JP4258396B2 - Premixed compression ignition internal combustion engine - Google Patents

Description

  The present invention relates to a premixed compression ignition internal combustion engine that performs premixed combustion by forming a premixed gas in a cylinder by a fuel injection valve that injects fuel into an intake port.

  In a compression ignition internal combustion engine (hereinafter, simply referred to as “internal combustion engine”), premixed combustion is performed for the purpose of suppressing exhausted NOx and white smoke. In this premixed combustion, fuel is generally injected into a cylinder at a time earlier than the top dead center of the compression stroke, thereby forming a uniform premixed gas in the combustion chamber. When this uniform premixed gas burns, the flame temperature is kept low, so that the generation of NOx is suppressed. In addition, since this premixed gas has a uniform mixture of fuel and air, the fuel will burn in the presence of a sufficient amount of oxygen, and therefore smoke will be generated due to combustion in the absence of oxygen. Is also suppressed.

  Here, in order to realize premixed combustion, a technique for controlling the fuel injection timing from an in-cylinder injection valve that injects fuel directly into a cylinder according to the engine load of the internal combustion engine is disclosed. For example, when the load is low, fuel is injected from the cylinder injection valve at a timing of 50 degrees before the compression stroke top dead center. When the load is high, the compression stroke top dead center is added in addition to the timing of 50 degrees before the compression stroke top dead center. By performing fuel injection at a nearby time, premixed combustion is enabled (see, for example, Patent Document 1).

In addition, in an internal combustion engine having an in-port injection valve capable of injecting fuel into an intake port in addition to an in-cylinder injection valve that directly injects fuel into the cylinder, fuel injection from the in-port injection valve is performed at low load. When the load is high, fuel injection is performed from the in-cylinder injection valve and the in-port injection valve, thereby enabling premixed combustion (see, for example, Patent Document 2). That is, as compared with the case where the premixed gas is formed by the fuel injection from the cylinder injection valve, the fuel injection is performed to the intake port by the in-port injection valve, thereby securing the time for forming the premixed gas, It is possible to suppress NOx generation and the like as much as possible.
JP 2000-179378 A JP-A-10-252512 JP-A-63-41661 Japanese Patent Laid-Open No. 5-126021 JP 2000-337226 A JP 2002-322969 A JP 2003-262175 A Japanese Patent Laid-Open No. 2000-27735

As described above, in an internal combustion engine having an in-port injection valve capable of injecting fuel into an intake port in addition to an in-cylinder injection valve that directly injects fuel into the cylinder, the fuel is injected from the in-port injection valve into the intake stroke. By performing injection, it is possible to form premixed gas in the cylinder and perform premixed combustion.

  However, since light oil used as engine fuel for internal combustion engines is less evaporable than gasoline, etc., the fuel introduced into the cylinder after being injected from the in-port injection valve does not form a premixed gas. In addition, it may adhere to the inner wall surface of the cylinder and cause dilution of the lubricating oil.

  In the present invention, in view of the above-described problems, when premixed combustion is performed in an internal combustion engine having an in-port injection valve capable of fuel injection in an intake port in addition to an in-cylinder injection valve that directly injects fuel into the cylinder. An object of the present invention is to more reliably suppress the fuel injected from the in-port injection valve from adhering to the inner wall surface of the cylinder.

  In order to solve the above-described problems, the present invention has an in-port injection valve and an in-cylinder injection valve. When premixed combustion is performed by fuel injection from the in-port injection valve, the injection is performed from the in-port injection valve. Attention was paid to the collision between the spray formed by the injected fuel and the spray formed by the fuel injected from the in-cylinder injection valve. When the former spray collides with the latter spray, the former spray, which is mainly premixed, is prevented from moving toward the cylinder inner wall surface, so that the fuel constituting the former spray adheres to the cylinder inner wall surface. It is because it becomes possible to suppress.

Therefore, the present invention includes an in-cylinder injection valve that injects fuel into a cylinder of an internal combustion engine, and an in-port injection valve that injects fuel into an intake port connected to the cylinder, and at least by the in-port injection valve In a premixed compression ignition internal combustion engine in which premixed gas is formed in the cylinder and premixed combustion is performed by performing fuel injection earlier than the time near the top dead center of the compression stroke, the in-cylinder injection valve and the port The relative arrangement with the internal injection valve is an arrangement in which the spray formed by the fuel injected from the in-port injection valve collides with the spray formed by the fuel injected from the in-cylinder injection valve. , performs premixed combustion injected into said intake port from the port injection valve during the intake stroke, with respect to the premixing combustion injection, fuel produced in the cylinder by injecting premix combustion With a predetermined delay time to collision spray of fuel from the spray cylinder injection valve performs cylinder preinjection from said cylinder injection valve into the cylinder.

  In the premixed compression ignition internal combustion engine, the fuel injection from the in-port injection valve is performed during the intake stroke as described above, so that the injected fuel forms a premixed gas, thereby realizing premixed combustion. The The fuel injection from the cylinder injection valve is performed when fuel corresponding to the engine load cannot be sufficiently injected by the fuel injection from the port injection valve. In particular, when premixed combustion is performed, the premixed gas is ignited at a timing earlier than the target ignition timing, generally near the top dead center of the compression stroke. When the fuel injection amount is limited, the remaining fuel is injected from the in-cylinder injection valve.

