JP2014077375A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of suppressing the generation of particulates without failure such that intake stroke is completed while fuel injected in a combustion chamber is not sufficiently vaporized.SOLUTION: An injector for cylinder injection of fuel is operated intermittently in a period of intake stroke when air is sucked into a combustion chamber by lowering of a piston. A fuel injection quantity for each operation of the injector for cylinder injection of fuel is increased when a position of the piston is in the center more than when the position is on the end side.

Description

  The present invention relates to an internal combustion engine including an in-cylinder injector that directly injects fuel into a combustion chamber.

  In an internal combustion engine equipped with an in-cylinder injector that directly injects fuel into the combustion chamber, the injected fuel adheres to the piston and cylinder liner, which receives heat and becomes particulate matter, so-called particulates. There is a problem (PM; Particulate Matter) that it is discharged into the atmosphere.

  As a countermeasure, reduce the fuel injection amount when the piston position in the cylinder is high and the injected fuel tends to adhere to the piston top surface, and reduce the fuel injection amount when the piston position is low and the injected fuel is difficult to adhere to the piston top surface. An internal combustion engine in which the injection amount is increased is known (for example, Patent Document 1).

JP 2008-88856 A

  However, if the fuel injection amount is increased when the piston position is low, in the case of the intake stroke injection in which the fuel is injected during the intake stroke, the intake stroke is completed without the vaporized fuel being sufficiently vaporized and the compression stroke is started. There is a possibility of migration. If so, problems such as deterioration in fuel consumption and increase in HC (hydrocarbon) emissions occur.

  An object of the present invention is to provide an internal combustion engine capable of suppressing the generation of particulates without causing a problem that the intake stroke is terminated without sufficiently evaporating the fuel injected into the combustion chamber.

  An internal combustion engine according to a first aspect of the present invention includes a piston that reciprocates in a cylinder to form a variable-volume combustion chamber in the cylinder, an in-cylinder injector that directly injects fuel into the combustion chamber, and control means Is provided. The control means intermittently operates the in-cylinder injector during an intake stroke period in which air is sucked into the combustion chamber by the forward movement of the piston, and determines the fuel injection amount for each operation of the in-cylinder injector. Is increased when the position is on the center side rather than on the end side.

  The internal combustion engine of the invention according to claim 2 is limited to the control means of the invention according to claim 1, and the control means determines the operation time of the intermittent operation of the in-cylinder injector as the forward movement of the piston. Make the position longer when the position is in the middle than when it is in the start and end areas.

  An internal combustion engine according to a third aspect of the invention is the invention according to the first aspect, further comprising an intake pipe injection injector. The control means operates the intake pipe injection injector before the intake stroke period.

  According to the present invention, it is possible to suppress the generation of particulates without causing a problem that the intake stroke ends without the fuel injected into the combustion chamber being sufficiently vaporized.

The figure which shows the structure of the internal combustion engine of one Embodiment of this invention. The flowchart which shows the control of the same embodiment. The time chart which shows operation | movement of the in-cylinder injector in the in-cylinder injection mode of the embodiment with progress of time. The time chart which shows operation | movement of the in-cylinder injector and the in-pipe injection injector in the in-cylinder injection + intake-pipe injection mode of the embodiment with progress of time. The time chart which shows the modification of the operation | movement of FIG. The time chart which shows the modification of the operation | movement of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 10 denotes a reciprocating internal combustion engine, for example, a four-cylinder gasoline engine, which includes a main body 20, an intake pipe 31, an exhaust pipe 32, and an ECU (Electric Control Unit) 50 serving as a control unit. FIG. 1 representatively shows one of the four cylinders and a combustion chamber in the cylinder.

  The main body 20 includes a cylinder block 21 and a cylinder head 22 assembled to the cylinder block 21. The cylinder block 21 has a cylinder 23 inside. In this cylinder 23, the piston 24 connected to the crankshaft 100 via the connecting rod 101 is accommodated. The piston 24 reciprocates in the vertical direction in the cylinder 23, whereby a variable volume combustion chamber 25 is formed in the cylinder 23. Note that a part of the connecting rod 101 in the figure is omitted.

