JP5098938B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to an engine fuel injection control device.

  Conventionally, a fuel injection device for the purpose of suppressing misfire of a diesel engine is known. For example, a fuel injection timing control device for a diesel engine that performs fuel injection timing control according to the operating state of the diesel engine is known (see Patent Document 1). This fuel injection timing control device determines the fuel injection timing for suppressing misfire by referring to the operating state of the diesel engine, that is, the engine speed, engine load, intake pressure, cooling water temperature, and intake air temperature. .

JP 2000-186598 A

  By the way, a diesel engine may be equipped with an EGR (Exhaust Gas Recirculation) device. The EGR device has an EGR pipe between the exhaust side and the intake side, and introduces exhaust into the cylinder. One purpose of a diesel engine equipped with an EGR device is to reduce the oxygen concentration in the cylinder and reduce NOx. For this reason, the EGR device controls the opening and closing of an EGR valve provided in the EGR pipe, and adjusts the introduction amount of exhaust gas (EGR gas).

  Such an EGR device inevitably causes a transient delay in the in-cylinder oxygen concentration due to a delay in the EGR gas flow in the pipe, a response delay in the EGR valve, and the like, and this transient delay causes a misfire in the cylinder. It may cause. That is, misfire in the cylinder is affected by the oxygen concentration in the cylinder, so if a transient delay occurs in the cylinder oxygen concentration, this may affect the fuel injection control and cause misfire.

  In addition, in a diesel engine, there is also a problem that smoke is likely to occur if the amount of oxygen in the cylinder is insufficient. The transient delay caused by the EGR device also causes a shortage of oxygen in the cylinder.

  The fuel injection timing control device disclosed in Patent Document 1 is aimed at suppressing misfire as described above. However, the oxygen concentration in the cylinder is not considered in the fuel injection timing control. Further, suppression of smoke generation is not taken into consideration. Thus, the fuel injection timing control device disclosed in Patent Document 1 has room for further improvement.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection device capable of suppressing misfire and smoke from being caused by a transient delay of in-cylinder oxygen concentration due to introduction of EGR gas in a diesel engine equipped with an EGR device. And

  In order to solve this problem, the fuel injection control device of the present invention includes an engine operating state grasping means, an engine target in-cylinder oxygen concentration acquisition means, and an in-cylinder oxygen concentration obtained by the target in-cylinder oxygen concentration acquisition means. EGR control means for approaching the acquired target in-cylinder oxygen concentration, basic injection timing calculation means for calculating basic injection timing based on the operating state of the engine ascertained by the operating state grasping means, and acquisition of in-cylinder oxygen concentration of the engine Means, a misfire injection timing setting means for setting a fuel injection timing for suppressing misfire based on a value of the in-cylinder oxygen concentration acquired by the in-cylinder oxygen concentration acquisition means, and a misfire guard injection corresponding to the misfire injection timing The misfire guard injection amount setting means for setting the amount, the basic fuel injection amount corresponding to the basic injection timing, and the misfire guard injection amount are compared to reduce the injection amount. And the optimum injection quantity selecting means for selecting whichever is the optimum injection amount, a, is characterized by comprising.

  The operating state grasping means can acquire information related to the engine speed and the engine load. The required injection amount can be calculated from the engine load. The target in-cylinder oxygen concentration acquisition unit acquires the value of the target in-cylinder oxygen concentration based on the information related to these operating states. The EGR control means controls the EGR device so that the in-cylinder oxygen concentration approaches the target in-cylinder oxygen concentration. Then, the basic injection timing calculation means calculates the basic injection timing based on the engine operating state grasped by the operation state grasping means. However, the calculated basic injection timing does not take into account the effect of EGR gas introduction by the EGR device. For this reason, if fuel injection is performed at the basic injection timing calculated based only on the operating state of the engine, a mismatch may occur with the actual oxygen concentration in the cylinder in which the transient delay occurs, leading to misfire. There is.

