JP2012082800A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively improve heat efficiency of an engine, by restraining an increase in cylinder internal pressure in high load operation, in a control device of an internal combustion engine.SOLUTION: The control device 1 of the internal combustion engine 2 having a multistage injection device 30 which can inject a plurality of times including main injection in one combustion stroke, includes operation state detecting means 32 and 33 for detecting an operation state of the internal combustion engine 2, and an injection control means 50 for controlling the multistage injection device 30 so that injection of fuel by the main injection is separately performed in at least three stages, when the operation state of the internal combustion engine 2 is a predetermined high load area based on detection of the operation state detecting means 32 and 33.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine having a multi-stage injection device capable of performing a plurality of injections including a main injection during one combustion stroke.

  As a fuel injection device for an internal combustion engine (hereinafter referred to as an engine) such as a diesel engine, a plurality of pressurized fuels accumulated in a common rail are provided corresponding to each cylinder so as to supply fuel into each cylinder of the engine. 2. Description of the Related Art An accumulator fuel injection device that supplies fuel via a fuel injection control valve is known.

  For example, Patent Document 1 discloses a pressure accumulation type fuel injection device including a fuel pressurizing pump, a common rail, and a fuel injection control valve as this type of fuel injection device.

Japanese Patent Laid-Open No. 10-30486

  In an engine having an accumulator fuel injection device, multistage injection is performed in which fuel is injected a plurality of times during one combustion stroke of the engine in order to simultaneously achieve low noise and low smoke of the engine. For example, as shown in FIG. 9B, the fuel injection pattern by the multi-stage injection is performed during one combustion stroke in the operation region where the maximum in-cylinder pressure of the engine is low (see region 4 in FIG. 9A). A plurality of fuel injections including pre-injection and main injection are performed. On the other hand, in an operation region where the maximum in-cylinder pressure including the engine rated point is high (see region 1 in FIG. 9A, etc.), it is common to perform main injection only once during one combustion stroke.

  By the way, when the engine is supercharged during high-load operation or the like, the in-cylinder pressure increases at the same time as the output of the engine increases. Therefore, at the time of high load operation where the in-cylinder pressure of the engine becomes high, it is necessary to lower the compression ratio of the engine from the viewpoint of durability of the cylinder head, the cylinder block, the piston, and the like.

  However, if the compression ratio of the engine is lowered, the thermal efficiency of the engine is lowered, and the fuel consumption of the engine may be deteriorated.

  The present invention has been made in view of these points, and an object thereof is to effectively improve the thermal efficiency of the engine while suppressing an increase in the in-cylinder pressure during high-load operation of the engine.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention is a control device for an internal combustion engine having a multistage injection device capable of performing a plurality of injections including a main injection during one combustion stroke. When the operating state of the internal combustion engine is in a predetermined high load region based on the detection of the operating state, and the operating state detecting means for detecting the operating state of the fuel, at least three stages of fuel injection by the main injection And an injection control means for controlling the multistage injection device so as to be performed separately.

  Further, the injection control means performs the first stage injection timing in the vicinity of the top dead center of the internal combustion engine among the fuel injections by the main injection performed in at least three stages, and the first stage injection amount. The multi-stage injection device may be controlled so that the injection amount is smaller than the injection amount after the second stage.

  According to the control device for an internal combustion engine of the present invention, it is possible to effectively improve the thermal efficiency of the engine while suppressing an increase in the in-cylinder pressure during high load operation of the engine.

1 is a schematic overall configuration diagram showing a control device for an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the relationship between the net average effective pressure (BMEP) of the internal combustion engine which concerns on one Embodiment of this invention, and an engine speed. In the control apparatus for an internal combustion engine according to one embodiment of the present invention, it is a diagram showing a fuel injection amount and an injection timing when main injection is divided into 4 to 6 stages. It is a flow which shows the fuel-injection control by the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is a shiatsu diagram which shows the relationship between the cylinder pressure by the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention, and a crank angle. It is a PV diagram by a control device of an internal-combustion engine concerning one embodiment of the present invention. It is a figure which shows the heat release rate by the control apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is the figure which compared the case where the fuel injection by main injection is made into 1 step, and the case where it made it to 3 steps. It is a figure which shows the injection pattern by the conventional multistage injection apparatus.

  Hereinafter, based on FIGS. 1-8, the control apparatus 1 of the internal combustion engine which concerns on one Embodiment of this invention is demonstrated. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  An internal combustion engine control apparatus 1 according to an embodiment of the present invention is applied to a diesel engine (hereinafter referred to as an engine) 2 having four cylinders 2a to 2d as shown in FIG. Further, the engine 2 is provided with a multistage injection device 30 capable of performing fuel injection a plurality of times including main injection during one combustion stroke.

