JP2019167834A - Fuel injection control device fuel injection control method - Google Patents

Abstract

To inject fuel at proper timing irrespective of a secular change of a fuel injection device, and to suppress a generation amount of soot which is generated by the combustion of the fuel.SOLUTION: A fuel injection control device for controlling a fuel injection device of a diesel engine having a cylinder and a piston reciprocating in the cylinder, and formed with a recess constituting a part of a combustion chamber at an apex of the piston comprises: an acquisition part 21 for acquiring an actual fuel injection period of the fuel injection device; a first comparison part 22 for comparing the fuel injection period acquired by the acquisition part 21 and a prescribed threshold; a first decision part 23 for deciding an injection period of fuel which is injected into the combustion chamber so as to suppress a generation amount of soot which is generated by the combustion of the fuel on the basis of a comparison result of the first comparison part 22; and a fuel injection control part 27 for controlling the fuel injection device so as to inject the fuel on the basis of the injection period which is decided by the first decision part 23.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel injection control device and a fuel injection control method.

  A concave cavity is formed at the top of the piston that reciprocates the cylinder of the diesel engine, and a combustion chamber is formed in a space surrounded by the top of the piston having the cavity and the inner surface of the cylinder. Depending on the shape of the cavity, the amount of soot generated during fuel combustion increases or decreases.

  Patent Documents 1 and 2 listed below disclose techniques for increasing the degree of mixing of fuel and air by changing the shape of the cavity of the combustion chamber and reducing soot produced by fuel combustion.

  In addition, the amount of soot generated can be suppressed by adjusting the timing of injecting fuel into the combustion chamber formed in the cylinder. The fuel injection timing is finely set according to the engine operating conditions (for example, the engine speed and the fuel injection amount), and the fuel injection timing is controlled according to the actual operating conditions. The fuel injection timing is set to minimize the amount of soot generated, for example, by preventing the fuel from being biased either inside the cavity or outside the cavity to form a local fuel-rich region. Has been.

Japanese Patent No. 5338268 (Japanese Patent Laid-Open No. 2010-121383) JP 2013-53572 A

  The amount of soot is related to the position at which the injected fuel reaches the cavity (fuel arrival position). At the beginning of production and sales, the fuel arrival position is set so that the amount of soot generated is minimized. The setting of the fuel arrival position is important because the amount of soot generated varies greatly when the fuel arrival position changes slightly.

  On the other hand, when the injector 9 is deteriorated due to a reduction in the cross-sectional area of the flow path caused by impurities mixed in the fuel, the fuel injection amount per unit time is reduced. On the other hand, since the fuel injection amount per time is maintained, the fuel injection period is prolonged. As a result, even if the fuel injection timing is controlled in accordance with the actual operating conditions, the fuel arrival position may change from the initial stage of manufacture and sale due to deterioration with time, and the soot generation amount may gradually increase. This is because the fuel distribution ratio inside and outside the cavity changes.

  Although it is conceivable to replace the fuel injection device such as the injector 9 with respect to the increase in the soot generation amount, it is difficult to replace the fuel injection device in consideration of cost and labor.

  The generated soot can be removed by a DPF (diesel particulate filter) installed on the downstream side, but fuel is used for the regeneration process of the DPF. Therefore, in order to reduce the frequency of the DPF regeneration process, that is, the fuel consumption, it is desirable to reduce the soot generation amount and reduce the dependency on the DPF as much as possible.

  The present invention has been made in view of such circumstances, so that fuel can be injected at an appropriate timing regardless of a change in the fuel injection device over time, and soot generated by the combustion of the fuel. It is an object of the present invention to provide a fuel injection control device and a fuel injection control method capable of suppressing the generation amount.

In order to solve the above problems, the fuel injection control device and the fuel injection control method of the present invention employ the following means.
That is, a fuel injection control device according to the present invention includes an engine fuel injection device that includes a cylinder and a piston that reciprocates within the cylinder, and a top portion of the piston is formed with a recess that forms part of a combustion chamber. A fuel injection control device that controls, an acquisition unit that acquires an actual fuel injection period in the fuel injection device, and a first comparison that compares the actual fuel injection period acquired by the acquisition unit with a predetermined threshold value And a first determination unit that determines an injection period of the fuel to be injected into the combustion chamber so as to suppress a generation amount of soot generated by fuel combustion based on a comparison result in the first comparison unit An injection control unit that controls the fuel injection device to inject the fuel based on the injection period determined by the first determination unit.