  Therefore, the fuel injection control device disclosed in this specification includes an in-cylinder oxygen concentration acquisition unit of the engine, and reflects the value acquired by the in-cylinder oxygen concentration acquisition unit in the fuel injection control. The in-cylinder oxygen concentration acquisition means acquires the actual oxygen concentration value at that time. The misfire injection timing setting means sets a fuel injection timing for suppressing misfire based on the value of the in-cylinder oxygen concentration acquired by the in-cylinder oxygen concentration acquisition means. Thereby, it is set as the fuel injection which considered the actual in-cylinder oxygen concentration, and misfire can be suppressed.

  The fuel injection control device disclosed in the present specification has an optimal injection amount selection means. The optimum injection amount selection means compares the basic fuel injection amount corresponding to the basic injection timing with the misfire guard injection amount corresponding to the misfire injection timing, and selects the smaller injection amount as the optimal injection amount. Thereby, misfire can be suppressed in a wide range during engine operation.

  Further, since the fuel injection amount is set in correspondence with the injection timing, the occurrence of smoke can be suppressed at the same time. Smoke is affected by the amount of oxygen in the cylinder, and is easily generated when the amount of oxygen in the cylinder is insufficient. For this reason, if it is attempted to suppress misfire by controlling only the injection timing and advancing the injection timing, there is a concern that the generation of smoke may be worsened due to a decrease in the air amount. Therefore, if the fuel injection amount is set in accordance with the injection timing as described above, the occurrence of smoke can be suppressed.

  The fuel injection control device disclosed in the present specification further includes an excess air ratio calculation unit, and calculates a smoke guard injection amount that suppresses the generation of smoke based on the excess air ratio calculated by the excess air ratio calculation stage. A smoke guard injection amount setting means, wherein the optimum injection amount selection means compares the basic fuel injection amount corresponding to the basic fuel injection timing with the smoke guard injection amount, and selects the smaller injection amount as the optimal injection amount; It can be set as the structure selected as. Thereby, generation | occurrence | production of smoke can be suppressed effectively.

  ADVANTAGE OF THE INVENTION According to this invention, the misfire resulting from the transient delay of a diesel engine provided with an EGR apparatus can be suppressed, and smoke generation can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration around an intake system and an exhaust system of an engine 100 in which the fuel injection control device 1 of the present invention is incorporated. The engine 100 is a water-cooled four-cycle diesel engine. A piston 3 is slidably inserted into the cylinder 5 of the engine 100, and a combustion chamber 2 is formed by the upper surface of the piston 3 and the inner wall of the cylinder 5. A fuel injection valve 6 that directly injects fuel into the combustion chamber 2 is provided at the upper portion of the combustion chamber 2.

  The combustion chamber 2 communicates with the intake pipe 22 via the intake port 20. Further, the combustion chamber 2 communicates with an exhaust pipe 32 via an exhaust port 30. The cylinder 5 is provided with an intake valve 23 that opens and closes an opening at a connection point between the combustion chamber 2 and the intake port 20, and an exhaust valve 33 that opens and closes an opening at a connection point between the combustion chamber 2 and the exhaust port 30. It has been.

  The engine 100 is provided with an EGR device 40 that recirculates a part of the exhaust gas to the combustion chamber 2. The EGR device 40 includes an EGR pipe 41 and an EGR valve 42. The EGR pipe 41 is a pipe connecting the exhaust pipe 32 and the intake pipe 22, and a part of the exhaust gas flowing through the exhaust pipe 32 through the EGR pipe 41 flows into the intake pipe 22 and passes through the intake port 20 to the combustion chamber. 2 is inhaled. The EGR valve 42 is a flow rate control valve that can change the amount of EGR gas flowing through the EGR pipe 41 by changing the flow path cross-sectional area of the EGR pipe 41. The amount of EGR gas can be adjusted by adjusting the opening degree of the EGR valve 42.

  The engine 100 includes an ECU (Electronic control unit) 8 that performs various controls of the engine 100. The ECU 8 connects a read-only memory (ROM), a random access memory (RAM), a central processing unit (CPU), an input / output port, a digital analog converter (DA converter), an analog digital converter (AD converter), etc. with a bidirectional bus. It is configured as a microcomputer having a known configuration.

  The ECU 8 is the “operating state grasping means”, “target in-cylinder oxygen concentration obtaining means”, “EGR control means”, “basic injection timing calculating means”, “misfire injection timing setting means”, “misfire guard injection amount” in the present invention. It functions as each means of “setting means”, “optimum injection amount selecting means”, “excess air ratio calculating means”, and “smoke guard injection amount setting means”.