  As shown in FIG. 1, an intake manifold 15 for introducing fresh air through an intake passage 20 by opening an intake valve (not shown) is connected to the intake ports of the cylinders 2a to 2d of the engine 2. . Further, an exhaust manifold 16 that exhausts exhaust gas through an exhaust passage 26 by opening an exhaust valve (not shown) is connected to the exhaust ports of the cylinders 2 a to 2 d of the engine 2. Further, the intake manifold 15 and the exhaust manifold 16 are communicated with each other by an EGR passage 40 that recirculates a part of the exhaust gas.

  As shown in FIG. 1, an air cleaner 25, a compressor 23 a that constitutes a turbocharger 23, and an intercooler 22 are provided in the intake passage 20 in order from the upstream side. The exhaust passage 26 is provided with a turbine 23b that constitutes the turbocharger 23.

  As shown in FIG. 1, the multistage injection device 30 includes electromagnetic fuel injection control valves 3 a to 3 d, fuel injection pipes 4 a to 4 d, a common rail 10, and a supply pump 14.

  The fuel injection control valves 3a to 3d directly inject pressurized fuel into the cylinders 2a to 2d of the engine 2, and are slidable within the fuel injection nozzle (not shown) having injection holes and the fuel injection nozzle. And a solenoid valve (not shown) for moving the core valve in the valve opening direction. The fuel injection control valves 3a to 3d are connected to the common rail 10 via fuel injection pipes 4a to 4d. Then, when a control signal (pulse signal) is output from the ECU 50, which will be described later, to the solenoid valve, the fuel injection control valves 3a to 3d drive the core valve in accordance with the output, thereby providing an appropriate amount for each cylinder 2a to 2d. The pressurized fuel is configured to be injected.

  The common rail 10 pressure-accumulates the pressurized fuel supplied from the supply pump 14, and distributes this pressurized fuel to the fuel injection control valves 3a to 3d via the fuel injection pipes 4a to 4d.

  The supply pump 14 is a known high-pressure supply pump, and includes a feed pump that draws fuel from a fuel tank (not shown), an electromagnetic valve (not shown) that adjusts the discharge amount of pressurized fuel to the common rail 10, and the like. ing.

  The engine rotation sensor 32 detects the number of rotations of the engine 2 and is connected to the ECU 50 via electric wiring as shown in FIG.

  The accelerator opening sensor 33 detects the amount of depression of an accelerator pedal (not shown), and is connected to the ECU 50 via electric wiring as shown in FIG.

  Note that the engine rotation sensor 32 and the accelerator opening sensor 33 according to the present embodiment constitute an operating state detection means of the present invention.

  An ECU (Electric Control Unit: ECU) 50 corresponds to the injection control means of the present invention, and includes a known CPU, ROM, RAM, input port, output port, and the like. Further, the ECU 50 is configured such that output signals from various sensors such as the engine speed sensor 32, the accelerator opening sensor 33, and the crank angle sensor (not shown) are input after A / D conversion. Further, the ECU 50 includes an operating state determination unit 51 and a fuel injection condition setting unit 52 as a part of functional elements. In the present embodiment, these functional elements are described as being included in the ECU 50, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.

The operation state determination unit 51 is a parameter indicating the operation state of the engine 2 such as a detection value of the engine rotation sensor 32 (hereinafter referred to as the rotational speed N) and a detection value of the accelerator opening sensor 33 (hereinafter referred to as the accelerator opening Q). Based on the above, it is determined whether or not the operating state of the engine 2 is in a predetermined high-load operating region. Here, for example, as shown in FIG. 2, the predetermined high load operation region is set to an operation region in which the net mean effective pressure (BMEP) of the engine 2 is higher than the upper limit threshold P _MAX . . That is, the operating condition determining section 51, the rotational speed N becomes larger than the predetermined rotational speed N _S, and the accelerator opening Q also be greater than the predetermined opening Q _S, so that the BMEP is higher than the upper threshold P _MAX In the case of a proper operation region, it is determined that the operation state of the engine 2 is in a predetermined high load operation region. On the other hand, the operating condition determining section 51, the rotational speed N becomes less than the predetermined rotational speed N _S, and the accelerator opening Q also be equal to or less than a predetermined opening degree Q _S, so that the BMEP is equal to or less than the upper threshold value P _MAX In the case of a proper operation region, it is determined that the operation state of the engine 2 is not in the predetermined high load operation region.

  The fuel injection condition setting unit 52 sets the fuel injection condition by the multistage injection device 30 according to the determination of the operation state determination unit 51. When the operation state of the engine 2 is not in the predetermined high load operation region, pilot injection performed during one combustion stroke based on the operation state of the engine 2 and a characteristic map of multistage injection (not shown) stored in advance in the ECU 50, Each injection condition (fuel injection amount, injection start timing, etc.) such as main injection and after injection is set, and pulse signals of these set injection conditions are output to the solenoid valves of the fuel injection control valves 3a to 3d.