  According to this configuration, the actual fuel injection period in the fuel injection device is acquired, compared with a predetermined threshold value, and based on the comparison result, the amount of soot generated due to fuel combustion is suppressed. The fuel injection period is determined. Then, the fuel injection device is controlled to inject fuel based on the determined injection period. As a result, since the fuel is injected during the fuel injection period, even if the fuel injection period deviates from the initial period due to deterioration over time, the fuel can be injected at an appropriate timing, and soot generated by the combustion of the fuel. Can be suppressed.

  In the above invention, based on a load detection unit that detects an engine load, a second comparison unit that compares the engine load detected by the load detection unit with a predetermined first threshold value, and a comparison result in the second comparison unit. And a first determination unit that determines whether or not correction for increasing the actual fuel injection pressure can be performed in relation to a predetermined maximum fuel injection pressure, wherein the actual fuel is determined in the first determination unit. When it is determined that the injection pressure cannot be increased, the injection control unit maintains the actual fuel injection pressure and injects the fuel based on the injection period determined by the first determination unit. When the fuel injection device is controlled and the first determination unit determines that the actual fuel injection pressure can be increased, the injection control unit increases the actual fuel injection pressure, and the actual fuel injection pressure is increased. It may be allowed to shorten the fuel injection period.

  According to this configuration, the detected engine load is compared with the predetermined first threshold value, and correction for increasing the actual fuel injection pressure in relation to the predetermined maximum fuel injection pressure is performed based on the comparison result. It is determined whether or not it can be performed. When the first determination unit determines that the actual fuel injection pressure cannot be increased, the injection control unit controls the fuel injection device to inject fuel based on the injection period determined by the first determination unit. To do. On the other hand, when it is determined by the first determination unit that the actual fuel injection pressure can be increased, the injection control unit increases the actual fuel injection pressure and shortens the actual fuel injection period.

  In the above invention, the second comparison unit compares the engine load detected by the load detection unit with a predetermined second threshold value, and the first determination unit is based on a comparison result in the second comparison unit. Determining whether the correction of the actual fuel injection period or the actual fuel injection pressure is necessary, and determining that the correction of the actual fuel injection period or the actual fuel injection pressure is unnecessary in the first determination unit. If so, the actual fuel injection period or the actual fuel injection pressure may be maintained.

  According to this configuration, the detected engine load is compared with the second threshold value, and whether or not the actual fuel injection period or the actual fuel injection pressure needs to be corrected is determined based on the comparison result. For example, under low-load (or no-load) operating conditions, the excess air ratio is high and the fuel injection amount is low. Soot is generated even if the fuel injection period is changed and the fuel arrival position is changed. There is almost no effect on the amount. Therefore, the actual fuel injection period or the actual fuel injection pressure is not corrected, and the actual fuel injection period or the actual fuel injection pressure is maintained.

  In the above invention, an exhaust gas recirculation unit that mixes exhaust gas discharged from the engine with combustion air, a second determination unit that determines whether or not exhaust gas recirculation by the exhaust gas recirculation unit is possible, The second determination unit may include a second determination unit that determines the amount of exhaust gas to be recirculated when it is determined that the exhaust gas recirculation unit can recirculate the exhaust gas.

  According to this configuration, the exhaust gas recirculation unit that mixes the exhaust gas discharged from the engine with the combustion air is provided, and it is determined whether or not the exhaust gas recirculation unit can recirculate the exhaust gas. And when it is judged in the 2nd judgment part that the recirculation of the exhaust gas by the exhaust gas recirculation part is possible, the amount of exhaust gas to recirculate is determined. Thereby, even when the exhaust gas is recirculated appropriately and the fuel injection period is changed, an increase in the NOx emission amount can be suppressed.

