke. . In this state, fuel is injected from the injection nozzle 20 toward the high-pressure air in the combustion chamber 16, and the injected fuel self-ignites and burns, so that the piston 12 descends and moves to the expansion stroke. Due to this expansion stroke, the diesel engine 11 gains a driving force, and in the subsequent exhaust stroke, the exhaust is sent to the exhaust passage 33 by the rise of the piston 12.
[0036]
Exhaust gas sent from the combustion chamber 16 to the exhaust passage 33 is blown to the turbine wheel 37 of the turbocharger 35. The turbine wheel 37 rotates by blowing exhaust gas, and the rotation of the wheel 37 is transmitted to the compressor wheel 36 via the rotor shaft 38. When the compressor wheel 36 rotates in this way, air is forcibly sent toward the downstream side of the intake passage 32 and the amount of air taken into the combustion chamber 16 increases. When air is forcibly sent into the combustion chamber 16 in this way, a larger amount of fuel can be injected than usual, and the output of the diesel engine 11 is improved.
[0037]
A bypass passage 51 and a waste gate valve 52 are provided in the exhaust passage 33 in order to suppress an excessive increase in the supercharging pressure of the air sent into the combustion chamber 16 by the turbocharger 35. The bypass passage 51 bypasses the turbine wheel 37 and is connected to the exhaust passage 33. A waste gate valve 52 is provided in the bypass passage 51, and the bypass passage 51 is communicated and blocked by opening and closing the waste gate valve 52. When the waste gate valve 52 is opened, a part of the exhaust gas flowing through the exhaust passage 33 passes through the bypass passage 51, so that the amount of exhaust gas blown to the turbine wheel 37 is reduced and the supercharging pressure is excessively increased. The rise will be suppressed.
[0038]
Next, the electrical configuration of the fuel injection control device in the present embodiment will be described.
The fuel injection control device includes an electronic control unit (hereinafter referred to as ECU) 92 for controlling the operating state of the diesel engine 11. The ECU 92 is configured as an arithmetic logic circuit including a ROM, a CPU, a RAM, a backup RAM, and the like.
[0039]
Here, the ROM is a memory in which various control programs and maps that are referred to when executing these various control programs are stored, and the CPU performs arithmetic processing based on the various control programs and maps stored in the ROM. Execute. The RAM is a memory that temporarily stores calculation results from the CPU, data input from each sensor, and the like. The backup RAM is a non-volatile memory that stores data to be saved when the diesel engine 11 is stopped. It is.
[0040]
The ECU 92 is connected to the atmospheric temperature sensor 46 for detecting the atmospheric temperature, the intake air temperature sensor 17, the pressure sensor 19, the accelerator position sensor 26, the rotational speed sensor 45, the electromagnetic spill valve 43, the VSV 18, and the like. ing.
[0041]
The ECU 92 configured as described above calculates the engine speed NE based on the detection signal from the rotation speed sensor 45, and calculates the accelerator depression amount ACCP based on the detection signal from the accelerator position sensor 26. Then, the basic injection amount Qbse is calculated with reference to the map of FIG. 3 based on the engine speed NE and the accelerator depression amount ACCP. The basic injection amount Qbse increases as the accelerator depression amount ACCP increases. The diesel engine 11 is driven by injecting fuel into the combustion chamber 16 by controlling the driving of the electromagnetic spill valve 43 based on the basic injection amount Qbse.
[0042]
By the way, when the amount of fuel injected into the combustion chamber 16 becomes excessive with respect to the amount of air (oxygen) fed into the combustion chamber 16, black smoke is generated in the exhaust. Therefore, the first maximum injection amount QfullO, which is the maximum value of the fuel injection amount that can allow the black smoke, is calculated based on various parameters that affect the black smoke in the exhaust (the amount of oxygen in the combustion chamber 16). The actual fuel injection amount is prevented from becoming larger than the first maximum injection amount QfullO. By thus limiting the fuel injection amount with the first maximum injection amount QfullO, the generation of the black smoke can be suppressed.