  On the other hand, when the operation state of the engine 2 is in a predetermined high load operation region, the total injection amount M of the main injection during one combustion stroke corresponding to the operation state of the engine 2 is calculated, and the fuel injection by the main injection is performed. The main injection conditions to be performed in three stages are set. And the set main injection conditions are output to the solenoid valves of the fuel injection control valves 3a to 3d as control signals (pulse signals). Here, in the present embodiment, of the main injection conditions in which the main injection is divided into three stages, the first stage fuel injection amount is set to about 5% of the calculated total injection amount M, and the injection timing (crank The angle) is set in the vicinity of the top dead center where the crank angle is as close to 0 (zero) as possible. The fuel injection amount at the second stage is set to about 70% of the calculated total injection amount M, and the injection timing (crank angle) is set around 5 ° (5 °) after top dead center. Further, the third-stage fuel injection amount is set to about 25% of the calculated total injection amount M, and the injection timing (crank angle) is set to about 10 ° (10 degrees) after the top dead center.

  It should be noted that the number of stages for dividing the main injection is not necessarily limited to three stages, and can be appropriately modified and applied as long as the number of stages is three or more, such as 4 to 6 stages. In this case, the fuel injection amount of the first stage performed near the top dead center is calculated by the following formula 1, and the fuel after the second stage performed within the range of 10 ° (10 degrees) after the top dead center from the vicinity of the top dead center. The injection amount is calculated by the following formula 2.

  In addition, A and B in Formulas 1 and 2 are calculated by Formulas 3 and 4 below. Further, n in Equations 3 and 4 indicates the number of stages that separate the main injection (n ≧ 3), and k indicates the order in which the fuel is injected (1 ≦ k ≦ n).

  Further, the injection timing (crank angle) after the second stage performed in the range from the vicinity of the top dead center to 10 ° (10 degrees) after the top dead center is calculated by the following Expression 5.

  As described above, when the injection timing and the injection amount when the number of stages for dividing the main injection is set to four or more are calculated based on the above formulas 1 to 5, the relationship shown in Table 1 of FIG. 3 is obtained. In either case, the first stage fuel injection amount performed in the vicinity of the top dead center is about 3 to 7% of the total injection amount M, and is set smaller than the fuel injection amount performed after the second stage.

  Since the control apparatus 1 for an internal combustion engine according to one embodiment of the present invention is configured as described above, for example, the following control is performed according to the flow shown in FIG.

In step (hereinafter, the step is simply referred to as S) 100, the operation state determination unit 51 of the ECU 50 determines whether or not the operation state of the engine 2 is in a predetermined high load operation region. Rotational speed N is greater than the predetermined rotational speed N _S, and becomes larger than the predetermined opening degree Q _S accelerator opening Q, if BMEP is operating range such that higher than the upper limit threshold value P _MAX, the operation state of the engine 2 Is determined to be a predetermined high-load operation region, and the process proceeds to S110. On the other hand, at a rotational speed N is less than a predetermined rotational speed N _S, and also the accelerator opening Q becomes equal to or less than the predetermined opening Q _S, if BMEP is operating range such that less than the upper limit threshold value P _MAX, the operation of the engine 2 The state is determined not to be in the predetermined high load operation region, and the process proceeds to S200.

  In S <b> 110, the fuel injection condition setting unit 52 calculates the total injection amount M of main injection performed in three stages based on the operating state of the engine 2.

  In S120, the fuel injection condition setting unit 52 sets main injection conditions (each fuel injection amount, each injection timing) up to the first to third stages based on the total injection amount M calculated in S110. Specifically, the first-stage fuel injection amount performed near the top dead center is set to about 5% of the total injection amount M. Further, the second stage fuel injection amount performed around 5 ° (5 degrees) after the top dead center is set to about 70% of the total injection amount M. Further, the third stage fuel injection amount performed around 10 ° (10 degrees) after the top dead center is set to about 25% of the total injection amount M.

  In S130, the pulse signal of the main injection condition set in S120 is output from the fuel injection condition setting unit 52 to the electromagnetic valves of the fuel injection control valves 3a to 3d, and this control is returned.

  On the other hand, if it is determined in S100 described above that the operating state of the engine 2 is not in the predetermined high-load operating region, the operating state of the engine 2 and the multi-stage injection characteristic map are determined by the fuel injection condition setting unit 52 in S200. Each injection condition such as pilot injection, main injection, and after injection performed during one combustion stroke is set based on the above.

  In S210, the pulse signal of each injection condition set in S200 is output from the fuel injection condition setting unit 52 to the electromagnetic valves of the fuel injection control valves 3a to 3d, and this control is returned.