  A fuel injection control method according to the present invention controls a fuel injection device of a diesel engine having a cylinder and a piston that reciprocates in the cylinder, and a recess that forms a part of a combustion chamber is formed at the top of the piston. A fuel injection control method, wherein the acquisition unit acquires an actual fuel injection period in the fuel injection device; and the first comparison unit sets the fuel injection period acquired by the acquisition unit and a predetermined threshold value. The step of comparing and the injection period of the fuel injected into the combustion chamber so that the first determination unit suppresses the amount of soot generated by the combustion of the fuel based on the comparison result in the first comparison unit And a step of controlling the fuel injection device so that the injection control unit injects the fuel based on the injection period determined by the first determination unit. Tsu and a flop.

  According to the present invention, fuel can be injected at an appropriate timing regardless of changes in the fuel injection device over time, and the amount of soot generated by fuel combustion can be suppressed.

It is a lineblock diagram showing an exhaust gas recirculation system concerning one embodiment of the present invention. It is the schematic which shows the cylinder of the exhaust gas recirculation system which concerns on one Embodiment of this invention. It is a block diagram which shows the control part of the exhaust gas recirculation system which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the exhaust gas recirculation system which concerns on one Embodiment of this invention. It is a graph which shows the relationship between fuel injection (drive current) and a crank angle. It is a graph which shows the relationship between soot discharge amount and NOx discharge amount.

Embodiments according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, an exhaust gas recirculation system 1 according to an embodiment of the present invention includes, for example, a diesel engine (hereinafter referred to as “engine”) 2 having four cylinders, a compressor 3A, a turbine 3B, and a rotary shaft 3C. A supercharger 3 having an intake passage, an intake passage 5, an exhaust passage 6, a recirculation passage 7, and the like are provided.

  The engine 2 includes a cylinder 8 and an injector (fuel injection valve) 9. The piston 11 reciprocates inside the cylinder 8 as shown in FIG. A combustion chamber 10 is formed between the upper surface of the piston 11 and the inner surface of the cylinder 8. A concave cavity 12 is formed on the upper surface (top) of the piston 11. The shape of the cavity 12 increases the degree of mixing of fuel and air and reduces soot caused by fuel combustion. The injector 9 constitutes a fuel injection device together with a fuel injection pump and the like.

  Fuel is injected into the combustion chamber 10 of the engine 2 by the injector 9, and the fuel is combusted in the combustion chamber 10, whereby a predetermined engine output is obtained.

  An intake passage 5 is connected to the combustion chamber 10 and an intake valve for opening and closing the intake port is provided. Further, an exhaust passage 6 is connected to the combustion chamber 10 and an exhaust valve for opening and closing the exhaust port is provided. The amount of intake (air) is adjusted by a throttle valve provided in the intake flow path 5, and the adjusted intake air is pumped by the compressor 3 </ b> A and supplied into each cylinder 8 via the intercooler 13 and the intake valve.

  When the injector 9 is opened and closed by the control unit 20, the fuel injection amount, fuel injection pressure, and fuel injection period injected into the combustion chamber 10 in the cylinder 8 are controlled.

  When the fuel burns in the combustion chamber 10, combustion gas is generated, and the combustion gas becomes exhaust gas and is led from the exhaust valve to the exhaust passage 6. Further, the exhaust gas passes through the turbine 3B, passes through the DPF and the NOx storage catalyst provided in the exhaust passage 6, and is released to the atmosphere. The compressor 3A and the turbine 3B are connected via a rotating shaft 3C.

  In the middle of the exhaust passage 6, a recirculation passage 7 for recirculating a part of the exhaust gas flowing through the exhaust passage 6 to the intake passage 5 is connected. The recirculation flow path 7 mixes the exhaust gas discharged from the engine 2 with the combustion air flowing through the intake flow path 5. The recirculation flow path 7 is provided with an EGR cooler 14 for cooling the recirculated exhaust gas (EGR gas) and an EGR valve 15 for controlling the EGR gas flow rate.

  As shown in FIG. 3, the control unit 20 includes an acquisition unit 21, a first comparison unit 22, a first determination unit 23, a load detection unit 24, a second comparison unit 25, and a first determination unit 26. The injection control unit 27, the second determination unit 28, the second determination unit 29, the recirculation control unit 30, the memory 40, and the like. The operation of the control unit 20 is realized by a hardware resource such as a CPU by executing a pre-recorded program.