  The cylinder head 22 is provided with a spark plug 26, an intake valve 27, and an exhaust valve 28. The intake valve 27 opens and closes an intake port 29 that is formed in the cylinder head 22 and faces the combustion chamber 25. The exhaust valve 28 opens and closes an exhaust port 30 that is formed in the cylinder head 22 and faces the combustion chamber 25. The intake port 29 communicates with the intake pipe 31. The exhaust port 30 communicates with the exhaust pipe 32.

  As the piston 24 moves downward (forward), air or a mixture of air and fuel is supplied into the combustion chamber 25 through the intake port 29 (intake stroke). The intake pipe 31 is provided with an air flow meter 33 for detecting the intake air amount and a throttle valve 34 for determining the intake air amount (air amount).

  The cylinder head 22 is provided with an in-cylinder injector 35. The in-cylinder injector 35 has a fuel injection port facing the combustion chamber 25 and directly injects fuel into the combustion chamber 25. In this embodiment, one in-cylinder injector 35 is provided for each cylinder, but a plurality of in-cylinder injectors may be provided for each cylinder.

  An intake pipe injection injector 36 is provided in the intake pipe 31. The intake pipe injection injector 36 is provided in a state where the fuel injection port faces the intake port 29 and injects fuel into the intake pipe 31. In this embodiment, one intake pipe injection injector 36 is provided for each cylinder, but a plurality of intake pipe injection injectors 36 may be provided for each cylinder.

  The fuel injected from the in-cylinder injector 35 into the combustion chamber 25 is intake air or an air-fuel mixture (mixture of air and fuel) that flows into the combustion chamber 25 through the intake port 29 in the combustion chamber 25. Mixed with. The fuel injected from the intake pipe injector 36 is mixed with intake air in the intake pipe 31. This air-fuel mixture flows into the combustion chamber 25 through the intake port 29.

The air-fuel mixture in the combustion chamber 25 is compressed by the ascending (returning) of the piston 24 (compression stroke), and is ignited by the spark generated by the spark plug 26 to burn and explode (explosion stroke). The piston 24 descends due to this combustion / explosion, the exhaust valve 28 opens before the piston 24 rises again, and the gas in the combustion chamber 25 is exhausted through the exhaust port 30 (exhaust stroke). Then, the piston 24 descends again, and air or a mixture of air and fuel is supplied into the combustion chamber 25 through the intake port 29 (intake stroke).
The exhaust pipe 32 is provided with an air-fuel ratio sensor 37 that detects the air-fuel ratio of the exhaust gas, and a catalyst 38 that purifies the exhaust gas. A pressure sensor 39 is provided in the intake pipe 31. The pressure sensor 39 detects the pressure downstream of the throttle.

  A fuel tank 40 includes a feed pump 41 for sending out fuel. Fuel is fed from the feed pump 41 to the fuel pipe 42, and the fuel is supplied to the in-cylinder injector 35 by the branch pipe 43a and the high-pressure pump 44 on the branch pipe 43a. The fuel in the fuel pipe 42 is supplied to the intake pipe injector 36 by the branch pipe 43b.

  On the other hand, the ECU 50 includes an in-cylinder injector 35, an intake pipe injector 36, an air flow meter 33, a throttle valve 34, an air-fuel ratio sensor 37, a pressure sensor 39, a feed pump 41, a high-pressure pump 44, an ignition coil 45, a crank angle. A sensor 46, a coolant temperature sensor 47, an accelerator opening sensor 48, and the like are connected.

  The ignition coil 45 supplies an ignition voltage to the ignition plug 26. The crank angle sensor 46 detects the position and rotation angle of the crankshaft 100 that is interlocked with the vertical movement of the piston 24. The cooling water temperature sensor 47 detects the cooling water temperature of the main body 20. The accelerator opening sensor 48 detects the accelerator opening (the amount of depression of the accelerator pedal).