  Here, the in-cylinder injection valve and the in-port injection valve are arranged at relative positions where the sprays formed by the respective injection valves can collide with each other. That is, when the spray formed by the fuel injected from the in-port injection valve is introduced into the cylinder, the spray overlaps with the spray formed by the fuel injected into the cylinder by the cylinder injection valve. Therefore, an in-cylinder injection valve and an in-port injection valve are provided. In particular, an in-cylinder injection valve and an in-port injection valve are provided in consideration of the direction of the fuel injection hole in each injection valve.

In the premixed compression ignition internal combustion engine configured as described above, the premixed fuel is formed by performing the premixed combustion injection from the intake valve, thereby realizing the premixed combustion. Here, when the premixed combustion injection is performed, the in-cylinder preliminary injection is performed from the in-cylinder injection valve after a predetermined delay time has elapsed from the injection, whereby the premixed combustion injection and the in-cylinder preliminary injection are performed. The spray collides with the inside of the cylinder. As a result, the spray from the premixed combustion injection is prevented from moving toward the cylinder from the intake port, and further toward the inner wall surface of the cylinder, by the spray due to the preliminary injection in the cylinder. As a result, it is possible to suppress the fuel constituting the spray by the premixed combustion injection from adhering to the cylinder inner wall surface.

  Accordingly, the predetermined delay time is a time for adjusting the timing of the in-cylinder preliminary injection so that the spray collides with the spray by the in-cylinder preliminary injection when the spray by the premixed combustion injection is introduced into the cylinder. It is. Therefore, the predetermined delay time may be determined in consideration of the time until the fuel flows through the intake port and reaches the cylinder.

  The amount of fuel injected by the in-cylinder pre-injection is preferably as small as possible on condition that the spray fuel adhering to the cylinder inner wall surface by the pre-mixed combustion injection can be suppressed. When the amount of fuel injected by in-cylinder pre-injection increases, the adhesion of fuel sprayed by premix combustion injection to the cylinder inner wall surface is suppressed, but conversely, the fuel sprayed by in-cylinder pre-injection is injected into the cylinder inner wall surface. It is because there is a possibility that it may adhere to.

  Here, in the premixed compression ignition internal combustion engine, the in-port injection valve has two types of injection holes having different diameters of fuel injection holes, and a lift amount of the intake valve provided in the intake port is a predetermined lift. When the amount is lower than the amount, fuel is injected from a small nozzle hole with a small fuel nozzle diameter, and when the lift amount of the intake valve is equal to or greater than a predetermined lift amount, fuel is injected at least from a large nozzle hole with a large fuel hole diameter Thus, premixed combustion injection may be performed, and the in-cylinder preliminary injection may be performed with the predetermined delay time with respect to the fuel injection from the large injection hole in the premixed fuel injection.

  In the in-port injection valve configured as described above, first, when the lift amount of the intake valve is low, which is smaller than the predetermined lift amount, the substantial flow path area in the intake port is relatively small. Therefore, in this case, fuel is injected from the small nozzle hole. Since the injected fuel is atomized more than the fuel injected from the large injection hole, the evaporability of the fuel is improved, and as a result, the injected fuel can be prevented from adhering to the intake port. However, since the diameter of the fuel injection hole is small, the fuel injection rate is small. Therefore, when the lift amount of the intake valve is higher than a predetermined lift amount, the substantial flow passage area in the intake port becomes relatively large. The fuel injection rate is improved, but the required amount of fuel is injected within the required time.

  Here, in the premixed compression ignition internal combustion engine having the in-port injection valve, when the fuel injection is performed from the small injection hole for the premixed combustion, the injected fuel is atomized and relatively evaporated. Since the fuel is a good fuel and the fuel injection rate is relatively low, there is little possibility that the injected fuel adheres to the inner wall surface of the cylinder when the fuel is introduced into the cylinder. On the other hand, when fuel is injected from the large nozzle hole, the fuel particle size is large and the evaporability of the injected fuel is reduced. Further, since the fuel injection rate is relatively high, the injected fuel is applied to the inner wall surface of the cylinder. There is a risk of adhesion. Therefore, in the premixed combustion injection, the in-cylinder preliminary injection is performed with the predetermined delay time based on the fuel injection from the large injection hole. As a result, in the premixed combustion injection, the fuel spray injected from the large injection hole collides with the spray generated by the in-cylinder preliminary injection, thereby preventing the fuel from adhering to the cylinder inner wall surface. obtain.

  Here, in the premixed compression ignition internal combustion engine described above, as the engine load increases, the fuel injection amount by the premixed combustion injection is increased in a range where pre-ignition does not occur. At the same time, there is a high possibility that the injected fuel adheres to the cylinder inner wall surface. Therefore, the fuel injection amount by the in-cylinder preliminary injection may be increased as the fuel injection amount by the premixed combustion injection increases. By doing in this way, spray can collide with each other more reliably and adhesion of fuel to the cylinder inner wall surface can be suppressed.

  In addition, in the in-cylinder injection valve, in addition to the above-described in-cylinder preliminary injection, when performing in-cylinder main injection into the cylinder at a timing near the compression stroke top dead center, the fuel injection amount in the premixed combustion injection is large. Accordingly, the ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection may be increased and corrected. As described above, by increasing the fuel injection amount in the in-cylinder preliminary injection, it is possible to more reliably suppress the adhesion of fuel to the cylinder inner wall surface due to the increase in the fuel injection amount in the premixed combustion injection.