[0043]
The parameters affecting the black smoke in the exhaust include the engine speed NE, the supercharging pressure PIM by the turbocharger 35, the intake air temperature THAi, and the like. This is because the amount of air taken into the combustion chamber 16 changes due to changes in the engine speed NE and the supercharging pressure PIM, and the density of air drawn into the combustion chamber 16 changes due to changes in the intake air temperature THAi. This is because the oxygen amount in the combustion chamber 16 changes due to these changes.
[0044]
The intake air temperature THAi is obtained based on a detection signal from the intake air temperature sensor 17. The supercharging pressure PIM is obtained based on a detection signal from the pressure sensor 19. The ECU 92 drives and controls the VSV 18 to switch the pressure detection target by the pressure sensor 19 between the pressure in the intake passage 32 and the atmospheric pressure. For example, the pressure sensor 19 is released to the atmosphere when the diesel engine 11 is started or idling, and the pressure sensor 19 is communicated with the intake passage 32 at other times. Then, the ECU 92 calculates the atmospheric pressure PA based on the detection signal of the sensor 19 when the pressure sensor 19 is released to the atmosphere, and the ECU 92 of the sensor 19 when the pressure sensor 19 communicates with the intake passage 32. An intake pressure PM is calculated based on the detection signal. Based on the atmospheric pressure PA and the intake pressure PM thus calculated, the ECU 92 calculates a supercharging pressure PIM by the turbocharger 35.
[0045]
Further, in the diesel engine 11 to which the turbocharger 35 is attached, it is necessary to prevent the rotational speed of the turbocharger 35 from becoming excessively high. Although the rotational speed of the turbocharger 35 is affected by various parameters, the rotational speed of the turbocharger 35 may become excessively high depending on the state of these parameters, and it is necessary to suppress an excessive increase in the rotational speed. Become.
[0046]
Parameters that affect the rotational speed of the turbocharger 35 include the engine rotational speed NE, the atmospheric pressure PA, and the outside air temperature THAo. The engine speed NE affects the speed of the turbocharger 35 because the amount of exhaust gas blown to the turbine wheel 37 changes as the engine speed NE changes. Further, when the atmospheric pressure PA changes, the compressor pre-pressure that is upstream of the compressor wheel 36 of the turbocharger 35 and the turbine post-pressure that is downstream of the turbine wheel 37 of the turbocharger 35 change. The rotational speed of the turbocharger 35 at a certain supercharging pressure PIM regulated by the waste gate valve 52 is changed by the change of the compressor front pressure, and the pressure difference between the front and rear of the turbine wheel 37 is changed by the change of the turbine rear pressure. It changes and the ease of the rotation rise of the turbocharger 35 changes. As described above, the atmospheric pressure PA affects the rotational speed of the turbocharger 35. Further, when the outside air temperature THAo changes, the energy of the exhaust sent to the exhaust passage 33 changes, and the rotational speed of the turbocharger 35 driven by this exhaust also changes. Thus, the change in the outside air temperature THAo also affects the rotational speed of the turbocharger 35.
[0047]
It is also conceivable to set the first maximum injection amount QfullO described above to be small so that the rotation speed of the turbocharger 35 does not become excessively high due to changes in various parameters as described above. In this case, when the fuel injection amount is limited by the first maximum injection amount QfullO in order to suppress black smoke, an increase in the rotational speed of the turbocharger 35 is suppressed in accordance with the limitation, and based on changes in the various parameters. It can suppress that the rotation speed becomes higher than an upper limit value.
[0048]
However, when the first maximum injection amount QfullO is set to be small as described above and the increase in the rotational speed of the turbocharger 35 is suppressed, the first When the fuel injection amount for black smoke suppression is restricted by the maximum injection amount QfullO, the increase in the rotational speed is excessively suppressed. If the increase in the rotational speed of the turbocharger 35 is excessively suppressed in this way, the engine output of the diesel engine 11 will unnecessarily decrease.