The ECU 50 includes the following means (1) to (4) as main functions.
(1) Of the in-cylinder injector 35 and the intake pipe injector 36, the in-cylinder injection mode (direct injection mode) in which only the in-cylinder injector 35 is operated, and both the in-cylinder injector 35 and the intake pipe injector 36 are operated. The internal combustion engine 10 is mounted with either the in-cylinder injection to be performed + intake pipe injection mode (direct injection + multi-point injection mode) or the intake pipe injection mode (multi-point injection mode) in which only the intake pipe injection injector 36 is operated. First control means that is selectively set in accordance with the running load (for example, required torque) of the vehicle in question and the temperature of the in-cylinder injector 35.

  (2) When the in-cylinder injection mode is set, the in-cylinder injector 35 is operated intermittently during the intake stroke period in which air is sucked into the combustion chamber 25 by the lowering (forward movement) of the piston 24 (multiple steps). Second control means that increases the fuel injection amount for each operation of the in-cylinder injector 35 when the position of the piston 24 is closer to the center than to the end. The end portions referred to here are the top dead center at the top and the bottom dead center at the bottom. The central portion is an area approximately halfway between the top dead center and the bottom dead center. The moving speed of the piston 24 is slow in the vicinity of the top dead center and the top dead center, and is the fastest in a region approximately between the top dead center and the bottom dead center. Regarding the fuel injection amount for each operation of the in-cylinder injector 35, specifically, the respective operation times of the intermittent operation of the in-cylinder injector 35 (that is, the drive pulse voltage supply time to the in-cylinder injector 35) are adjusted. You can control it.

  (3) When the in-cylinder injection + intake pipe injection mode is set, the intake pipe injection injector before the intake stroke period, that is, in the exhaust stroke in which the gas in the combustion chamber 25 is discharged by the piston 24 ascending (returning). 36, and the in-cylinder injector 35 is intermittently operated during the intake stroke period, and the fuel injection amount for each operation of the in-cylinder injector 35 is set to be more central than when the position of the piston 24 is on the end side. 3rd control means to increase when it exists in the part side.

  (4) Fourth control means for operating the intake pipe injection injector 36 during the exhaust stroke when the intake pipe injection mode is set.

Next, the control executed by the ECU 50 will be described with reference to the flowchart of FIG. 2 and the time charts of FIGS. 3 and 4.
When the in-cylinder injection mode is set (YES in step 101), as shown in FIG. 3, the in-cylinder injector 35 is intermittently operated during the intake stroke period, and each operation of the in-cylinder injector 35 is performed. Is controlled in accordance with the position of the piston 24 (step 102).

  That is, in the intake stroke period, when the position of the piston 24 is slightly away from the top dead center, the in-cylinder injector 35 is operated for a short time t1. Subsequently, when the position of the piston 24 is in an approximately middle region between the top dead center and the bottom dead center and the moving speed of the piston 24 becomes the fastest, the in-cylinder injector 35 is operated for a time t3 longer than the time t1. . Next, when the position of the piston 24 is slightly before the bottom dead center, the in-cylinder injector 35 is operated for t2 time longer than t1 time and shorter than t3 time. The relationship between t1 time, t3, and t2 time is t1 <t2 <t3.

  Here, to operate the in-cylinder injector 35 for t1 time is to supply the in-cylinder injector 35 with a drive pulse voltage that repeatedly turns on and off at a constant cycle for t1 time. Operating the in-cylinder injector 35 only for t3 time means supplying the same drive pulse voltage to the in-cylinder injector 35 for t3 time. Operating the in-cylinder injector 35 for t2 hours means supplying the same drive pulse voltage to the in-cylinder injector 35 for t2 hours. Then, the on / off duty of the drive pulse voltage is adjusted so as to supply the combustion chamber 25 with an appropriate amount of fuel commensurate with the running load of the vehicle.

  As described above, when the piston 24 is in the vicinity of the top dead center, the moving speed of the piston 24 is slow, and the fuel injected from the in-cylinder injector 35 easily reaches the cylinder liner on the inner wall of the piston 24 or the cylinder 23. In view of this, the operation time of the in-cylinder injector 35 is suppressed to a shorter t1 time, and the amount of fuel injected into the combustion chamber 25 is suppressed to a small amount. By suppressing to a small amount, the amount of fuel adhering to the piston 24 and the cylinder liner can be suppressed. As a result, generation | occurrence | production of particulate matter, what is called a particulate, can be suppressed.