  Similarly, in the in-cylinder injection valve, in addition to the above-described in-cylinder preliminary injection, when performing in-cylinder main injection into the cylinder at a timing near the compression stroke top dead center, as the intake flow rate in the intake port increases, The ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection may be increased and corrected. When the intake air flow rate at the intake port increases, the momentum of the fuel injected by the premixed combustion injection increases, and the risk of the fuel adhering to the cylinder inner wall surface increases. Thus, in such a case, by increasing the fuel injection amount in the in-cylinder preliminary injection, it is possible to more reliably suppress the fuel from adhering to the cylinder inner wall surface due to the increase in the fuel injection amount in the premixed combustion injection.

  The in-cylinder injection valve injects fuel into the cylinder, and the in-cylinder preliminary injection is performed after a predetermined delay time from the premixed combustion injection in the intake stroke. When increasing the amount, if the increased amount of fuel is injected, the fuel may adhere to the inner wall surface of the cylinder. Therefore, it is preferable that the fuel injection amount in the in-cylinder pre-injection is corrected in the above-described manner so that the fuel injected in the in-cylinder preliminary injection does not adhere to the inner wall surface of the cylinder.

  On the other hand, in the in-cylinder injection valve, in addition to the above-described in-cylinder preliminary injection, when performing in-cylinder main injection into the cylinder at a timing near the compression stroke top dead center, as the intake air temperature in the intake port increases, A ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection may be corrected to decrease.

  When the temperature of the intake air at the intake port increases, the evaporability of the fuel injected by the premixed combustion injection is improved, and the momentum of the fuel toward the cylinder inner wall surface is reduced. That is, the fuel diffuses more widely in the cylinder. In such a case, the fuel injected by the premixed combustion injection is less likely to adhere to the inner wall surface of the cylinder. Therefore, by reducing the fuel injection amount in the in-cylinder preliminary injection, the cylinder of fuel by the in-cylinder preliminary injection is reduced. Adhesion to the inner wall surface can be more reliably suppressed.

  Here, in the premixed compression ignition internal combustion engine described above, the predetermined delay time for determining the start timing of the in-cylinder preliminary injection may be set shorter as the intake flow rate flowing through the intake port increases. That is, when the intake flow rate flowing through the intake port increases, the time from when the fuel injected by the premixed combustion injection is injected until it reaches the cylinder is shortened. Therefore, by setting a predetermined delay time according to the shortening of the time, the collision between the spray by the premixed combustion injection and the spray by the in-cylinder pre-injection can be generated more reliably, and thus the cylinder inner wall surface of the fuel Adhesion to can be suppressed.

  In the present invention, in the case of performing premixed combustion in an internal combustion engine having an in-port injection valve capable of fuel injection in an intake port in addition to an in-cylinder injection valve that directly injects fuel into the cylinder, the in-port injection valve It is possible to more reliably suppress the fuel injected from the fuel from adhering to the cylinder inner wall surface.

  Here, the form of the premixed compression ignition internal combustion engine which concerns on this invention is demonstrated based on drawing.

  FIG. 1 is a block diagram showing a schematic configuration of a compression ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 and its control system to which the present invention is applied. The internal combustion engine 1 includes an in-cylinder injection valve 3 that can inject fuel directly into the cylinder 2. From the cylinder injection valve 3, fuel is injected radially into the cylinder. In the cylinder 2, the piston 4 reciprocates. The internal combustion engine 1 has an intake passage connected to a combustion chamber via an intake port 7. Similarly, an exhaust passage is connected to the combustion chamber through the exhaust port 8 in the internal combustion engine 1. Here, an intake valve 5 is provided at the boundary between the intake port 7 and the combustion chamber, and an exhaust valve 6 is provided at the boundary between the exhaust port 8 and the combustion chamber. An air flow meter 13 that detects the flow rate of the intake air that flows through the intake passage and flows into the intake port 7 is provided in the intake passage on the upstream side of the intake port 7.

  In addition, the intake port 7 is provided with an in-port injection valve 9 capable of injecting fuel into the intake port 7. In the in-port injection valve 9, fuel is injected into the intake port 7 from a plurality of injection holes having the same diameter. The fuel supplied to the cylinder injection valve 3 and the port injection valve 9 is the same fuel supplied from the same fuel tank (not shown).

  Further, the internal combustion engine 1 is provided with an exhaust gas recirculation passage 11 that leads from the exhaust port 8 to the intake port 7. A part of the exhaust gas flowing through the exhaust port 8 is recirculated to the intake port 7 as EGR gas through the exhaust gas recirculation passage 11. The exhaust gas recirculation passage 11 is provided with an EGR cooler 12 that cools the EGR gas flowing through the passage, and an EGR valve 10 that adjusts the flow rate of the EGR gas flowing through the exhaust gas recirculation passage 11 is provided downstream thereof. It has been.

  Here, the internal combustion engine 1 is provided with an electronic control unit (hereinafter referred to as “ECU”) 20 for controlling the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, and the like for storing various control routines and maps to be described later, and the operating conditions of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. The unit to control. Here, the in-cylinder injection valve 3, the in-port injection valve 9, and the EGR valve 10 are opened and closed by a control signal from the ECU 20.