[0049]
Therefore, in the present embodiment, based on various parameters that affect the rotational speed of the turbocharger 35 in addition to the first maximum injection amount QfullO, the second fuel injection amount when the rotational speed reaches the upper limit value is set. The maximum injection amount QfullJ is calculated. Then, the second maximum injection amount QfullJ is compared with the basic injection amount Qbse and the first maximum injection amount QfullO described above, and the smallest of these is set as the final injection amount Qfin. Based on the final injection amount Qfin thus calculated, the electromagnetic spill valve 43 of the fuel injection pump 41 is driven and controlled, and an amount of fuel corresponding to the final injection amount Qfin is injected from the injection nozzle 20 into the combustion chamber 16.
[0050]
Therefore, when black smoke is to be suppressed, the first maximum injection amount QfullO is smaller than the other injection amounts Qbse QfullJ, and the first maximum injection amount QfullO becomes the final injection amount Qfin. By performing fuel injection into the combustion chamber 16 based on this final injection amount Qfin, black smoke in the exhaust can be accurately suppressed.
[0051]
When the rotational speed of the turbocharger 35 is to be suppressed, the second maximum injection amount QfullJ is smaller than the other injection amounts Qbse and QfullO, and the second maximum injection amount QfullJ becomes the final injection amount Qfin. By performing fuel injection into the combustion chamber 16 based on this final injection amount Qfin, it is possible to suppress the rotational speed of the turbocharger 35 from becoming higher than the upper limit value.
[0052]
In this way, suppression of black smoke and suppression of increase in the rotational speed of the turbocharger 35 are performed separately by limiting the fuel injection amount by the first and second maximum injection amounts QfullO and QfullJ, respectively. Therefore, it is possible to limit the fuel injection amount by the first maximum injection amount QfullO to an amount necessary for suppressing black smoke, and to limit the fuel injection amount by the second maximum injection amount QfullJ of the turbocharger 35. Only the amount necessary for suppressing the increase in the rotational speed can be achieved.
[0053]
Accordingly, when the rotational speed of the turbocharger 35 has a margin with respect to the upper limit value, when the fuel injection amount is limited by the first maximum injection amount QfullO to suppress black smoke, the rotation of the turbocharger 35 is caused by this limitation. The increase in the number is not excessively suppressed. Therefore, the fuel injection amount for suppressing the black smoke by the first maximum injection amount QfullO is suppressed while suppressing the rotation speed of the turbocharger 35 from being excessively high due to the restriction of the fuel injection amount by the second maximum injection amount QfullJ. When this restriction is performed, it is possible to prevent an increase in the rotational speed of the turbocharger 35 from being excessively suppressed and unnecessarily lowering the engine output.
[0054]
Next, the procedure for calculating the final injection amount Qfin will be described with reference to FIG. FIG. 2 is a flowchart showing a final injection amount calculation routine for calculating the final injection amount Qfin. The final injection amount calculation routine is executed through the ECU 92 by, for example, a time interruption every predetermined time.
[0055]
In the final fuel injection amount calculation routine, the basic injection amount Qbse, which is the fuel injection amount for obtaining the required engine output, is calculated in the process of step S101. Then, the first maximum injection amount QfullO used for limiting the fuel injection amount for suppressing black smoke in the process of step S102 is calculated, and the increase in the rotational speed of the turbocharger 35 is suppressed in the process of step S103. The second maximum injection amount QfullJ used for limiting the fuel injection amount is calculated. Further, in the process of step S104, a final injection amount Qfin is calculated based on the basic injection amount Qbse, the first maximum injection amount QfullO, and the second maximum injection amount QfullJ.
[0056]
In step S101, the ECU 92 calculates a basic injection amount Qbse with reference to the map of FIG. 3 based on the engine speed NE and the accelerator depression amount ACCP. The accelerator depression amount ACCP means the output of the diesel engine 11 requested by the driver, and a higher output is required as the accelerator depression amount ACCP increases. The basic injection amount Qbse is calculated as a fuel injection amount that provides the required output.