  When the piston 24 approaches bottom dead center, since the intake stroke period is at the end and the next compression stroke period is near, the operating time of the in-cylinder injector 35 is suppressed to t2 hours shorter than t3 hours, and the combustion chamber 25 is moved to. Reduce the amount of fuel injection to a small amount. By suppressing the amount to a small amount, the fuel injected into the combustion chamber 25 can be sufficiently vaporized in the remaining period of the intake stroke period. If the intake stroke is completed without sufficiently evaporating the fuel injected into the combustion chamber 25 and the operation proceeds to the compression stroke, there is a possibility that the fuel consumption deteriorates and the HC (hydrocarbon) emission amount increases. Such a malfunction can be prevented in advance.

  When the piston 24 is in a region approximately between the top dead center and the bottom dead center, the moving speed of the piston 24 is the fastest, and the fuel injected from the in-cylinder injector 35 is the cylinder on the inner wall of the piston 24 or the cylinder 23. Considering that it is difficult to reach the liner, the operating time of the in-cylinder injector 35 is set to a longer t3 time, and the amount of fuel injected into the combustion chamber 25 is increased. By increasing the number, it is possible to compensate for the suppression of the fuel injection amount due to the operation at the top dead center side for t1 time and the operation at the bottom dead center side for t2 time.

  On the other hand, in the in-cylinder injection + intake pipe injection mode (NO in step 101, YES in step 103), as shown in FIG. 4, the intake pipe injection injector 36 is operated for t0 time in the exhaust stroke before the intake stroke period ( Step 104). In particular, the intake pipe injection injector 36 is operated at the beginning of the exhaust stroke period so that the fuel injected from the intake pipe injection injector 36 can shift to the intake stroke in a state where the air in the intake pipe 31 is sufficiently mixed.

  In the intake stroke period, as in the in-cylinder injection mode, the in-cylinder injector 35 is intermittently operated, and the fuel injection amount for each operation of the in-cylinder injector 35 is controlled according to the position of the piston 24. (Step 102).

  In this case, an appropriate amount of fuel commensurate with the running load of the vehicle is supplied to the combustion chamber 25 by the fuel injection by the intake pipe injector 36 and the fuel injection by the in-cylinder injector 35. In particular, the operation time of the in-cylinder injector 35 is set to the time t1 in the in-cylinder injection mode, the time t1, and the time t1x slightly shorter than the time t2 by the amount of fuel injection by the in-pipe injection injector 36. It can be reduced to t2x time between t3x. The relationship between t1x time, t3x, and t2x time is t1x <t2x <t3x.

  As described above, since the operation time of the in-cylinder injector 35 can be reduced to t1x time, t3x time, and t2x time, generation of particulates can be further suppressed than in the in-cylinder injection mode.

  In the intake pipe injection mode (NO in step 101, NO in step 103), the intake pipe injection injector 36 is operated for a predetermined time in the exhaust stroke before the intake stroke period (step 105). By the fuel injection by the intake pipe injection injector 36, an appropriate amount of fuel commensurate with the running load of the vehicle is supplied to the combustion chamber 25.

[Modification]
In the above embodiment, in the in-cylinder injection mode, the in-pipe injection injector 36 is operated three times during the intake period for t1 hours, t3, and t2 hours. However, as shown in FIG. For example, the operation may be performed in five steps.

  In this case, when the position of the piston 24 is slightly away from the top dead center, the in-cylinder injector 35 is operated in three short t11 times. The t11 time is shorter than the t1 time.

  Subsequently, when the position of the piston 24 is in a region approximately halfway between the top dead center and the bottom dead center, and the moving speed of the piston 24 becomes the fastest, the in-cylinder injector 35 is moved twice every t12 hours and t13 hours. Operate separately. The t13 time is shorter than the t3 time, and the t12 time is shorter than the t2 time. The relationship between t11 time, t13, and t12 time is t11 <t12 <t13.