  Further, the crank position sensor 15 and the accelerator opening sensor 16 are electrically connected to the ECU 20. Accordingly, the ECU 20 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1 and calculates the engine rotational speed Ne or the like of the internal combustion engine 1, or receives a signal corresponding to the accelerator opening and requests the internal combustion engine 1 The engine load Tq and the like to be calculated are calculated. An intake air temperature sensor 14 for detecting the temperature Tin of the intake air flowing through the intake port 7 and an air flow meter 13 are electrically connected to the ECU 20.

  Next, details of the arrangement of the cylinder injection valve 3 and the port injection valve 9 will be described with reference to FIG. FIG. 2 is a view of the vicinity of the cylinder 2 of the internal combustion engine 1 shown in FIG. 1, and the illustration of the intake valve 5 and the exhaust valve 6 is omitted for the sake of simplicity of explanation. A spray 9 a is formed by the fuel injected from the in-port injection valve 9, and a spray 3 a is formed by the fuel injected from the in-cylinder injection valve 3.

Here, the relative positional relationship between the in-cylinder injection valve 3 and the in-port injection valve 9 is a positional relationship in which the spray 3a and the spray 9a can collide when fuel is injected from each other at a predetermined injection timing. It has become. In other words, the fuel injection direction from the in-cylinder injection valve 3 that injects fuel radially into the cylinder 2 spatially overlaps with the fuel injection direction from the in-port injection valve 9 in the cylinder 2.

  In the internal combustion engine 1 configured as described above, fuel is injected from the in-port injection valve 9 in the intake stroke in accordance with the operating state determined from the engine load Tq and the engine speed Ne required for the internal combustion engine. Thus, a premixed gas is formed in the cylinder 2 and premixed combustion is performed. The fuel injected from the in-port injection valve 9 in the intake stroke is introduced into the cylinder 2 together with the intake air through the intake port 7 along with the opening of the intake valve 5. Thereafter, the fuel diffuses in the cylinder 2 to become a premixed gas.

  By injecting the fuel forming the premixed gas from the in-port injection valve 9 into the intake port 7, the fuel is directly injected into the cylinder 2 to form the premixed gas on the inner wall surface of the cylinder 2. There is a low risk that the fuel will adhere and dilute the lubricating oil. However, light oil used as a fuel for the internal combustion engine 1 which is a compression ignition internal combustion engine is less evaporable than gasoline. Therefore, even when fuel is injected from the in-port injection valve 9 to form the premixed gas, there is a possibility that the fuel introduced into the cylinder 2 does not evaporate and adheres to the inner wall surface in the cylinder 2.

  Therefore, when fuel is injected from the in-port injection valve 9 and when the resulting spray 9 a is introduced into the cylinder 2, the spray 9 a collides with the spray 3 a by the in-cylinder injection valve 3, thereby causing the spray 9 a to flow. It is possible to prevent the fuel to be formed from moving toward the inner wall surface of the cylinder 2 and suppress the fuel from adhering to the inner wall surface.

  Here, based on FIG. 3, the injection timing of the in-cylinder injection valve 3 for the spray 9a to collide with the spray 3a will be described. The horizontal axis of FIG. 3 represents the crank angle of the internal combustion engine 1, and TDC in the figure means the top dead center of the compression stroke. Further, −360CA and −180CA mean crank angles 360 degrees and 180 degrees before the crank angle with respect to TDC. The upper part of FIG. 3 is a diagram showing the timing of fuel injection (INJ1) into the intake port 7 by the in-port injection valve 9, and the lower part of FIG. It is a figure showing the time of fuel injection (INJ2, INJ3).

  The fuel injection in the in-port injection valve 9 is performed as injection INJ1 (hereinafter also referred to as “premixed combustion injection”). The injection INJ1 is performed in the intake stroke (a period from −360 CA to −180 CA), and the injection amount is Qp, and premixed gas is mainly formed by the injection.

  The fuel injection in the in-cylinder injection valve 3 is performed as injections INJ2 (hereinafter also referred to as “in-cylinder preliminary injection”) and INJ3 (hereinafter also referred to as “in-cylinder main injection”). The injection amount by the injection INJ2 is Qpl, and the injection amount by the injection INJ3 is Qm. Since the spray formed by the injected fuel in the injection INJ2 collides with the spray formed by the injected fuel in the injection INJ1, the injection INJ2 is performed with a predetermined delay time τd after the injection INJ1 is started. . The predetermined delay time τd is determined based on whether or not the intake valve 5 is open, or the time required for the fuel injected from the in-port injection valve 9 to reach the cylinder 2 together with the intake air. .

  Thus, by performing the injection INJ2 with the predetermined delay time τd with respect to the injection INJ1, the fuel injected from the in-port injection valve 9 that mainly forms the premixed gas is injected from the in-cylinder injection valve 3. It is possible to prevent the former fuel from adhering to the inner wall surface of the cylinder 2 by causing the fuel to collide.

Here, since the injection INJ2 is an injection performed in the intake stroke and is performed with a predetermined delay time τd with respect to the injection INJ1, if the injection amount Qpl of the injection INJ2 becomes excessively large, the injection by the injection INJ2 There is a possibility that the fuel adheres to the inner wall surface of the cylinder 2. Therefore, the injection amount Qpl of the injection INJ2 is made as small as possible on condition that the injection INJ1 can suppress the adhesion of the injected fuel to the inner wall surface of the cylinder 2.

