JP5206161B2 - Engine control apparatus and control method - Google Patents

Description

  The present invention relates to engine control technology, and more particularly to fuel injection control technology.

  In diesel engines, reducing smoke generation is one of the challenges. As a method for reducing smoke, a split injection method has been proposed in which fuel injected during one combustion is divided and injected (Patent Document 1). In the split injection method, split injection is performed a plurality of times within a short period after the main fuel injection. As a result, the injection amount at the time of main injection can be reduced, and afterburning combustion can be promoted by split injection, so that unburned fuel can be reduced and the generation of smoke can be reduced.

JP-A-62-75051

  The fuel injection timing is set on the basis of the crank angle so that optimum combustion efficiency and the like can be obtained according to the operation region of the diesel engine. However, the crankshaft may cause a slight rotational change due to torque fluctuation. On the other hand, when split injection is performed a plurality of times within a short period, it takes time corresponding to the injection amount from the start of fuel injection to the completion of injection.

  Accordingly, if the injection timing of split injection is set with reference to the crank angle, the time interval of each split injection may vary due to the influence of a slight change in the rotation of the crankshaft. If the time interval of each split injection varies, there may occur a case where the injection timing of the subsequent split injection comes before the completion of the injection of the preceding split injection. This causes a variation in the fuel injection amount, reduces the smoke reduction effect, and adversely affects the fuel consumption.

  An object of the present invention is to reduce variation in injection amount due to split injection.

According to the present invention, the injection timing setting means for setting the injection timing of the main injection of fuel and the injection timing of each of the plurality of split injections after the main injection, and the main timing set by the injection timing setting means And an injection execution means for injecting fuel at the injection timing of each of the split injections, wherein the injection timing setting means counts a timer from a predetermined timing start point corresponding to the injection start timing. The main injection timing is set based on the crank angle of the engine, and the split injection timing is determined as the injection timing of the split injection for the second and subsequent split injections. set in time to occur after a predetermined time has elapsed from completion, the injection execution means, counting of the clock means and the injection timing set by the time Based on the control device for an engine, characterized in that to inject fuel according to the split injection is provided.

  In the present invention, the injection timing of the second and subsequent split injections is set based on the time instead of the crank angle, thereby eliminating the influence of the crankshaft rotation change and securing the injection time of each split injection. Thereby, the dispersion | variation in the injection quantity by split injection can be reduced.

  In the present invention, the injection timing setting means preferably sets the injection timing of the first split injection by the crank angle of the engine. It is possible to more reliably promote afterburning and prevent adverse effects on torque.

  In the present invention, the split injection may be performed only when the operating region of the engine is in a predetermined operating region. In the split injection method, an error in the total injection amount is likely to occur due to the increase in the number of fuel injections. Therefore, by performing split injection only in the operation region where smoke is likely to occur, an error in the injection amount in other operation regions occurs. Can be suppressed.

Further, according to the present invention, the fuel injection timing is set in the injection timing setting step for setting the injection timing of the main injection of the fuel and the injection timing of each of the plurality of split injections after the main injection, and the injection timing setting step. An injection execution step of injecting fuel at the injection timing of the main injection and each of the split injections, and a timing step of starting a timer from a predetermined timing start point corresponding to the injection start timing In the injection timing setting step, the injection timing of the main injection is set based on the crank angle of the engine, while the split injection is preceded by the split injection prior to the split injection. the set time to occur after a predetermined time has elapsed from the injection completion, in the injection execution process, before and set injection timing at the time Based on the count of the counting process, the control method for an engine, characterized in that to inject fuel according to the split injection is provided.

  As described above, according to the present invention, it is possible to reduce variations in the injection amount due to split injection.

<Device configuration>
FIG. 1 is a block diagram of an engine control apparatus A according to an embodiment of the present invention. In the present embodiment, the control device A controls the operation of the four-cycle diesel engine 10. In the present embodiment, an example in which the present invention is applied to the control of a diesel engine is illustrated, but the present invention is also applicable to, for example, a gasoline engine using compression self-ignition control.

  The diesel engine 10 includes a cylinder block 11 and a cylinder head 12. A cylinder (cylinder) in which the piston 13 slides is formed in the cylinder block 12, and the reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 14. The rotation angle of the crankshaft 14 is detected by a crank angle sensor 41.