  At the timing when the piston 24 approaches the bottom dead center, the in-cylinder injector 35 is not operated.

  As described above, when the piston 24 is located near the top dead center, the moving speed of the piston 24 is slow, and the fuel injected from the in-cylinder injector 35 can easily reach the cylinder liner on the inner wall of the piston 24 or the cylinder 23. In view of this, the in-cylinder injector 35 is operated a plurality of times for each short t11 time, and the amount of fuel injected into the combustion chamber 25 is suppressed to a small amount. Thereby, the adhesion amount of the fuel to the piston 24 and the cylinder liner can be suppressed. As a result, generation | occurrence | production of particulate matter, what is called a particulate, can be suppressed.

  When the piston 24 approaches bottom dead center, the in-cylinder injector 35 is not operated because the intake stroke period is at the end and the next compression stroke period is near. Thereby, it is possible to reliably prevent a problem that the fuel injected into the combustion chamber 25 shifts to the compression stroke without being sufficiently vaporized.

  When the piston 24 is in a region approximately between the top dead center and the bottom dead center, the moving speed of the piston 24 is the fastest, and the fuel injected from the in-cylinder injector 35 is the cylinder on the inner wall of the piston 24 or the cylinder 23. Considering that it is difficult to reach the liner, the operation time of the in-cylinder injector 35 is operated for longer t13 hours and t12 hours, so that the fuel injection amount into the combustion chamber 25 is increased. By making it larger, it is possible to compensate for the suppression of the fuel injection amount due to the three operations for t11 hours.

  In the in-cylinder injection + intake pipe injection mode, as shown in FIG. 6, the in-pipe injection injector 36 is operated for t0 time in the exhaust stroke before the intake stroke period, and the in-cylinder injector 35 is operated in the intake stroke period. First, it is operated three times for t11x time, and then is operated twice for t13 hours and t12 hours. The times t11x, t13x, and t12x are slightly shorter than the times t11, t13, and t12x, and have a relationship of t11x <t12x <t13x. Since the operation time of the in-cylinder injector 35 can be reduced to t11x time, t13x time, and t12x time, generation of particulates can be further suppressed than in the in-cylinder injection mode.

  Note that the number of operations of the in-cylinder injector 35 in the intake stroke period is not limited to three or five, and may be appropriately determined according to the characteristics of the in-cylinder injector 35, the volume of the combustion chamber 25, and the like. .

  In addition, the said embodiment and modification are shown as an example and are not intending limiting the range of invention. The novel embodiments and modifications can be implemented in various other forms, and various omissions, rewrites, and changes can be made without departing from the spirit of the invention. In these embodiments and modifications, the scope of the invention is included in the gist, and is included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Main body, 21 ... Cylinder block, 22 ... Cylinder block, 23 ... Cylinder, 24 ... Piston, 25 ... Combustion chamber, 31 ... Intake pipe, 35 ... In-cylinder injection injector, 36 ... Intake pipe injection injector 50 ... ECU (control unit), 100 ... crankshaft, 101 ... connecting rod

Claims (3)

A piston that reciprocates in a cylinder to form a variable volume combustion chamber in the cylinder;
An in-cylinder injector that directly injects fuel into the combustion chamber;
The in-cylinder injector is intermittently operated during an intake stroke period in which air is sucked into the combustion chamber by the forward movement of the piston, and the position of the piston is determined by the amount of fuel injection for each operation of the in-cylinder injector. Control means to increase when it is on the center side than when it is on the side,
An internal combustion engine comprising: The control means makes the operation time of the intermittent operation of the in-cylinder injector longer when the forward movement position of the piston is in the middle region than in the start end region and the end region.
The internal combustion engine according to claim 1. An intake pipe injection injector for injecting fuel into the intake pipe communicating with the combustion chamber;
The control means operates the intake pipe injection injector before the intake stroke period.
The internal combustion engine according to claim 1 or 2, characterized by the above.

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