[0057]
The ECU 92 is the maximum value of the fuel injection amount that can allow the black smoke based on the parameters affecting the black smoke in the exhaust gas such as the engine speed NE, the supercharging pressure PIM, and the intake air temperature THAi as the process of step S102. A first maximum injection amount QfullO is calculated. Further, as a process of step S103, the ECU 92 reaches the upper limit value of the turbocharger 35 based on parameters affecting the rotation speed of the turbocharger 35 such as the engine speed NE, the atmospheric pressure PA, and the outside air temperature THAo. The second maximum injection amount QfullJ that is the fuel injection amount at that time is calculated.
[0058]
The ECU 92 performs the subsequent step S104 as the basic injection amount Qbse calculated in the step S101, the first maximum injection amount QfullO calculated in the step S102, and the second calculated in the step S103. Are compared with each other, and the smallest one is set as the final injection amount Qfin. Thereafter, the ECU 92 once ends this final injection amount calculation routine. When the final injection amount Qfin is calculated by the final fuel injection amount calculation routine, an amount of fuel corresponding to the final injection amount Qfin is injected into the combustion chamber 16.
[0059]
Next, the process of step S102 of the final injection amount calculation routine will be described in detail with reference to FIG. FIG. 4 is a flowchart showing a first maximum injection amount calculation routine for calculating the first maximum injection amount QfullO. The first maximum injection amount calculation routine is executed through the ECU 92 every time the process proceeds to step S102 of the final injection amount calculation routine.
[0060]
In the first maximum injection amount calculation routine, the first maximum injection amount QfullO is calculated by the following equation (1) in the process of step S204. Note that the base value QfullB, the supercharging pressure correction coefficient FP, and the intake air temperature correction coefficient FAi used in Expression (1) are calculated by the processes in steps S201 to S203.
[0061]
QfullO = QfullB · FP · FAi (1)
QfullO: first maximum injection amount
QfullB: Base value
FP: Boost pressure correction coefficient
FAi: Intake air temperature correction coefficient
As a process of step S201, the ECU 92 calculates a base value QfullB based on the engine speed NE with reference to FIG. This base value QfullB is the maximum value of the fuel injection amount that can allow black smoke at the current engine speed NE under the conditions of the standard boost pressure PIM and the intake air temperature THAi.
[0062]
In step S202, the ECU 92 calculates a supercharging pressure correction coefficient FP with reference to the map of FIG. 6 based on the engine speed NE and the supercharging pressure PIM. The supercharging pressure correction coefficient FP increases as the supercharging pressure PIM increases. After the supercharging pressure PIM becomes so high that the waste gate valve 52 needs to be opened, the supercharging pressure PIM increases. It becomes smaller value. Further, the supercharging pressure correction coefficient FP becomes smaller as the engine speed NE becomes lower when the waste gate valve 52 is not open.
[0063]
In step S203, the ECU 92 calculates the intake air temperature correction coefficient FAi with reference to the map of FIG. 7 based on the engine speed NE and the intake air temperature THAi. The intake air temperature correction coefficient FAi decreases as the intake air temperature THAi increases, and decreases as the engine speed NE decreases.
[0064]
In step S204, the ECU 92 calculates the first maximum injection amount QfullO using the above formula (1) based on the base value QfullB, the supercharging pressure correction coefficient FP, and the intake air temperature correction coefficient FAi. Return to the final injection amount calculation routine (FIG. 2). The first maximum injection amount QfullO limits the fuel injection amount for suppressing black smoke.
[0065]
The first maximum injection amount QfullO is larger than before because when the boost pressure PIM increases with the waste gate valve 52 closed, the boost pressure correction coefficient FP increases due to the change in the boost pressure PIM. Value. On the contrary, when the supercharging pressure PIM becomes low, the supercharging pressure correction coefficient FP becomes small due to the change in the supercharging pressure PIM, so the first maximum injection amount QfullO becomes a smaller value than before. This is because when the supercharging pressure PIM changes and the amount of air (oxygen) sent into the combustion chamber 16 changes, the maximum value of the fuel injection amount that can allow black smoke increases or decreases according to the oxygen amount, This is because it is preferable to increase or decrease the first maximum injection amount QfullO according to this.