  When it is difficult to supply the fuel required to meet the engine load of the internal combustion engine 1 by the injection INJ1 and the injection INJ2, the remaining fuel is injected at the injection INJ3 (injection amount Qm). Since the injection INJ3 is performed at a time near the TDC, the fuel injected by the injection INJ3 does not adhere to the inner wall surface of the cylinder 2 and is burned together with the premixed air.

  Next, fuel injection control that is repeatedly executed when premixed combustion is performed in the internal combustion engine 1 will be described in detail with reference to FIG. The injection timings of the in-cylinder injection valve 3 and the in-port injection valve 9 when the fuel injection control shown in FIG. 4 is performed are generally as shown in FIG.

  In S101, the engine load Tq required for the internal combustion engine 1 is calculated based on the signal from the accelerator opening sensor 16, and the total fuel injection amount Qtotal corresponding to the engine load Tq is calculated. When the process of S101 ends, the process proceeds to S102.

  In S102, the premixed combustion injection amount (fuel injection amount in the injection INJ1 shown in FIG. 3) Qp, which is the fuel injection amount from the in-port injection valve 9, is calculated. In calculating the premixed combustion injection amount Qp, it is based on the engine speed Ne and the engine load Tq of the internal combustion engine 1 in consideration of forming a uniform premixed gas in the cylinder 2 and avoiding premature ignition. Calculated. When the process of S102 ends, the process proceeds to S103.

  In S103, a spray that collides with the spray formed by the fuel, which is necessary and sufficient to suppress the fuel of the premixed combustion injection amount Qp calculated in S102 from adhering to the inner wall surface of the cylinder 2, is formed. Therefore, the fuel injection amount from the in-cylinder injection valve 3, that is, the in-cylinder preliminary injection amount Qpl which is the fuel injection amount in the injection INJ2 shown in FIG. Specifically, in order to suppress the fuel of the premixed combustion injection amount Qp from adhering to the inner wall surface of the cylinder 2, the in-cylinder preliminary injection increases as the premixed combustion injection amount Qp calculated in S102 increases. The quantity Qpl is increased and set.

  Here, in the in-cylinder preliminary injection, fuel is injected by the in-cylinder injection valve 3, so that the fuel tends to adhere to the inner wall surface of the cylinder 2. When the in-cylinder preliminary injection amount Qpl is increased and exceeds the reference amount Qplmax, the fuel is prevented from adhering to the inner wall surface of the cylinder 2 by colliding with the fuel by the premixed combustion injection. There is a possibility that the fuel itself by the internal preliminary injection may adhere to the inner wall surface of the cylinder 2. Therefore, the value of the in-cylinder preliminary injection amount Qpl is set with the upper limit being Qplmax. When the process of S103 ends, the process proceeds to S104.

  In S104, an in-cylinder main injection amount Qm that is a fuel injection amount in the injection INJ3 shown in FIG. 3 is calculated. That is, the in-cylinder main injection Qm is a value obtained by subtracting the premixed combustion injection amount Qp calculated in S102 and the in-cylinder preliminary injection amount Qpl calculated in S103 from the total injection amount Qtotal calculated in S101. When the process of S104 ends, the process proceeds to S105.

In S105, the in-cylinder preliminary injection amount Qpl calculated in S103 and the in-cylinder main injection amount Qm calculated in S104 are corrected based on the state of the intake air flowing through the intake port 7. This is because, depending on the state of the intake air flowing through the intake port 7, the degree of adhesion of the injected fuel by the premixed combustion injection to the inner wall surface of the cylinder 2 is different, and the injected fuel by the in-cylinder preliminary injection is the inner wall surface of the cylinder 2. This is because it is preferable to make the injection amount as appropriate as possible.

  Specifically, first, the in-cylinder preliminary injection amount Qpl and the in-cylinder main injection amount Qm are corrected based on the flow rate of the intake air flowing through the intake port 7. That is, the momentum of the fuel injected from the in-port injection valve 9 increases as the flow rate of the intake air increases, so that there is a high possibility that the fuel adheres to the inner wall surface of the cylinder 2. Therefore, the in-cylinder preliminary injection amount Qpl and the in-cylinder main injection amount Qm are corrected according to the following equations (1) and (2).

In-cylinder preliminary injection amount Qpl = (calculated value in S103) × (1 + coefficient B) (Equation 1)
In-cylinder main injection amount Qm = Qtotal−Qp− (Qpl after correction in Equation 1) (Equation 2)
Here, the coefficient B is a coefficient that increases as the flow rate of the intake air flowing through the intake port 7 calculated based on the signal from the air flow meter 13 increases. The coefficient B is obtained by accessing the map showing the relationship between the intake air flow rate stored in the ECU 20 and the coefficient B using the intake air flow rate as a parameter.

  Based on the above formula, the in-cylinder preliminary injection amount Qpl is increased and corrected, and the in-cylinder main injection amount Qm is decreased and corrected as the intake air flow rate increases. That is, the ratio of the in-cylinder preliminary injection amount Qpl to the in-cylinder main injection amount Qm is corrected to be increased. Thereby, the fuel injection amount from the in-cylinder injection valve 3 for colliding with the spray from the in-port injection valve 9 is increased, and the injected fuel from the in-port injection valve 9 whose momentum has increased is the inner wall surface of the cylinder 2. It is possible to more reliably suppress adhesion to the surface.