  Then, the ECU 8 performs control such as control of the fuel injection amount and fuel injection timing by the fuel injection valve 6 in accordance with the operation state of the engine 100 and the request from the driver.

  Therefore, the ECU 8 is electrically connected with an engine speed sensor 70 that acquires the engine speed NE and an accelerator opening sensor 71 that detects the amount of depression of the accelerator pedal 7 (accelerator opening) Accp by the driver. Yes. In-cylinder oxygen concentration sensor 72 that corresponds to the in-cylinder oxygen concentration acquisition means in the present invention and that actually detects the in-cylinder oxygen concentration of the engine is also electrically connected to ECU 8. Further, the air flow meter 73 is also electrically connected to the ECU 8.

  In addition, although illustration and description are omitted, sensors that are generally provided in the engine 100 are provided, and these sensors are connected to the ECU 8 through electric wiring, and output signals from the sensors are input to the ECU 8. It has come to be.

  The ECU 8 is connected to devices such as a driving device for driving the fuel injection valve 6 and the EGR valve 42 through electric wiring. The ECU 8 grasps the operating state of the engine 100 and the driver's request based on the detection values by the various sensors, and performs various operations such as the fuel injection valve 6 and the EGR valve 42 according to the operating state of the engine 100 and the driver's request. A control signal is transmitted to the devices to be controlled to control these devices. Various operating parameters (for example, fuel injection amount, fuel injection timing, intake air amount, EGR rate, etc.) for performing such control are adapted in advance so that these engine characteristics satisfy predetermined target values and regulations. Is stored in the ROM of the ECU 8 in the form of a map, an arithmetic expression, or the like.

  Next, a policy of fuel injection control performed by the fuel injection control device 1 and an image of control will be described with reference to the chart shown in FIG.

  FIG. 2 is a chart showing changes in “engine speed”, “requested injection amount”, “in-cylinder oxygen concentration”, “injection timing”, and “command injection amount” with the horizontal axis as the time axis. ing. Note that the “engine speed” is a steady state where the engine speed NE = N1 in order to simplify the explanation.

When the accelerator 7 is depressed at the timing of t1, instantly required injection amount Qr is increased from Qr ₁ to Qr _2. The ECU 8 determines the value of the target in-cylinder oxygen concentration Roxctrg based on the required injection amount Qr ₂ and the engine speed N1. The target in-cylinder oxygen concentration Roxctrg rises from R ₁ to R ₂ in synchronization with the rise of the required injection amount from Qr ₁ to Qr _{2 as} shown by the broken line in FIG. That is, the transition from R ₁ to R ₂ is instantaneously performed at the timing t1, and the waveform rises vertically.

  The ECU 8 adjusts the opening degree of the EGR valve 42 so as to achieve such a target in-cylinder oxygen concentration Roxctrg, and introduces EGR gas into the combustion chamber 2. However, there is a time lag after the ECU 8 issues a command to the EGR valve 42 until the EGR valve 42 actually reaches the desired opening. Further, there is a delay in the gas flow until the EGR gas passing through the EGR pipe 41 reaches the combustion chamber 2. For this reason, the actual in-cylinder oxygen concentration gradually approaches the target oxygen concentration as shown by a solid line in FIG. That is, a transient delay occurs.

  The ECU 8 calculates the target in-cylinder oxygen concentration based on the operating state of the engine as described above, and further calculates the basic injection timing ainjmbse from the target in-cylinder oxygen concentration Roxctrg. The basic injection timing ainjmbse calculated in this way is indicated by a broken line in FIG. The ECU 8 also calculates the injection timing based on the actual in-cylinder oxygen concentration Roxc. The injection timing calculated based on the actual in-cylinder oxygen concentration is the misfire injection timing ainjmax. The misfire injection timing ainjmax is set as an injection timing that may cause misfire if it is injected at a retarded angle from this timing. The misfire injection timing ainjmax is indicated by a solid line in FIG. As is apparent from FIG. 2, the basic injection timing ainjmbse is later than the misfire injection timing ainjmax at the timing from time t1 to t2, that is, on the retard side. In this way, when the basic injection timing ainjmbse is later than the misfire injection timing ainjmax, it can be determined that misfire occurs when fuel is injected at the basic injection timing ainjmbse. Therefore, when the basic injection timing ainjmbse is later than the misfire injection timing ainjmax, the injection is performed at the misfire injection timing ainjmax instead of the basic injection timing ainjmbse. Thereby, misfire can be suppressed.