[0066]
Further, the first maximum injection amount QfullO becomes a smaller value than before because the intake air temperature correction coefficient FAi becomes small due to the change in the intake air temperature THAi when the intake air temperature THAi becomes high. On the contrary, when the intake air temperature THAi is lowered, the intake air temperature correction coefficient FAi is increased due to the change in the intake air temperature THAi, and therefore the first maximum injection amount QfullO becomes a larger value than before. This is because when the intake air temperature THAi changes and the density of the air fed into the combustion chamber 16 changes, the amount of oxygen in the combustion chamber 16 also changes, and the fuel injection that allows black smoke according to the amount of oxygen. This is because the maximum value of the amount increases and decreases, and it is preferable to increase and decrease the first maximum injection amount QfullO accordingly.
[0067]
As described above, even if the oxygen amount in the combustion chamber 16 changes due to the change in the supercharging pressure PIM or the intake air temperature THAi, the correction of the first maximum injection amount QfullO by the supercharging pressure correction coefficient FP and the intake air temperature correction coefficient FAi. And the first maximum injection amount QfullO increases or decreases according to the change in the oxygen amount. By limiting the fuel injection amount with the first maximum injection amount QfullO, it is possible to accurately suppress black smoke in the exhaust regardless of changes in the supercharging pressure PIM and the intake air temperature THAi.
[0068]
Next, the process of step S103 in the final injection amount calculation routine will be described in detail with reference to FIG. FIG. 8 is a flowchart showing a second maximum injection amount calculation routine for calculating the second maximum injection amount QfullJ. The second maximum injection amount calculation routine is executed through the ECU 92 every time the process proceeds to step S103 of the final injection amount calculation routine.
[0069]
In the second maximum injection amount calculation routine, the second maximum injection amount QfullJ is calculated by the following equation (2) in the process of step S304. Note that the base value QfullF, the atmospheric pressure correction coefficient FPA, and the outside air temperature correction coefficient FAo used in Expression (2) are calculated by the processes in steps S301 to S303.
[0070]
QfullJ = QfullO. (1-FPA.FAo) (2)
QfullJ: second maximum injection amount
QfullF: Base value
FPA: Atmospheric pressure correction coefficient
FAo: Outside air temperature correction coefficient
As a process of step S301, the ECU 92 calculates a base value QfullF based on the engine speed NE with reference to FIG. This base value QfullF is the fuel injection amount when the rotational speed of the turbocharger 35 reaches the upper limit value under the current engine rotational speed NE under the conditions of the standard atmospheric pressure and the outside air temperature “0 ° C.”.
[0071]
As a process of step S302, the ECU 92 calculates an atmospheric pressure correction coefficient FPA with reference to the map of FIG. 10 based on the engine speed NE and the atmospheric pressure PA. The atmospheric pressure correction coefficient FPA increases as the engine speed NE increases, and increases as the atmospheric pressure PA decreases.
[0072]
In step S303, the ECU 92 calculates the outside air temperature correction coefficient FAo with reference to the map of FIG. 11 based on the engine speed NE and the outside air temperature THAo. The outside air temperature correction coefficient FAo increases as the engine speed NE increases when the engine speed NE is in the low speed region, and the engine speed NE is high when the engine speed NE is in the high speed region. The higher the value, the smaller the value.
[0073]
In step S304, the ECU 92 calculates the second maximum injection amount QfullJ using the above equation (2) based on the base value QfullF, the atmospheric pressure correction coefficient FPA, and the outside air temperature correction coefficient FAo. Return to the injection amount calculation routine (FIG. 2). The second maximum injection amount QfullJ limits the fuel injection amount for suppressing the rotation of the turbocharger 35 from becoming excessively high.