  With the configuration as described above, the control device 1 for an internal combustion engine according to one embodiment of the present invention has the following operations and effects.

  When the operating state of the engine 2 is in a predetermined high-load operating region where the net average effective pressure (BMEP) is high, the fuel injection of the main injection by the multistage injection device 30 is injected in three stages. In the first stage, about 5% of the total injection amount M is injected near top dead center, and in the second stage, about 70% of the total injection amount M is injected around 5 ° (5 degrees) after top dead center. In the third stage, about 25% of the total injection amount M of fuel is injected around 10 ° (10 degrees) after top dead center.

  FIG. 5 shows an acupressure diagram showing the relationship between the in-cylinder pressure of the engine 2 and the crank angle when the main injection is injected in three stages. Moreover, a PV diagram is shown in FIG. 6, and a diagram showing a heat generation rate is shown in FIG. As shown in FIG. 5, in the case of the present embodiment in which the main injection is divided into three stages (solid line) compared to the conventional example in which the main injection is only one stage (broken line), an increase in the in-cylinder pressure of the engine 2 is effective It can be seen that it is suppressed. Further, as shown in FIG. 6, in the case of the present embodiment in which the main injection is divided into three stages (solid line) as compared with the conventional example (dashed line) in which the main injection is only one stage, the area of the PV diagram is shown. Is increased (see region A in FIG. 6), it can be seen that the torque that is the output of the engine 2 is effectively increased. Furthermore, as shown in FIG. 7, in the conventional example (dashed line) in which the main injection is only one stage, heat is generated only once during one combustion stroke, whereas the main injection is divided into three stages. In the case of the form (solid line), it can be seen that heat is generated three times during one combustion stroke.

  That is, according to the control apparatus 1 for an internal combustion engine according to an embodiment of the present invention, when the operating state of the engine 2 is in a predetermined high load operation region, the fuel injection of the main injection is divided into three stages. Thus, it is possible to increase the output of the engine 2 while effectively suppressing an increase in the in-cylinder pressure of the engine 2.

  In addition, since heat is generated three times during one combustion stroke of the engine 2 and the thermal efficiency of the engine 2 is improved, the fuel consumption of the engine 2 can be effectively improved.

  Here, as a comparative example of the conventional example in which the main injection is only one stage and the present embodiment in which the main injection is divided into three stages, the maximum in-cylinder pressure of the engine 2, the output of the engine 2, the fuel consumption of the engine 2 (BSFC) ), Smoke (FSN) discharged from the engine 2 is shown in FIGS. As shown in FIGS. 8A to 8D, according to the present embodiment in which the main injection is divided into three stages, the maximum in-cylinder pressure of the engine 2 decreases and the output of the engine 2 increases compared to the conventional example. The fuel efficiency (BSFC) of the engine 2 is improved, and the smoke (FSN) discharged from the engine 2 is also reduced, so that the effect of the present invention can be seen.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, in the above-described embodiment, the control apparatus 1 for an internal combustion engine has been described as being applied to a four-cylinder engine 2; Can do.

  In addition, the main injection conditions (fuel injection amount, injection timing) in the case of dividing the main injection into four or more stages have been described as being calculated by the above formulas 1 to 5, but Table 1 of FIG. You may make it memorize | store as an injection condition map and set the optimal main injection conditions according to the driving | running state of the engine 2 by referring to the injection condition map concerned.

2 Engine (Internal combustion engine)
3a, 3b, 3c, 3d Fuel injection control valve (multistage injection device)
4a, 4b, 4c, 4d Fuel injection pipe (multistage injection device)
10 Common rail (multi-stage injection device)
14 Supply pump (multistage injection device)
30 Multistage injection device 32 Engine rotation sensor (operating state detection means)
33 Accelerator opening sensor (operating state detection means)
50 ECU (injection control means)
51 Operation state determination unit 52 Fuel injection condition setting unit

Claims (2)

A control device for an internal combustion engine having a multi-stage injection device capable of performing a plurality of injections including a main injection during one combustion stroke,
An operating state detecting means for detecting an operating state of the internal combustion engine;
Based on the detection of the operating state detecting means, when the operating state of the internal combustion engine is in a predetermined high load region, the multi-stage injection device is arranged so that fuel injection by the main injection is performed in at least three stages. An internal combustion engine control apparatus comprising: an injection control means for controlling. The injection control means includes
Of the fuel injection by the main injection performed in at least three stages, the first stage injection timing is performed in the vicinity of the top dead center of the internal combustion engine, and the first stage injection quantity is the second and subsequent stage injection quantity. The control apparatus for an internal combustion engine according to claim 1, wherein the multistage injection device is controlled to be smaller.

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