  Here, when increasing the in-cylinder preliminary injection Qpl as described above, the upper limit value after the increase is made not to exceed the above-described Qplmax. Thereby, it becomes possible to suppress the fuel adhesion to the inner wall surface of the cylinder 2 due to the in-cylinder preliminary injection.

  Next, based on the temperature of the intake air flowing through the intake port 7, the in-cylinder preliminary injection amount Qpl and the in-cylinder main injection amount Qm are corrected. That is, as the temperature of the intake air rises, the evaporation of the fuel injected from the in-port injection valve 9 is promoted and its momentum decreases, so that the risk of the fuel adhering to the inner wall surface of the cylinder 2 is reduced. For example, when EGR gas is recirculated to the intake port 7 via the exhaust gas recirculation passage 11, the intake air temperature becomes relatively high. Therefore, the in-cylinder preliminary injection amount Qpl and the in-cylinder main injection amount Qm are corrected according to the following equations (3) and (4).

In-cylinder preliminary injection amount Qpl = (calculated value in S103) × (1−coefficient C) (Equation 3)
In-cylinder main injection amount Qm = Qtotal−Qp− (Qpl after correction in Expression 3) (Expression 4)
Here, the coefficient C is a coefficient that increases as the temperature of the intake air flowing through the intake port 7 calculated based on the signal from the intake air temperature sensor 14 increases. The coefficient C is obtained by accessing a map showing the relationship between the intake air temperature and the coefficient C stored in the ECU 20 using the intake air temperature as a parameter.

  Based on the above equation, the in-cylinder preliminary injection amount Qpl is corrected to decrease as the intake air temperature increases, and the in-cylinder main injection amount Qm is corrected to increase. That is, the ratio of the in-cylinder preliminary injection amount Qpl to the in-cylinder main injection amount Qm is corrected to decrease. Thereby, the fuel injection amount from the in-cylinder injection valve 3 for colliding with the spray from the in-port injection valve 9 is reduced, and the amount of fuel injected from the in-cylinder injection valve 3 by the in-cylinder preliminary injection is set to an appropriate amount. In addition, it is possible to more reliably suppress the fuel from adhering to the inner wall surface of the cylinder 2.

  When the process of S105 ends, the process proceeds to S106.

In S106, a predetermined delay time τd for determining the injection timing for performing the in-cylinder preliminary injection is calculated according to the flow rate of the intake air flowing through the intake port 7. That is, the predetermined delay time τd is determined in consideration of the fact that as the intake flow rate increases, the time for the fuel injected from the in-port injection valve 9 by the premixed combustion injection to reach the cylinder 2 is shortened. The Specifically, the predetermined delay time τd is calculated according to the following equation (5).

Predetermined delay time τd = (base value) −coefficient D (Expression 5)
Here, the coefficient D is a coefficient that increases as the flow rate of the intake air flowing through the intake port 7 calculated based on the signal from the air flow meter 13 increases. The coefficient D is obtained by accessing a map showing the relationship between the intake air temperature and the coefficient D stored in the ECU 20 using the intake air temperature as a parameter. The base value is stored in advance in the ECU 20.

  Based on the above formula, the predetermined delay time τd is shortened as the intake flow rate increases. Thereby, the fuel injection timing from the in-cylinder injection valve 3 for making it collide with the spray from the in-port injection valve 9 can be made more appropriate, and the collision of the spray can be generated more reliably. As a result, it is possible to more reliably suppress the fuel injected from the in-port injection valve 9 by the premixed combustion injection from adhering to the inner wall surface of the cylinder 2. When the process of S106 ends, the process proceeds to S107.

  In S107, the ECU 20 calculates the corrected premixed combustion injection amount Qp, the in-cylinder preliminary injection amount Qpl, the in-cylinder main injection amount Qm, and the predetermined delay time τd as described above, and the ECU 20 An injection command is issued to the injection valve 3 to perform fuel injection. The injection start timing in the in-port injection valve 9 is in the intake stroke as shown in FIG. After the process of S107, this control ends.

  According to this control, during the premix combustion of the internal combustion engine 1, the premixed fuel is formed in the cylinder 2 by performing the premixed combustion injection from the in-port injection valve 3 during the intake stroke. At that time, the fuel injected by the premixed combustion injection collides with the fuel injected by the in-cylinder preliminary injection, so that the fuel can be prevented from adhering to the inner wall surface of the cylinder 2.

  Next, as a second embodiment of the present invention, fuel injection control at the time of premix combustion when the in-port injection valve 9 of the internal combustion engine 1 shown in FIG. 1 has two types of injection holes with different diameters. In particular, control of the fuel injection timing will be described. The in-port injection valve according to the present embodiment is distinguished from the in-port injection valve 9 in the first embodiment as an in-port injection valve 90.

  FIG. 5 shows a detailed structure around the injection hole of the in-port injection valve 90 according to the present embodiment. The outer shell 95 of the in-port injection valve 90 is provided with a small nozzle hole 93 having a small nozzle hole diameter and a large nozzle hole 94 having a large nozzle hole diameter. Here, the large injection hole 94 is provided in a portion near the tip of the outer shell 95, while the small injection hole 93 is provided in a portion far from the tip of the outer shell 95 compared to the large injection hole 94. Yes. Then, fuel is injected from the in-port injection valve 90 through the small injection hole 93 and the large injection hole 94.