[0074]
When the atmospheric pressure PA increases, the second maximum injection amount QfullJ becomes a larger value than before because the atmospheric pressure correction coefficient FPA decreases due to the change in the atmospheric pressure PA. When the atmospheric pressure PA increases and the compressor pre-pressure, which is upstream of the compressor wheel 36 of the turbocharger 35, increases, the turbocharger 35 rotates when the supercharging pressure PIM regulated by the waste gate valve 52 is reached. Driven by exhaust gas because the difference in turbine front-rear pressure is reduced by reducing the number of turbines and the turbine post pressure, which is the pressure downstream of the turbine wheel 37, is reduced, and the rotational speed of the turbocharger 35 is difficult to increase. The number of rotations of the turbocharger 35 to be reduced is reduced. Therefore, when the atmospheric pressure PA becomes high as described above, the second maximum injection amount QfullJ is increased accordingly, the restriction on the fuel injection amount by the maximum injection amount QfullJ is relaxed, and the air using the turbocharger 35 is increased. It is preferable to improve the engine output as much as possible by supercharging.
[0075]
Contrary to the above, when the atmospheric pressure PA becomes lower, the atmospheric pressure correction coefficient FPA becomes larger due to the change in the atmospheric pressure PA, so the second maximum injection amount QfullJ becomes a smaller value than before. When the atmospheric pressure PA is lowered and the compressor pre-pressure is lowered, the rotational speed of the turbocharger 35 at a certain supercharging pressure PIM regulated by the wastegate valve 52 becomes higher, and the turbine post-pressure is lowered. As a result, the difference in the turbine front-rear pressure becomes large and the rotational speed of the turbocharger 35 is likely to increase. Therefore, the rotational speed of the turbocharger 35 driven by the exhaust increases. Therefore, when the atmospheric pressure PA becomes low as described above, the second maximum injection amount QfullJ is reduced accordingly, and the fuel injection amount is strictly limited by the maximum injection amount QfullJ. Is preferably prevented from becoming larger than the upper limit.
[0076]
Further, the second maximum injection amount QfullJ becomes a smaller value than before because the outside air temperature correction coefficient FAo becomes large due to the change in the outside air temperature THAo when the outside air temperature THAo becomes high. When the outside air temperature THAo increases, the energy of the exhaust gas sent to the exhaust passage 33 increases, and the rotational speed of the turbocharger 35 driven by the exhaust gas increases. Therefore, when the outside air temperature THAo becomes high as described above, the second maximum injection amount QfullJ is decreased accordingly, and the fuel injection amount by the maximum injection amount QfullJ is strictly limited, and the rotation speed of the turbocharger 35 is increased. Is preferably prevented from becoming larger than the upper limit.
[0077]
Contrary to the above, when the outside air temperature THAo becomes low, the outside air temperature correction coefficient FAo becomes small due to the change in the outside air temperature THAo, so the second maximum injection amount QfullJ becomes a larger value than before. When the outside air temperature THAo is lowered, the energy of the exhaust sent to the exhaust passage 33 becomes relatively small, and the rotational speed of the turbocharger 35 driven by the exhaust becomes low. Therefore, when the outside air temperature THAo is lowered as described above, the second maximum injection amount QfullJ is increased accordingly, the restriction on the fuel injection amount by the maximum injection amount QfullJ is relaxed, and the air using the turbocharger 35 is reduced. It is preferable to improve the engine output as much as possible by supercharging.
[0078]
As described above, even if the turbine post-pressure of the turbocharger 35 and the pre-compressor pressure of the turbocharger 35 or the energy of the exhaust gas changes due to changes in the atmospheric pressure PA and the outside air temperature THAo, the atmospheric pressure correction coefficient FPA The second maximum injection amount QfullJ is corrected by the temperature correction coefficient FAo, and the second maximum injection amount QfullJ increases or decreases according to the turbine front-rear pressure, the compressor pre-pressure, and the energy of the exhaust. By restricting the fuel injection amount by the second maximum injection amount QfullJ, it is possible to accurately suppress the rotation speed of the turbocharger 35 from exceeding the upper limit value regardless of changes in the atmospheric pressure PA and the outside air temperature THAo. Will be able to.