Further, the ECU 8 sets the fuel injection amount according to the set injection timing. When injection is performed at the basic injection timing ainjmbse, the basic fuel injection amount corresponding to the basic injection timing ainjmax is employed as the optimal injection amount. Here, the basic fuel injection amount is the required injection amount obtained previously, and Qr shown in FIG. 2, that is, Qr ₁ or Qr ₂ is adopted as the optimum injection amount. On the other hand, at the timing when the misfire injection timing ainjmax is selected, the misfire guard injection amount Qx is selected as the optimum injection amount. That is, Qr and Qx are compared and the smaller one is adopted as the optimum injection amount. Thereby, it is possible to avoid the occurrence of smoke by avoiding a state where the oxygen amount is insufficient, in other words, an excessive amount of fuel.

  An example of fuel injection control performed under the above control policy will be described with reference to the flowchart shown in FIG.

  In step S1, the ECU 8 obtains the engine speed NE from the engine speed sensor 70. Further, Accp is detected from the accelerator opening sensor 71, and the required injection amount Qr is acquired from the detected value.

In step S2 performed subsequent to step S1, the target in-cylinder oxygen concentration Roxctrg is calculated. FIG. 4 shows an example of a map for calculating the target in-cylinder oxygen concentration Roxctrg. The map shown in FIG. 4 has the engine speed NE and the required injection amount Qr as parameters, and the target in-cylinder oxygen concentration Roxctrg is derived for each combination. In FIG. 4, the target in-cylinder oxygen concentration Roxctrg indicates that the concentration is higher as the value of N of the level “N” is larger. FIG. 5 is a diagram showing a part of the map shown in FIG. 4 and showing the relationship between the required injection amount Qr and the target in-cylinder oxygen concentration Roxctrg when the engine speed NE = N1 (rpm). It is. The required injection amount Qr (mm ³ / st) is taken on the horizontal axis in FIG. 5, and the target in-cylinder oxygen concentration Roxctrg (% (wt)) is taken on the vertical axis. Here, if the required injection amount Qr of the operating condition desired to be realized from the torque request of the engine 100 is N1 (rpm) and Qa (mm ³ / st), the target in-cylinder oxygen concentration Roxctrg is Ra (% (wt )).

  In step S3 performed subsequent to step S2, the ECU 8 issues a drive command to the EGR valve 42 to perform EGR control so that the target in-cylinder oxygen concentration Roxctrg obtained in step S2 is obtained.

After the process of step S3 is completed, the actual in-cylinder oxygen concentration Roxc at the present time is acquired in step S4. The actual in-cylinder oxygen concentration Roxc (% (wt)) is directly measured and acquired by the in-cylinder oxygen concentration sensor 72.
Here, it is assumed that the actual in-cylinder oxygen concentration Roxc (% (wt)) is Rb (% (wt)) smaller than the target in-cylinder oxygen concentration Ra (% (wt)). In this case, the actual in-cylinder oxygen concentration is deficient in the target in-cylinder oxygen concentration by (Ra−Rb) (% (wt)).
The in-cylinder oxygen concentration Roxc can be a value calculated using various parameters. In this embodiment, the in-cylinder oxygen concentration sensor 72 is provided. For example, an in-cylinder oxygen concentration sensor 72 is attached to the intake manifold, and the in-cylinder oxygen concentration Roxc is obtained using a value acquired by the oxygen concentration sensor. May be calculated.