Here, the fuel injection from the in-port injection valve 90 is provided inside the outer shell 95 and can be moved in the longitudinal direction of the in-port injection valve 90 by two needle valves 91 and 92 (hereinafter referred to as “needle valve 91” The first needle valve 91 "and the needle valve 92 are controlled by a" second needle valve 92 "). Specifically, as shown in FIG. 5A, first, when the in-port injection valve 90 is in the closed state, that is, the first needle valve 91 and the second needle valve 92 are in the initial state, Is in a state in contact with the inner wall surface of the outer shell 95, the fuel does not reach the small injection hole 93 and the large injection hole 94, so the fuel is not injected. In addition, what is represented by the arrow in FIG. 5 means the flow of fuel.

  Next, as shown in FIG. 5 (b), the first needle valve 91 moves and the contact state with the inner wall surface of the outer shell 95 is eliminated, but the contact between the second needle valve 92 and the inner wall surface is eliminated. When the state is maintained, the fuel does not reach the large injection hole 94 but is injected only from the small injection hole 93. In addition, as shown in FIG.5 (b), the fuel injection from only the small nozzle hole 93 is called small nozzle injection.

  Next, as shown in FIG. 5C, the first needle valve 91 and the second needle valve 92 are further moved from the state of FIG. When the contact state between both valves and the inner wall surface of the outer shell 95 is eliminated, the fuel reaches the large injection hole 94 and the fuel is injected from the small injection hole 93 and the large injection hole 94. In addition, as shown in FIG.5 (c), the fuel injection from the small injection hole 93 and the large injection hole 94 is called large injection hole injection.

  In the in-port injection valve 90 configured as described above, as shown in FIG. 6, when the lift amount of the intake valve 5 is 50% of the maximum amount as a boundary and the lift amount is less than 50%, the small injection is performed. Hole injection is performed, and at the time of high lift where the lift amount is 50% or more, large nozzle injection is performed. In the small injection hole injection, since the fuel is injected from the small injection hole 93, more atomized fuel is injected, thereby promoting the evaporation of the fuel. Therefore, adhesion to the intake port 7 is suppressed. On the other hand, since the diameter of the small injection hole 93 is small, the injection rate of the small injection hole is low. Therefore, when the intake valve 5 is in a high lift state and the substantial flow passage area in the intake port 7 is increased, the large injection hole injection is performed, whereby the fuel injection with a high injection rate from the large injection hole 94 is performed.

  Here, in the internal combustion engine 1, when premixed combustion is performed by injecting from the in-port injection valve 90 in the intake stroke, the fuel injected by the small injection hole injection from the in-port injection valve 90 is further atomized. Therefore, even if it is introduced into the cylinder 2 in the intake stroke, it is less likely to diffuse into the cylinder 2 and adhere to the inner wall surface of the cylinder 2. On the other hand, the fuel injected from the in-port injection valve 90 by the large injection hole injection, in particular, the fuel injected from the large injection hole 94 has a larger particle diameter than the fuel injected from the small injection hole 93, and therefore evaporates. The fuel is likely to adhere to the inner wall surface of the cylinder 2. Therefore, by controlling the injection timing of the in-cylinder injection valve 3 as shown in FIG. 7, it is possible to suppress the adhesion of fuel to the inner wall surface.

  FIG. 7 is a diagram illustrating the injection timing of the in-cylinder injection valve 3 for causing the spray from the in-port injection valve 90 to collide with the spray from the in-cylinder injection valve 3 as in FIG. 3. The horizontal axis in FIG. 7 is the same as in FIG. The upper part of FIG. 7 is a diagram showing the timing of small injection holes (INJ4, INJ5) when fuel is injected into the intake port 7 by the in-port injection valve 90 and the intake valve 5 is low lifted. The middle stage shows fuel injection into the intake port 7 by the in-port injection valve 90 and shows the timing of the large injection hole injection (INJ6) when the intake valve 5 is in a high lift, and the lower stage is the same as FIG. FIG. 5 is a diagram showing the timing of fuel injection (INJ2, INJ3) into the cylinder 2 by the in-cylinder injection valve 3. That is, for the sake of explanation, the upper and middle stages of FIG. 7 distinguish the fuel injection from the same in-port injection valve 90 into small injection holes and large injection holes according to the lift amount of the intake valve 5. It is what is written.

  Here, fuel injection is performed from the in-port injection valve 90 in the intake stroke, whereby premixed combustion is performed in the internal combustion engine 1. As described above, the small injection hole injection (fuel in the injection INJ4 or INJ5) when the intake valve 5 is in the low lift state is less likely to adhere to the inner wall surface in the cylinder 2, while the intake valve The large injection hole injection (fuel in the injection INJ6) when 5 is in the high lift state is highly likely to adhere to the inner wall surface in the cylinder 2.

Therefore, the aforementioned predetermined delay time τd for determining the in-cylinder preliminary injection (INJ2) by the in-cylinder injection valve 3 for suppressing the adhesion of the fuel to the inner wall surface of the cylinder 2 is the time when the injection INJ6 is started, That is, the time when the large injection hole injection is started when the intake valve 5 is in the high lift state is used as a reference. The fuel injection amount Qpl in the in-cylinder preliminary injection (INJ2) is determined according to the fuel injection amount in INJ6 at the time of the large injection hole injection. Accordingly, the Qpl is set to increase as the fuel injection amount in the injection INJ6 increases. At this time, Qpl should not exceed Qplmax described above.