[0079]
According to the embodiment described in detail above, the following effects can be obtained.
(1) A first maximum injection amount QfullO is calculated based on parameters affecting the black smoke in the exhaust gas such as the engine speed NE, the supercharging pressure PIM, and the intake air temperature THAi, and the engine speed NE, the atmospheric pressure PA, The second maximum injection amount QfullJ is calculated based on parameters that affect the rotational speed of the turbocharger 35, such as the outside air temperature THAo. Of these first and second maximum injection amounts QfullO and QfullJ and the basic injection amount Qbse for obtaining the output of the diesel engine 11 requested by the driver, the smallest injection is used as the final injection amount Qfin. An amount of fuel corresponding to the amount Qfin was injected into the combustion chamber 16.
[0080]
Therefore, when black smoke is to be suppressed, the first maximum injection amount QfullO becomes smaller than the other injection amounts QfullJ and Qbse, and the first maximum injection amount QfullO becomes the final injection amount Qfin. By performing fuel injection into the combustion chamber 16 based on this final injection amount Qfin, black smoke in the exhaust is accurately suppressed. When the rotational speed of the turbocharger 35 is to be suppressed, the second maximum injection amount QfullJ is smaller than the other injection amounts QfullO and Qbse, and the second maximum injection amount QfullJ becomes the final injection amount Qfin. By performing fuel injection into the combustion chamber 16 based on the final injection amount Qfin, the rotational speed of the turbocharger 35 is suppressed from becoming higher than the upper limit value.
[0081]
In this way, suppression of black smoke and suppression of increase in the rotational speed of the turbocharger 35 are performed separately by limiting the fuel injection amount by the first and second maximum injection amounts QfullO and QfullJ, respectively. Therefore, it is possible to limit the fuel injection amount by the first maximum injection amount QfullO to an amount necessary for suppressing black smoke, and to limit the fuel injection amount by the second maximum injection amount QfullJ of the turbocharger 35. Only the amount necessary for suppressing the increase in the rotational speed can be achieved.
[0082]
Accordingly, when the rotational speed of the turbocharger 35 has a margin with respect to the upper limit value, when the fuel injection amount is limited by the first maximum injection amount QfullO to suppress black smoke, the rotation of the turbocharger 35 is caused by this limitation. The increase in the number is not excessively suppressed. Therefore, the fuel injection amount for suppressing the black smoke by the first maximum injection amount QfullO is suppressed while suppressing the rotation speed of the turbocharger 35 from being excessively high due to the restriction of the fuel injection amount by the second maximum injection amount QfullJ. When this restriction is performed, it is possible to prevent an increase in the rotational speed of the turbocharger 35 from being excessively suppressed and unnecessarily lowering the engine output.
[0083]
(2) The first maximum injection amount QfullO is an intake pressure determined based on the boost pressure correction coefficient FP determined based on the boost pressure PIM and the intake air temperature THAi with respect to the base value QfullB determined based on the engine speed NE. It is calculated by multiplying by the temperature correction coefficient FAi. Since the first maximum injection amount QfullO is calculated using a plurality of parameters affecting black smoke as described above, the first maximum injection amount QfullO is made more appropriate for suppressing the generation of black smoke. be able to.
[0084]
(3) The second maximum injection amount QfullJ is calculated based on the atmospheric pressure correction coefficient FPA obtained on the basis of the atmospheric pressure PA and the outside air temperature correction obtained on the basis of the outside air temperature THAo with respect to the base value QfullF obtained on the basis of the engine speed NE. It is calculated by multiplying the coefficient FAo. Since the second maximum injection amount QfullJ is calculated using a plurality of parameters that affect the rotational speed of the turbocharger 35 in this way, the second maximum injection amount QfullJ is suppressed from increasing in the rotational speed of the turbocharger 35. More appropriate.