  A combustion chamber is formed between the cylinder block 11 and the cylinder head 12. A water jacket through which the cooling water passes is provided in the cylinder block 11, and a water temperature sensor 42 that detects the water temperature of the cooling water that passes through the water jacket is provided in the cylinder block 11.

  The cylinder head 12 includes an intake port 15 and an exhaust port 17 communicating with the combustion chamber 31. The intake port 15 is opened and closed by an intake valve 16, and the exhaust port 17 is opened and closed by an exhaust valve 18. The cylinder head 12 is also provided with an electronically controlled fuel injection valve 19 that injects fuel into the combustion chamber. The fuel injection valve 19 injects fuel into the combustion chamber in the vicinity of the top dead center of the compression stroke, whereby the air-fuel mixture self-ignites.

  An intake passage 20 communicates with the intake port 15. An air filter 21, an intercooler 22, an electronically controlled throttle valve 23, an intake air temperature sensor 24, and an intake air pressure (supercharging pressure) sensor 25 are provided in the intake passage 20 from the upstream side. An exhaust passage 30 communicates with the exhaust port 17. An oxidation catalyst 32 and a particulate filter 31 are provided in the exhaust passage 30 from the upstream side.

  A turbocharger 40 is provided between the intake passage 20 and the exhaust passage 30 and supercharges intake air using exhaust pressure. Further, the intake passage 20 and the exhaust passage 30 communicate with each other through an EGR passage 50. The EGR passage 50 is provided with an EGR cooler 51 and an electronically controlled EGR valve 52. When the EGR valve 52 is opened, a part of the exhaust gas is recirculated to the intake passage 20 through the EGR passage 50, and generation of nitrogen oxides can be reduced due to a decrease in the combustion temperature.

  The ECU 100 includes a CPU 101, a ROM 102, a RAM 103, and an I / F (interface) 104. The CPU 101 executes a control program stored in the ROM 102 to control the diesel engine 10. In addition to the program executed by the CPU 101, the ROM 102 stores information such as the fuel injection timing and the fuel injection amount set according to the operating state of the diesel engine 10. The RAM 103 stores temporary data. The ROM 102 and RAM 103 may be other storage means.

  The I / F 104 includes a crank angle sensor 41, a water temperature sensor 42, an intake air temperature sensor 24, an intake pressure sensor 25, an accelerator pedal sensor 43 that detects an operation amount with respect to an accelerator pedal, and a brake pedal sensor that detects an operation of a driver with respect to a brake pedal. 44 detection results are input, and the CPU 101 can read them. A control command from the CPU 101 is output to the fuel injection valve 19, the throttle valve 23, and the EGR valve 52 via the I / F 104. The amount of fuel injected by the fuel injection valve 19 is controlled by, for example, the width of the pulse signal to the fuel injection valve 19.

<Split injection timing>
FIG. 2 is an explanatory diagram of the injection timing of split injection in the present embodiment. In the example of the figure, it is assumed that after the main fuel injection, three split injections # 1 to # 3 are performed. However, the number of split injections is not limited to this, and the number of split injections may be two or four or more. Good.

  The injection timing of the main injection is set with reference to the crank angle of the crankshaft 14. In the example of the figure, the injection timing (injection start timing) is set to an angle θm slightly before the top dead center of the compression stroke.

  In the present embodiment, among the split injections # 1 to # 3, the injection timing of the first split injection # 1 is set with reference to the crank angle, and the injection timing is set to an angle θs1 corresponding to the completion of the main injection. (Injection start time) is set.

  On the other hand, the injection timings of the second and subsequent split injections # 2 and # 3 are set on the basis of time, and are set to be performed after a predetermined time (hereinafter referred to as interval time) has elapsed since the completion of injection of the preceding split injection. . In the case of the example in the figure, the injection timing (injection start timing) is set for the split injection # 2 after an interval time: ts2 has elapsed since the completion of the injection of the preceding split injection # 1. In addition, for the split injection # 3, the injection timing (injection start timing) is set after the elapse of the interval time: ts3 from the completion of the injection of the preceding split injection # 2. Here, ts2 ≧ 0 and ts3 ≧ 0, and ts2 and ts3 may be the same or different.