  After acquiring the actual in-cylinder oxygen concentration Roxc in step S4, the process proceeds to step S5. In step S5, the basic injection timing ainjmbse obtained from the engine speed NE and the required injection amount Qr is set. FIG. 6 shows an example of a map for calculating the basic injection timing ainjmbse. The map shown in FIG. 6 has the engine speed NE and the required injection amount Qr as parameters, and the basic injection timing ainjmbse is derived for each combination. In FIG. 6, the basic injection timing ainjmbase indicates that the larger the value of N of the level “N” is, the more the advanced injection side is set. FIG. 7 is a diagram showing a part of the map shown in FIG. 6 and showing the relationship between the required injection amount Qr and the basic injection timing ainjmbse when the engine speed NE = N1 (rpm). . The required injection amount Qr is taken on the horizontal axis of FIG. 7, and the basic injection timing ainjmbse is taken on the vertical axis. Here, if the engine speed NE of the operating condition desired to be realized from the torque request of the engine 100 is N1 and the required injection amount Qr is Qa, the basic injection timing ainjmbse is θa.

In step S6 performed subsequent to step S5, the ECU 8 sets the misfire injection timing ainjmax. FIG. 8 shows an example of a map for calculating the misfire injection timing ainjmax. The misfire injection timing ainjmax is calculated based on the in-cylinder oxygen concentration. In this embodiment, the misfire injection timing ainjmax is calculated based on the actual in-cylinder oxygen concentration Roxc = Rb acquired in step S4, and θb is obtained. This θb is a value on the more advanced side than θa calculated as the basic injection timing ainjmbse. As described above, when the misfire injection timing ainjmax is advanced from the basic injection timing ainjmbse, the misfire injection timing ainjmax is set as the injection timing.
Thus, misfire can be suppressed by comparing the basic injection timing ainjmbse with the misfire injection timing ainjmax and selecting the more advanced injection timing.

  In the process of step S7 performed subsequent to step S6, the misfire guard injection amount Qx corresponding to the misfire injection timing ainjmax is set. The misfire guard injection amount Qx is calculated using the map shown in FIG. The vertical axis of the map shown in FIG. 7 is the basic injection timing ainjmbse as described above. The value of the misfire injection timing ainjmax is applied to this vertical axis, and the value of the required injection amount obtained therefrom is calculated. Misfire guard injection amount. As shown in FIG. 7, in this embodiment, when θb is set as the misfire injection timing ainjmax, Qx corresponding to θb is set as the misfire guard injection amount.

The ECU 8 calculates the optimum injection amount Q in step S8 performed subsequent to step 7. The optimal injection quantity Q is
Q = MIN (Qr, Qx).
That is, the required injection amount Qr obtained in step S1 is compared with the misfire guard injection amount Qx obtained in step S7, and the smaller one is set as the optimum injection amount Q. As described above, by setting the smaller one of the basic injection amount corresponding to the basic injection timing and the misfire guard injection amount corresponding to the misfire injection timing as the optimum injection amount Q, the occurrence of smoke due to oxygen shortage Can be suppressed.

  Next, a second embodiment of the present invention will be described. Since the configuration of the engine 100 is the same as that of the first embodiment, detailed description thereof is omitted. Example 2 differs from Example 1 in that Example 1 focuses on the in-cylinder oxygen concentration and performs fuel injection control, whereas Example 2 focuses on the amount of air in the cylinder. Thus, fuel injection control is performed. The second embodiment is intended to more appropriately suppress the generation of smoke by appropriately controlling the amount of air in the cylinder. The control policy is as follows.

The ECU 8 corresponds to the excess air ratio calculating means in the present invention. The ECU 8 calculates an excess air ratio, and calculates a smoke guard injection amount Qy that suppresses the generation of smoke based on the excess air ratio. The calculation of the smoke guard injection amount is performed by the ECU 8 corresponding to the smoke guard injection amount setting means.
Then, the ECU 8 corresponding to the optimum injection amount selection means compares the basic fuel injection amount corresponding to the basic fuel injection timing ainjmbse, that is, the required injection amount Qr with the smoke guard injection amount Qy, and selects the one with the smaller injection amount. The optimum injection amount Q is selected.
By performing such fuel injection control, the generation of smoke can be suppressed.

  An example of the fuel injection control performed according to the above policy will be described with reference to the flowchart shown in FIG.

  In step S11, the ECU 8 acquires the engine speed NE from the engine speed sensor 70. Further, Accp is detected from the accelerator opening sensor 71, and the required injection amount Qr is acquired from the detected value. This process is the same process as step S1 of the first embodiment.