[0085]
In addition, this embodiment can also be changed as follows, for example.
In the present embodiment, the first maximum injection amount QfullO is calculated using the engine speed NE, the supercharging pressure PIM, and the intake air temperature THAi as parameters that affect black smoke. There is no need to use it.
[0086]
A parameter other than the engine speed NE, the supercharging pressure PIM, and the intake air temperature THAi may be adopted as a parameter affecting black smoke.
In the present embodiment, the second maximum injection amount QfullJ is calculated using the engine speed NE, the atmospheric pressure PA, and the outside air temperature THAo as parameters that affect the speed of the turbocharger 35. It is not necessary to use all parameters.
[0087]
As parameters affecting the rotational speed of the turbocharger 35, parameters other than the engine rotational speed NE, the atmospheric pressure PA, and the outside air temperature THAo may be adopted.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an entire diesel engine to which a fuel injection control device of an embodiment is applied.
FIG. 2 is a flowchart showing a procedure for calculating a final injection amount Qfin.
FIG. 3 is a map that is referred to when a basic injection amount Qbse is calculated.
FIG. 4 is a flowchart showing a procedure for calculating a first maximum injection amount QfullO.
FIG. 5 is a map referred to when calculating a base value QfullB.
FIG. 6 is a map that is referred to when a supercharging pressure correction coefficient FP is calculated.
FIG. 7 is a map that is referred to when calculating an intake air temperature correction coefficient FAi.
FIG. 8 is a flowchart showing a procedure for calculating a second maximum injection amount QfullJ.
FIG. 9 is a map referred to when calculating a base value QfullF.
FIG. 10 is a map referred to when calculating an atmospheric pressure correction coefficient FPA.
FIG. 11 is a map that is referred to when calculating an outside air temperature correction coefficient FAo.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Diesel engine, 16 ... Combustion chamber, 17 ... Intake temperature sensor, 18 ... Vacuum switching valve (VSV), 19 ... Pressure sensor, 20 ... Injection nozzle, 26 ... Accelerator position sensor, 35 ... Turbocharger, 41 ... Fuel injection Pump, 43 ... electromagnetic spill valve, 45 ... rotational speed sensor, 46 ... atmospheric temperature sensor, 92 ... electronic control unit (ECU).

Claims (5)

A turbocharger that supercharges the air supplied to the combustion chamber of the diesel engine is provided, and the basic injection amount for obtaining the required engine output is calculated based on the engine operating state, and the final injection amount obtained from the basic injection amount is calculated. In a fuel injection control device for a diesel engine that performs fuel injection based on
Based on the engine speed of the diesel engine, the air supercharging pressure by the turbocharger, and the intake air temperature of the diesel engine, a first maximum injection amount that is the maximum fuel injection amount that can allow the black smoke is First maximum injection amount calculating means for calculating;
Second maximum injection amount calculation means for calculating a second maximum injection amount that is a fuel injection amount when the rotation speed of the turbocharger reaches an upper limit value based on the engine speed, the atmospheric pressure, and the outside air temperature; ,
A final injection amount calculating means for setting the smallest injection amount among the basic injection amount, the first maximum injection amount, and the second maximum injection amount as a final injection amount;
The fuel injection control apparatus for a diesel engine comprising: a. The first maximum injection amount calculating means calculates the first maximum injection amount as a smaller value as the supercharging pressure becomes lower.
The fuel injection control device for a diesel engine according to claim 1 . The first maximum injection amount calculation means calculates the first maximum injection amount as a smaller value as the intake air temperature becomes higher.
The fuel injection control device for a diesel engine according to claim 1 or 2 . The second maximum injection amount calculating means calculates the second maximum injection amount as a smaller value as the atmospheric pressure becomes lower.
The fuel-injection control apparatus of the diesel engine in any one of Claims 1-3 . The second maximum injection amount calculating means calculates the second maximum injection amount as a smaller value as the outside air temperature becomes higher.
The fuel-injection control apparatus of the diesel engine in any one of Claims 1-4 .

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