  The acquisition unit 21 acquires an actual injector drive current period and a reference current period. The injector drive current is a current that flows when the injector 9 is driven to be opened, and the injector drive current period is a period during which the injector drive current actually flows during operation. That is, the injector drive current period coincides with or approximates the actual fuel injection period during which fuel is actually injected.

  The reference current period is determined in advance and recorded in the memory (storage unit) 40. The reference current period is an optimum injector driving current period determined at the beginning of design and manufacture. The reference current period coincides with or approximates the reference fuel injection period determined at the beginning of design and manufacture. The reference fuel injection period is determined in consideration of the amount of soot generated by fuel combustion. The reference current period is an example of a predetermined threshold value.

  The first comparison unit 22 compares the acquired injector drive current period with the acquired reference current period.

  The first determination unit 23 determines the injection period of the injected fuel based on the comparison result in the first comparison unit 22. When the injector drive current period is equal to or shorter than the reference current period in the comparison result in the first comparison unit 22, the first determination unit 23 determines the fuel injection period in the normal fuel injection control as the actual fuel injection period. When the injector drive current period exceeds the reference current period in the comparison result in the first comparison unit 22, the first determination unit 23 controls the fuel injection period so as to suppress the amount of soot generated by the combustion of the fuel. Alternatively, the correction amount of the fuel injection pressure is calculated. Moreover, the 1st determination part 23 correct | amends a fuel-injection period or fuel-injection pressure, and determines as an actual fuel-injection period or fuel-injection pressure.

  The load detection unit 24 detects an engine load in the engine 2. The engine load may be detected by using an air amount sensor (such as an air flow meter) and the acquired excess air value.

  The second comparison unit 25 compares the engine load detected by the load detection unit 24 with a threshold value (first threshold value or second threshold value).

  Whether or not the first determination unit 26 can perform correction to increase the fuel injection pressure in relation to a predetermined maximum fuel injection pressure, based on the comparison result in the second comparison unit 25 using the first threshold. Judging. The first determination unit 26 determines whether or not it is necessary to correct the actual fuel injection period or the actual fuel injection pressure, based on the comparison result in the second comparison unit 25 using the second threshold value.

  The injection control unit 27 controls the fuel injection device to inject fuel based on the fuel injection period or the fuel injection pressure determined by the first determination unit 23.

  For example, when the first determination unit 26 determines that adjustment to increase the fuel injection pressure cannot be performed, the injection control unit 27 maintains the fuel injection pressure and the fuel injection corrected by the first determination unit 23 The fuel injection device is controlled to inject fuel based on the period. On the other hand, when it is determined by the first determination unit 26 that the fuel injection pressure can be increased, the injection control unit 27 does not change the actual fuel injection start timing, and the fuel injection pressure determined by the first determination unit 23 is set. Based on this, the actual fuel injection pressure is increased. As the actual fuel injection pressure increases, the actual fuel injection period is shortened.

The second determination unit 28 determines whether or not the exhaust gas can be recirculated through the recirculation flow path 7 based on the relationship between the exhaust pressure and the supply air pressure in the engine 2.
When the second determination unit 28 determines that the exhaust gas can be recirculated through the recirculation flow path 7, the second determination unit 29 determines the amount of exhaust gas to be recirculated.
The recirculation control unit 30 adjusts the opening degree of the EGR valve 15 based on the recirculation exhaust gas amount determined by the second determination unit 29.

Next, the operation of the exhaust gas recirculation system 1 according to this embodiment will be described with reference to FIG.
In the control unit 20, first, an injector driving current period is acquired (step S1). Since the injector drive current period coincides with or approximates the actual fuel injection period in which the fuel is actually injected, the actual fuel injection period in the fuel injection device is acquired by acquiring the injector drive current period. Is done.

  Further, in order to determine the length of the actual fuel injection period, a reference current period that is predetermined and recorded in the memory 40 is acquired (step S1). Since the reference current period matches or approximates the reference fuel injection period determined at the beginning of design and manufacture, the reference fuel injection period in the fuel injection device is acquired by acquiring the reference current period.

  Next, the acquired injector drive current period is compared with the acquired reference current period (step S2). When the injector drive current period is equal to or shorter than the reference current period, it is considered that the initially determined injector drive current period has not been prolonged due to deterioration or the like, and therefore normal fuel injection control is performed (step S9).