  An example of setting the injection timing of split injections # 2 and # 3 will be specifically described. Since these injection timings are based on time, a timing start point is required. In the present embodiment, the crank timing θs1 that is the injection timing of the split injection # 1 is used as a reference, and is set as a timer timing start point (T = 0).

Assuming that the injection time from the start of split injection # 1 to the completion of injection is ti1, the injection timing (injection start timing) T2 of split injection # 2 is
T2 = ti1 + ts2
It is. Assuming that the injection time ti1 is proportional to the set injection amount (tv1) of the split injection # 1, ti1 = tv1 × C (constant).

Similarly, the injection timing (injection start timing) T3 of split injection # 3 is assumed to be ti2 as the injection time of split injection # 2.
T3 = ti1 + ts2 + ti2 + ts3
It is. The injection time ti2 is ti2 = tv2 × C (constant), where the set injection amount of split injection # 2 is tv2. In this way, the injection timing of the second and subsequent split injections can be set.

  In this embodiment, by setting the injection timing of the second and subsequent split injections based on the time instead of the crank angle, the influence of the rotational change of the crankshaft 14 is eliminated, and the injection time of each split injection is set. Secure. Thereby, the dispersion | variation in the injection quantity by split injection can be reduced.

  In the present embodiment, the injection timing of the first split injection # 1 is set with reference to the crank angle, but it can be set with reference to time as with the split injections # 2 and # 3. In this case, the timing start point of the timer is based on the crank angle θm that is the injection timing of the main injection, and the injection time of the main injection and the time from the completion of the main injection to the start of the first split injection # 1 Thus, the injection timing of the first split injection # 1 can be calculated and set.

  However, the injection timing of the first split injection is preferably based on the crank angle as shown in FIG. From the positional relationship between the progress of the combustion of the air-fuel mixture and the piston 13, it is considered that the reference to the crank angle can more reliably promote afterburning and prevent adverse effects on the torque. .

<Example of fuel injection control>
FIG. 3A is a flowchart showing an example of processing executed by the CPU 101, and particularly shows processing related to setting of fuel injection timing and execution of injection. In S1, the detection result of each sensor is acquired. In S2, it is determined whether or not the operation region of the diesel engine 10 is a predetermined operation region (split injection region). If applicable, the process proceeds to S3, and if not, the process proceeds to S4.

  In the present embodiment, the split injection described above is performed only when the operation region of the diesel engine 10 is a predetermined operation region, and normal injection (no split injection) is performed otherwise. There is an error in the fuel injection amount. When split injection is performed, an error in the total injection amount tends to occur during one combustion due to accumulation of errors in each injection. Therefore, by performing split injection only in the operation region where smoke is likely to occur, the occurrence of injection amount errors in other operation regions can be suppressed.

  The split injection region is set, for example, as a medium load region. FIG. 3B is a diagram showing a setting example of the split injection region, where the split injection region is set in a region where the required torque and the engine speed are intermediate. The engine speed is calculated based on the detection result of the crank angle sensor 41, for example. The required torque is calculated based on, for example, the engine speed and the amount of operation with respect to the accelerator pedal detected by the accelerator pedal sensor 43.

  In S3, split injection control is performed. Details will be described later. In S4, normal injection control (no split injection) is performed. Thus, one unit of processing is completed.

  FIG. 4 is a flowchart showing an example of split injection control in S3. In the figure, S11 to S13 are setting processes such as injection timing, and S14 to S24 are fuel injection execution processes.

  In S11, the fuel injection amount and the injection timing of the main injection and the first split injection are set based on the detection result of each sensor acquired in S1. These are set in advance according to the operation state of the diesel engine 10 and can be set by reading out information stored in the ROM 102. The injection timing of the main injection and the first split injection is set based on the crank angle as shown in FIG.

  In S12, the injection time is calculated from the fuel injection amount of the first split injection set in S11. The calculation method is as described above. In S13, based on the detection result of each sensor acquired in S1, the fuel injection amount and the injection timing of each split injection after the second time are set. The fuel injection amount can be set by reading the information stored in the ROM 102, and may be the same or different in the second and subsequent split injections.