In step S12 performed subsequent to step S11, the target in-cylinder oxygen concentration Roxctrg is calculated. This process corresponds to the process of step S2 in the first embodiment, and the target in-cylinder oxygen concentration Roxctrg is calculated by referring to the map shown in FIG. Assuming that the required injection amount Qr of the operating condition to be realized from the torque request of the engine 100 is N1 (rpm) and Qa (mm ³ / st), the target in-cylinder oxygen concentration Roxctrg is the same as in the first embodiment. Ra (% (wt)).

  In step S13 performed subsequent to step S12, the ECU 8 issues a drive command to the EGR valve 42 so as to perform EGR control so that the target in-cylinder oxygen concentration Roxctrg obtained in step S12 is obtained. This process is also common to the process of step S3 in the first embodiment.

After the process of step S13 is completed, the actual in-cylinder oxygen concentration Roxc at the present time is acquired in step S14. The actual in-cylinder oxygen concentration Roxc (% (wt)) is directly measured and acquired by the in-cylinder oxygen concentration sensor 72.
Here, it is assumed that the actual in-cylinder oxygen concentration Roxc (% (wt)) is Rb (% (wt)) smaller than the target in-cylinder oxygen concentration Ra (% (wt)). In this case, the actual in-cylinder oxygen concentration is deficient in the target in-cylinder oxygen concentration by (Ra−Rb) (% (wt)).

  Such processing in step S14 is common to the processing in the first embodiment. However, in the second embodiment, the intake air amount gn is acquired together with the acquisition of the in-cylinder oxygen concentration Roxc. The intake air amount gn is grasped from the measured value of the air flow meter 73.

  After acquiring the actual in-cylinder oxygen concentration Roxc and the intake air amount gn in step S14, the process proceeds to step S15. In step S15, a basic injection timing ainjmbse obtained from the engine speed NE and the required injection amount Qr is set. This process corresponds to the process of step S5 in the first embodiment, and the basic injection timing ainjmbse is calculated by referring to the map shown in FIG. If the engine speed NE is N1 and the required injection amount Qr is Qa under the operating conditions desired to be realized from the torque request of the engine 100, the basic injection timing ainjmbse is θa.

In step S16 performed subsequent to step S15, the ECU 8 sets the misfire injection timing ainjmax. This process is the same as step S6 in the first embodiment, and the misfire injection timing ainjmax is calculated by referring to the map shown in FIG. In the present embodiment, as in the case of the first embodiment, the misfire injection timing ainjmax is calculated based on the actual in-cylinder oxygen concentration Rb acquired in step S14, and θb is obtained. This θb is a value on the more advanced side than θa calculated as the basic injection timing ainjmbse. As described above, when the misfire injection timing ainjmax is advanced from the basic injection timing ainjmbse, the misfire injection timing ainjmax is set as the injection timing.
Thus, misfire can be suppressed by comparing the basic injection timing ainjmbse with the misfire injection timing ainjmax and selecting the more advanced injection timing.

ここで、ρｆ［ｇ／ｃｍ^３］は燃料密度である。
また、空気過剰率のスモーク限界λｍｉｎは、図１０に示すマップを参照することによって決定される。図１０に示すマップは、スモーク限界λｍｉｎを決定するためのマップの一例を示すものであるが、パラメータとしてエンジン回転ＮＥ（ｒｐｍ）、要求噴射量Ｑｒ（ｍｍ^３／ｓｔ）を有している。スモーク限界λｍｉｎは、エンジン回転数が小さく、要求噴射量が小さいほど値が大きくなり、エンジン回転数が大きく、要求噴射量が大きいほど値が小さくなる。
このようにして算出された値がスモークガード噴射量Ｑｙとして設定される。 In the process of step S17 performed subsequent to step S16, the smoke guard injection amount Qy is calculated from the smoke limit λmin of the excess air ratio. The smoke guard injection amount Qy is obtained by the following equation 1.
Formula 1

Here, ρf [g / cm ³ ] is the fuel density.
Also, the smoke limit λmin of the excess air ratio is determined by referring to the map shown in FIG. The map shown in FIG. 10 shows an example of a map for determining the smoke limit λmin, and has the engine rotation NE (rpm) and the required injection amount Qr (mm ³ / st) as parameters. The smoke limit λmin increases as the engine speed decreases and the required injection amount decreases, and decreases as the engine speed increases and the required injection amount increases.
The value calculated in this way is set as the smoke guard injection amount Qy.