  On the other hand, when the injector drive current period exceeds the reference current period, the injector drive current period initially determined may be prolonged due to deterioration or the like. In this case, appropriate fuel injection control is performed according to the load of the engine 2.

  In a low load (or no load) operating condition where the load of the engine 2 is a predetermined load (for example, 50%) or less, the fuel injection amount is low, and the required fuel injection amount is set in the combustion chamber 10 of the engine 2. In contrast, there is sufficient (excess) air. That is, under low load (or no load) operating conditions, the excess air ratio is high and the fuel injection amount is low. Under such conditions, even if the fuel arrival position to the cavity 12, that is, the fuel injection rate inside and outside the cavity 12 changes as a result of the change of the fuel injection period, the amount of soot generated is hardly affected. Therefore, normal fuel injection control may be performed without performing fuel injection control according to the present embodiment. That is, the actual fuel injection period or the actual fuel injection pressure is not corrected, and the actual fuel injection period or the actual fuel injection pressure is maintained.

  Therefore, it is determined whether or not the load of the engine 2 exceeds a predetermined load (for example, 50%) (step S3). This determination is made based on the detection result by the load detection unit 24 that detects the load of the engine 2. Alternatively, an air amount sensor (such as an air flow meter) may be used to determine whether or not the load of the engine 2 exceeds a predetermined load (for example, 50%) based on the acquired excess air ratio value.

  When the load of the engine 2 is equal to or less than a predetermined load (for example, 50%), normal fuel injection control is performed because there is almost no effect on the amount of soot generated (step S9).

  On the other hand, when the load of the engine 2 exceeds a predetermined load (for example, 50%), that is, when the load of the engine 2 is a medium load or a high load, appropriate fuel injection control is performed according to the load of the engine 2. I do.

  Next, a difference between the acquired injector drive current period and the acquired reference drive current period is calculated, and a correction amount for changing the fuel injection period is calculated based on the calculated difference (step S4). . The fuel injection period may be changed by (1) increasing the fuel injection pressure to shorten the fuel injection period, and changing the end timing so that fuel is injected during a predetermined reference fuel injection period. (2) The fuel injection start timing and the fuel injection end timing may be changed by maintaining the fuel ratio inside and outside the combustion chamber cavity without maintaining the fuel injection pressure to shorten the fuel injection period. .

  In addition, when changing the fuel injection period, it is desirable to reduce the NOx emission amount. Therefore, when changing the fuel injection period, it is determined whether exhaust gas recirculation (EGR) is possible (step S5). If EGR is possible, change the exhaust gas recirculation rate. On the other hand, when EGR is impossible and there is a possibility that the NOx emission amount may increase due to a change in the fuel injection timing or the fuel injection pressure, the normal fuel injection control is performed without performing the control for changing the fuel injection timing. (Step S9). Even when EGR is not possible, if it is certain that the NOx emission amount will not exceed the regulation value due to the change of the fuel injection timing, the control for changing the fuel injection timing or the fuel injection pressure according to the present embodiment is performed. Do.

  The condition under which EGR is possible is that the exhaust pressure of the engine 2 is higher than the supply air pressure. The relationship between the exhaust pressure of the engine 2 and the supply air pressure can be determined from the operating conditions of the engine 2 (for example, the rotational speed, load, etc.). Therefore, by knowing whether EGR is possible in relation to the operating conditions (for example, rotation speed, load, etc.) of the engine 2 through product tests, etc. conducted in advance, register whether EGR is possible in the control map. deep. Alternatively, an air supply pressure sensor and an exhaust pressure sensor may be installed to determine whether EGR is possible based on values detected by the sensors.

  In order to enhance the performance of the engine 2, under the condition that the load of the engine 2 is high (for example, 80% or more), the upper limit value of the fuel injection pressure, that is, the maximum value of the controllable pressure is often used. In this case, it is difficult to shorten the fuel injection period by increasing the fuel injection pressure. Therefore, under a high load condition where it is difficult to adjust the fuel injection pressure, control is performed to change the start timing and end timing of the fuel injection period while maintaining the fuel injection pressure.

  Therefore, it is determined whether or not the fuel injection pressure can be increased in relation to a predetermined maximum fuel injection pressure (step S6).