  It is also possible to correct the fuel injection amount Qpl in the in-cylinder preliminary injection INJ2 and the fuel injection amount Qm in the in-cylinder main injection INJ3 in the process S105 during the fuel injection control shown in FIG.

  Thus, by performing the in-cylinder preliminary injection INJ2 with a predetermined delay time τd with respect to the large injection hole injection INJ6, the fuel injected from the in-port injection valve 90 that mainly forms the premixed gas is injected into the cylinder. By causing the fuel injected from the injection valve 3 to collide, it is possible to suppress the fuel from adhering to the inner wall surface of the cylinder 2.

1 is a diagram illustrating a schematic configuration of a premixed compression ignition internal combustion engine according to an embodiment of the present invention. FIG. 2 is a view in the vicinity of a cylinder 2 of the internal combustion engine shown in FIG. 1. In the premixed compression ignition internal combustion engine which concerns on 1st Example of this invention, it is a figure showing fuel injection timing. 3 is a flowchart relating to fuel injection control in the premixed compression ignition internal combustion engine according to the first embodiment of the present invention. It is a figure which shows the detailed structure of the injection valve in a port in the premixing compression ignition internal combustion engine which concerns on the 2nd Example of this invention. It is a figure showing transition of the lift amount of an intake valve in the premixed compression ignition internal combustion engine which concerns on the 2nd Example of this invention. In the premixed compression ignition internal combustion engine which concerns on 2nd Example of this invention, it is a figure showing fuel injection timing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Internal combustion engine 2 .... Cylinder 3 .... In-cylinder injection valve 4 .... Piston 5 .... Intake valve 6 .... Exhaust valve 7 .... Intake port 8・ ・ ・ ・ Exhaust port 9 ・ ・ ・ ・ Injection valve 13 ・ ・ ・ ・ Air flow meter 14 ・ ・ ・ ・ Intake temperature sensor 15 ・ ・ ・ ・ Crank position sensor 16 ・ ・ ・ ・ Accelerator opening sensor 20 ..ECU
90... In-port injection valve 91... First needle valve 92... Second needle valve 93.

Claims (7)

An in-cylinder injection valve for injecting fuel into the cylinder of the internal combustion engine;
An in-port injection valve for injecting fuel into an intake port connected to the cylinder,
In the premixed compression ignition internal combustion engine that forms premixed gas in the cylinder and performs premixed combustion by performing fuel injection at least earlier than the timing near the top dead center of the compression stroke by the in-port injection valve,
The relative arrangement of the in-cylinder injection valve and the in-port injection valve is such that the spray formed by the fuel injected from the in-port injection valve is formed by the fuel injected from the in-cylinder injection valve. An arrangement that collides with the spray,
During the intake stroke, premixed combustion injection is performed from the in-port injection valve into the intake port, and fuel spray generated in the cylinder by the premixed combustion injection is applied to the premixed combustion injection. A premixed compression ignition internal combustion engine that performs in-cylinder preliminary injection from the in-cylinder injection valve into the cylinder with a predetermined delay time for causing fuel spray from the in-cylinder injection valve to collide .
The in-port injection valve has two types of injection holes with different diameters of the fuel injection holes, and the diameter of the fuel injection holes is small when the lift amount of the intake valve provided in the intake port is lower than a predetermined lift amount. When fuel is injected from the small injection holes, and the lift amount of the intake valve is equal to or greater than a predetermined lift amount, at least fuel injection is performed from the large injection holes having a large diameter of the fuel injection holes, and premixed combustion injection is performed.
2. The premixed compression ignition internal combustion engine according to claim 1, wherein the in-cylinder preliminary injection is performed with the predetermined delay time with respect to fuel injection from the large injection hole in the premixed fuel injection. In fuel injection from the in-cylinder injection valve, in addition to the in-cylinder preliminary injection, in-cylinder main injection into the cylinder at a time near the compression stroke top dead center is performed,
The ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection is increased and corrected as the fuel injection amount in the premixed combustion injection increases. Item 3. A premixed compression ignition internal combustion engine according to Item 2. In fuel injection from the in-cylinder injection valve, in addition to the in-cylinder preliminary injection, in-cylinder main injection into the cylinder at a time near the compression stroke top dead center is performed,
The ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection is increased and corrected as the intake air flow rate in the intake port increases. Premixed compression ignition internal combustion engine. 5. The fuel injection amount in the in-cylinder preliminary injection is corrected to be increased within a range in which the fuel injected in the in-cylinder preliminary injection does not adhere to the inner wall surface of the cylinder. Premixed compression ignition internal combustion engine. In fuel injection from the in-cylinder injection valve, in addition to the in-cylinder preliminary injection, in-cylinder main injection into the cylinder at a time near the compression stroke top dead center is performed,
The ratio of the fuel injection amount in the in-cylinder preliminary injection to the fuel injection amount in the in-cylinder main injection is decreased and corrected as the intake air temperature at the intake port becomes higher. Premixed compression ignition internal combustion engine. The premixed compression ignition internal combustion engine according to any one of claims 1 to 6, wherein the predetermined delay time is set shorter as an intake air flow rate flowing through the intake port increases.

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