The ECU 8 calculates the optimum injection amount Q in step S18 performed subsequent to step 17. The optimal injection quantity Q is
Q = MIN (Qr, Qy).
That is, the required injection amount Qr obtained in step S11 is compared with the smoke guard injection amount Qy obtained in step S17, and the smaller value is set as the optimum injection amount Q. Thus, by setting the smaller one of the basic injection amount corresponding to the basic injection timing and the smoke guard injection amount as the optimum injection amount Q, the generation of smoke due to oxygen shortage is effectively suppressed. be able to.

  As in the first embodiment, the misfire guard injection amount Qx may be calculated, and the optimum injection amount R may be selected from the misfire guard injection amount Qx, the smoke guard injection amount Qy, and the required injection amount Qr.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

FIG. 1 is an explanatory diagram showing a schematic configuration around an intake system and an exhaust system of an engine in which a fuel injection control device of an embodiment is incorporated. FIG. 2 is a chart showing an image of control of the fuel injection control device. FIG. 3 is a flowchart showing an example of control by the fuel injection control device. FIG. 4 is an example of a map for acquiring the target in-cylinder oxygen concentration. FIG. 5 is a chart showing the relationship between the required injection amount and the target in-cylinder oxygen concentration when the engine speed is N1 in the map shown in FIG. FIG. 6 is an example of a map for acquiring the basic injection timing. FIG. 7 is a chart showing the relationship between the required injection amount and the basic injection timing when the engine speed is N1 in the map shown in FIG. FIG. 8 is an example of a map for calculating the misfire injection timing from the in-cylinder oxygen concentration. FIG. 9 is a flowchart illustrating an example of control performed by the fuel injection control apparatus according to the second embodiment. FIG. 10 is an example of a map for calculating the smoke limit λmin from the engine speed NE and the required injection amount Qr.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel injection control apparatus 2 ... Combustion chamber 3 ... Piston 5 ... Cylinder 7 ... Accelerator pedal 8 ... ECU
DESCRIPTION OF SYMBOLS 20 ... Intake port 22 ... Intake pipe 23 ... Intake valve 30 ... Exhaust port 32 ... Exhaust pipe 33 ... Exhaust valve 40 ... EGR apparatus 41 ... EGR pipe 42 ... EGR valve 70 ... Engine speed sensor 71 ... Accelerator opening degree sensor 72 ... In-cylinder oxygen concentration sensor 73 ... Air flow meter

Claims (2)

Engine operating state grasping means,
Engine in-cylinder oxygen concentration acquisition means;
EGR control means for bringing the in-cylinder oxygen concentration close to the target in-cylinder oxygen concentration acquired by the target in-cylinder oxygen concentration acquisition means;
Basic injection timing calculating means for calculating basic injection timing based on the operating state of the engine ascertained by the operating condition grasping means;
In-cylinder oxygen concentration acquisition means of the engine;
Misfire injection timing setting means for setting a fuel injection timing for suppressing misfire based on the value of the in-cylinder oxygen concentration acquired by the in-cylinder oxygen concentration acquisition means;
Misfire guard injection amount setting means for setting a misfire guard injection amount corresponding to the misfire injection timing;
The basic injection timing calculated by the basic injection timing calculation means and the misfire injection timing set by the misfire injection timing setting means are compared to select the advance side injection timing, and to the selected injection timing An optimal injection amount selecting means for selecting the corresponding fuel injection amount as the optimal injection amount;
A fuel injection control device comprising: An excess air ratio calculating means,
Smoke guard injection amount setting means for calculating a smoke guard injection amount that suppresses the generation of smoke based on the excess air ratio calculated by the excess air ratio calculation stage,
The optimum injection amount selection means has an advanced injection timing selected by comparing the basic injection timing calculated by the basic injection timing calculation means with the misfire injection timing set by the misfire injection timing setting means. 2. The fuel injection control device according to claim 1 , wherein a fuel injection amount corresponding to the fuel injection amount and the smoke guard injection amount are compared, and the smaller injection amount is selected as the optimum injection amount.

Images