  When the fuel injection pressure can be increased in relation to the predetermined maximum fuel injection pressure, the actual fuel injection pressure is increased while maintaining the actual fuel injection start timing to shorten the fuel injection period (step S7). As a result, the actual fuel injection end timing is changed, that is, advanced, and fuel is injected during a predetermined reference fuel injection period. At this time, the recirculation rate of the exhaust gas is also changed (step S7).

  On the other hand, when the fuel injection pressure cannot be increased in relation to the predetermined maximum fuel injection pressure, control is performed to change the start timing and end timing of the fuel injection period while maintaining the fuel injection pressure (step S8). In this case, the fuel distribution ratio inside and outside the cavity 12 is maintained to be the same as the fuel distribution ratio in the reference fuel injection period. Thereby, deterioration of the soot discharge amount can be suppressed as much as possible. At this time, the exhaust gas recirculation rate is also changed (step S8).

  Specifically, as shown in FIG. 2, the crank angle B serving as a boundary between the injected fuel entering and not entering the cavity 12 is determined from the fuel injection direction from the injector 9 and the geometric shape of the cavity 12. To grasp. The fuel injection start crank angle is A, and the fuel injection end crank angle is C. At this time, the relationship between the fuel injection (driving current) and the crank angle is as shown in FIG.

  Before the injector 9 deteriorates, the fuel injection period is shorter than after the deterioration. On the other hand, if the injector 9 deteriorates, the fuel injection period becomes longer, and the fuel injection end timing (C) is delayed when the fuel injection start timing (A) is not changed. In the present embodiment, when the fuel injection period is prolonged due to deterioration of the injector 9, the ratio of | A−B | / | B−C | is the same between the actual fuel injection period and the reference fuel injection period. Thus, the fuel injection start crank angle A is advanced. At this time, the length of the actual fuel injection period is maintained.

  In the actual fuel injection period, the fuel injection start crank angle A is advanced and the ratio of (A−B) / (B−C) becomes the same as that in the reference fuel injection period. The ratio is the same as the fuel distribution ratio in the reference fuel injection period. As a result, it is possible to prevent the ratio of (A−B) / (B−C) from being different from the reference fuel injection period because the fuel injection period is prolonged and the fuel injection end crank angle C is retarded. As a result, even if the fuel injection period is extended, the deterioration of the soot emission can be suppressed as much as possible.

Hereinafter, the NOx emission amount control will be further described.
When EGR is possible and when the exhaust gas recirculation rate is changed, it is desirable to change the exhaust gas recirculation rate so that the NOx emission amount is equal to or less than that before the injector 9 is deteriorated, that is, when the product is completed. . The relationship between the fuel injection pressure or fuel injection timing, the NOx emission amount, and the exhaust gas recirculation rate (the opening degree of the EGR valve) is grasped and registered as a control map by a product test or the like that is performed in advance. Based on the control map, the opening degree of the EGR valve is adjusted based on the fuel injection pressure and the fuel injection timing correction amount set by the control according to this embodiment so that the NOx emission amount becomes a predetermined value or less. To do.

  Thereby, even when the fuel injection pressure or the fuel injection timing is changed by the correction, the NOx emission amount becomes equal to or less than that at the time of product completion. FIG. 6 shows the relationship between the soot emission amount and the NOx emission amount. When the soot discharge amount increases due to the deterioration of the injector 9 (a), the soot discharge amount can be reduced (b-1, b-2) by the fuel injection control of the present embodiment described above. On the other hand, the NOx emission amount may increase due to the change of the fuel injection timing or the fuel injection pressure (b-1, b-2). Note that the values of b-1 and b-2 are examples, and the vertical relationship may be opposite. On the other hand, the NOx emission amount is predetermined by adjusting the opening degree of the EGR valve based on the fuel injection pressure and the fuel injection timing correction amount set by the control according to the present embodiment based on the control map. (C).

  As described above, according to the present embodiment, the actual fuel injection period in the fuel injection device is acquired, compared with a predetermined threshold value, and the amount of soot generated by fuel combustion is suppressed based on the comparison result. Thus, the fuel injection period is determined. Then, the fuel injection device is controlled to inject fuel based on the determined injection period. As a result, since the fuel is injected during the fuel injection period, even if the fuel injection period deviates from the initial period due to deterioration over time, the fuel can be injected at an appropriate timing, and soot generated by the combustion of the fuel. Can be suppressed.