  The injection timing is set based on time as shown in FIG. At that time, the interval time can be set by reading the information stored in the ROM 102, and the injection time of the second split injection is set from the read interval time and the calculation result of S12. The injection timing of the third and subsequent split injections is set in the same manner, but the injection time of the preceding split injection is calculated from the fuel injection amount of the split injection. Through the above processing, the fuel injection amount and injection timing of main injection and split injection are set, and the processing for executing fuel injection is performed according to the set contents.

  In S14, the detection result of the crank angle sensor 41 is acquired. In S15, based on the detection result acquired in S14, it is determined whether or not the injection timing of the main injection set in S11 has arrived. If applicable, the process proceeds to S16, and if not, the process returns to S14. In S16, main injection is executed. That is, a control signal corresponding to the fuel injection amount set in S11 is output to the fuel injection valve 19 to inject fuel.

  In S17, the detection result of the crank angle sensor 41 is acquired. In S18, based on the detection result acquired in S16, it is determined whether or not the injection timing of the first split injection set in S11 has come. If yes, go to S19, otherwise go back to S17. In S19, the first split injection is executed. That is, a control signal corresponding to the fuel injection amount set in S11 is output to the fuel injection valve 19 to inject fuel. In S19, a timer is started to determine the arrival of the injection timing of the second and subsequent split injections.

  In S20, the parameter: k is set to 2. The parameter k is a parameter indicating the number of split injections at present, and since the first split injection has started, the initial value is set to 2.

  In S21, it is determined whether or not the time T of the timer that started timing in S19 has reached the injection timing Tk of the k-th split injection set in S13. If applicable, the process proceeds to S22, and if not, the process returns to S21. In S22, the k-th split injection is executed. That is, a control signal corresponding to the fuel injection amount of the k-th split injection set in S13 is output to the fuel injection valve 19 to inject fuel.

  In S23, it is determined whether or not the parameter k is the parameter n. If applicable, the process of one unit is terminated. If not, the process proceeds to S24. The parameter n indicates the total number of split injections, and is 3 when three split injections are performed as in the example of FIG. The total number of split injections may be a fixed number, or may be set for each fuel injection. In S24, one value of the parameter: k is added, and the process returns to S21 to repeat the same processing. With the above processing, the main injection and the first split injection can be executed on the basis of the crank angle, and the second and subsequent split injections can be executed on the basis of the time.

1 is a block diagram of an engine control device A according to an embodiment of the present invention. FIG. It is explanatory drawing of the injection timing of split injection in this embodiment. (A) is a flowchart showing an example of processing executed by the CPU 101, (b) is a diagram showing a setting example of a split injection region. It is a flowchart which shows the example of the split injection control of S3.

Explanation of symbols

A Control device 10 Diesel engine 19 Fuel injection valve 100 ECU

Claims (4)

Injection timing setting means for setting the injection timing of the main injection of fuel and the injection timing of each of the multiple split injections after the main injection;
Injection execution means for injecting fuel at the injection timing of the main injection and the split injection set by the injection timing setting means;
In an engine control device comprising:
The injection timing setting means includes
Having time measuring means for starting the timer from a predetermined time starting point corresponding to the injection start time;
The injection timing of the main injection is set by the crank angle of the engine, and the injection timing of the second and subsequent split injections is set so that the split injection is performed after a predetermined time has elapsed since the completion of the preceding split injection. Set in time ,
The engine control apparatus according to claim 1, wherein the injection execution unit injects fuel related to the split injection based on an injection timing set by the time and a time measured by the time measuring unit.
  The engine control device according to claim 1, wherein the injection timing setting means sets the injection timing of the first split injection by a crank angle of the engine.   3. The engine control device according to claim 1, wherein the split injection is performed only when the operation region of the engine is in a predetermined operation region. 4. An injection timing setting step for setting the injection timing of the main injection of fuel and the injection timing of each of the multiple split injections after the main injection;
An injection execution step of injecting fuel at the injection timing of the main injection and the split injection set in the injection timing setting step;
In an engine control method comprising:
A timing step of starting the timer timing from a predetermined timing start point corresponding to the injection start timing,
In the injection timing setting step,
The injection timing of the main injection is set by the crank angle of the engine, and the injection timing of the second and subsequent split injections is set so that the split injection is performed after a predetermined time has elapsed since the completion of the preceding split injection. Set in time ,
In the injection execution step, the fuel related to the split injection is injected based on the injection timing set by the time and the timing of the timing step .

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