  Therefore, costs and labor can be reduced as compared with the case where the fuel injection device such as the injector 9 is replaced. Moreover, since the generation amount of soot is suppressed, the frequency of the DPF regeneration process, that is, the fuel consumption amount can be reduced, and the dependency on the DPF can be reduced.

  In the above embodiment, the normal fuel injection control is performed under the low load (or no load) operating condition, but the present invention is not limited to this example. Even under low load (or no load) operating conditions, fuel injection control according to the present embodiment, which will be described later, may be performed.

1: Exhaust gas recirculation system 2: Engine 3: Supercharger 3A: Compressor 3B: Turbine 3C: Rotating shaft 5: Intake passage 6: Exhaust passage 7: Recirculation passage 8: Cylinder 9: Injector 10: Combustion Chamber 11: Piston 12: Cavity 13: Intercooler 14: EGR cooler 15: EGR valve 20: Control unit 21: Acquisition unit 22: First comparison unit 23: First determination unit 24: Load detection unit 25: Second comparison unit 26 : First determination unit 27: Injection control unit 28: Second determination unit 29: Second determination unit 30: Recirculation control unit 40: Memory

Claims (5)

A fuel injection control device for controlling a fuel injection device of an engine having a cylinder and a piston reciprocating in the cylinder, wherein a concave portion forming a part of a combustion chamber is formed at the top of the piston,
An acquisition unit for acquiring an actual fuel injection period in the fuel injection device;
A first comparison unit that compares the actual fuel injection period acquired by the acquisition unit with a predetermined threshold;
A first determining unit that determines an injection period of the fuel to be injected into the combustion chamber so as to suppress the amount of soot generated by the combustion of the fuel based on the comparison result in the first comparing unit;
An injection control unit that controls the fuel injection device to inject the fuel based on the injection period determined by the first determination unit;
A fuel injection control device comprising: A load detector for detecting engine load;
A second comparison unit that compares the engine load detected by the load detection unit with a predetermined first threshold;
A first determination unit configured to determine whether correction for increasing the actual fuel injection pressure in relation to a predetermined maximum fuel injection pressure can be performed based on a comparison result in the second comparison unit;
With
When it is determined by the first determination unit that the actual fuel injection pressure cannot be increased, the injection control unit maintains the actual fuel injection pressure and during the injection period determined by the first determination unit. The fuel injection device is controlled to inject the fuel on the basis of the fuel injection device, and when the first determination unit determines that the actual fuel injection pressure can be increased, the injection control unit controls the actual fuel injection pressure. The fuel injection control device according to claim 1, wherein the actual fuel injection period is shortened. The second comparison unit compares the engine load detected by the load detection unit with a predetermined second threshold value,
The first determination unit determines whether or not the actual fuel injection period or the actual fuel injection pressure needs to be corrected based on the comparison result in the second comparison unit,
3. The actual fuel injection period or the actual fuel injection pressure is maintained when the first determination unit determines that the correction of the actual fuel injection period or the actual fuel injection pressure is unnecessary. A fuel injection control device according to claim 1. An exhaust gas recirculation unit for mixing exhaust gas discharged from the engine with combustion air;
A second determination unit for determining whether or not exhaust gas recirculation by the exhaust gas recirculation unit is possible;
A second determination unit that determines an amount of exhaust gas to be recirculated when it is determined in the second determination unit that the exhaust gas recirculation unit can recirculate the exhaust gas;
A fuel injection control device according to any one of claims 1 to 3. A fuel injection control method for controlling a fuel injection device of a diesel engine having a cylinder and a piston reciprocating in the cylinder, wherein a concave portion forming a part of a combustion chamber is formed at the top of the piston,
An acquisition unit acquiring an actual fuel injection period in the fuel injection device; and
A first comparing unit comparing the fuel injection period acquired by the acquiring unit with a predetermined threshold;
A first determining unit determining an injection period of the fuel to be injected into the combustion chamber based on a comparison result in the first comparing unit so as to suppress a generation amount of soot generated by fuel combustion; ,
An injection control unit controlling the fuel injection device to inject the fuel based on the injection period determined by the first determination unit;
A fuel injection control method comprising:

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