JP5002034B2 - Fuel control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel control device for an internal combustion engine applied to premixed compression ignition combustion of a combustion chamber direct injection gasoline engine that injects fuel directly into the combustion chamber.

In a conventional combustion chamber direct injection gasoline engine aimed at improving the fuel consumption of an internal combustion engine, stratified mixture lean combustion is effective as a combustion method for reducing pumping loss, and a wall guide method has been put into practical use. In this method, air-fuel mixture formation of the injected fuel and conveyance to the vicinity of the spark plug are performed by the air flow in the combustion chamber and the cavity provided in the piston.
However, because it aimed at fuel droplet splitting and evaporation promotion by collision with the piston cavity, fuel adhesion to the piston cavity was unavoidable, and burned gas performance and fuel consumption deteriorated due to increase in unburned components . Furthermore, if there is a fuel rich region in the stratified mixture, the temperature will increase during combustion and the thermal NOx concentration will increase. The burned gas in the stratified mixture lean combustion contains NOx and the reducing agents CO and HC and O2 at the same time, and NOx purification by the three-way catalyst is not possible. Installation of a catalyst is required.

  In contrast to the stratified mixture lean combustion, the premixed compression ignition combustion is such that the air-fuel mixture injected and homogenized in the intake stroke self-ignites in the high-temperature and high-pressure state of the compression stroke. In this premixed compression ignition combustion, the fuel is injected in the intake stroke, so there is no adhesion to the piston top surface or cylinder side surface, and the time required for the mixture formation is sufficient, and in the mixture in the latter half of the compression stroke. There is no overdense area. For this reason, the combustion temperature is lowered and thermal NOx is hardly generated. Accordingly, the premixed compression ignition combustion is being developed as a next generation combustion method.

  The combustion state of premixed compression ignition combustion is largely influenced by the mixture concentration and temperature, and does not ignite if the gas temperature during compression is lower than the self-ignition temperature. Therefore, in order to raise the temperature of the air-fuel mixture, increase the compression ratio of the engine, provide a negative overlap in the opening and closing timing of the intake and exhaust valves, leave high temperature residual gas in the combustion chamber, or intake air with an electric heater Measures such as heating are taken.

  By these measures, premixed compression ignition combustion can be realized stably in a partial operation state belonging to the light load region. However, when the air-fuel mixture concentration is high, the self-ignition temperature is low and the combustion speed increases when ignited, so that knocking due to abnormal pressure increase occurs. Therefore, premixed compression ignition combustion in a high load operation region where the fuel supply amount is large and the mixture concentration is high is limited. In order to establish premixed compression ignition combustion in this rich mixture state, it is necessary to suppress premature ignition and reduce the combustion speed. One way to achieve this is to use a fuel that has a characteristic that ignition temperature does not change significantly even when the mixture concentration is high, combustion speed is slow, pressure rise in the cylinder due to combustion is slow, and knocking is difficult to occur. It has been.

  As described above, a method of supplying fuel having characteristics corresponding to each combustion state in a wide operating region of an internal combustion engine has been proposed as a bi-fuel technology. For example, Patent Document 1 discloses a technique for injecting water in order to suppress pre-ignition combustion at the time of switching from normal spark ignition combustion to premix compression ignition combustion mode.

  Further, regarding the expansion of premixed combustion to a high-load operation state, for example, Patent Document 2 discloses that hydrogen gas having high antiknock performance is used as the second fuel. For example, Patent Document 3 discloses diethyl ether. Is disclosed. For example, Patent Document 4 discloses the use of gasoline and light oil.

JP 2006-17082 A (summary column, FIG. 1) JP 2004-100501 A (summary column, FIG. 1) JP 2008-286110 A (summary column, FIG. 2) JP 2009-68418 A (summary column, FIG. 1)

  As described above, in a wide operating range of an internal combustion engine, a bi-fuel that uses two types of fuel, a fuel having a normal anti-knock characteristic and a fuel having a high anti-knock characteristic, in order to have characteristics corresponding to respective combustion states. The system is being considered.

  However, since the intake air flow behavior of the internal combustion engine varies greatly from cycle to cycle, it is difficult to stably arrange the fuel supplied from the two fuel supply systems in layers or to mix them uniformly. For this reason, there is a problem that cycle fluctuations appear greatly in the air-fuel mixture formation, resulting in a decrease in combustion stability.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine that forms an air-fuel mixture with little cycle fluctuation and realizes stable premixed compression ignition combustion from a low load to a high load operation state. An object of the present invention is to provide a fuel control device.

A fuel control apparatus for an internal combustion engine according to the present invention includes a first fuel injection apparatus that directly injects a first fuel into a combustion chamber of the internal combustion engine, and an intake valve that controls introduction of intake air and fuel into the combustion chamber. Two intake pipes connected to the intake valve, one of the intake pipes, a swirl control valve that forms a swirl air flow in the combustion chamber, and the intake pipe is opened. A separator that is installed in the intake pipe and divides the intake pipe into two in the intake air introduction direction, and has an anti-knock characteristic higher than that of the first fuel outside the intake pipe divided into two by the separator. The second fuel injection device for injecting the second fuel and the crankshaft of the internal combustion engine rotate three times, so that an intake stroke, a compression heating stroke, a fuel mixing stroke, a compression stroke, a combustion stroke, and an exhaust stroke are performed. Have two journeys Based on the detection results of the intake / exhaust valve driving means for realizing cycle combustion, the operating condition detecting means for detecting the operating condition of the internal combustion engine, and the operating condition detecting means, or only the first fuel is injected, Combustion mode determining means for determining whether the first fuel and the second fuel are formed as a stratified mixture or intimately mixing, and mixing for determining the mixing ratio of the first fuel and the second fuel An internal combustion engine for controlling premixed compression ignition combustion in accordance with an operating state of the internal combustion engine, wherein normal gasoline is used as the first fuel, and the second fuel is used as the second fuel. A high octane fuel containing a large amount of aromatic components is injected, and only the first fuel is injected in a light load state, and a swirl flow is generated in the combustion chamber in a medium load state, in addition to the first fuel. Injecting a second fuel, furthermore, in the high load condition both to increase the injection quantity ratio of the second fuel, in which switching to 6 cycles combustion from 4 cycles combustion.

  According to this invention, the mixture distribution of the normal fuel and the high antiknock characteristic fuel is changed according to the operating state of the internal combustion engine, and the formation of the stratified mixture and the homogeneous mixture is determined according to the fuel distribution. A mixture with little fluctuation is formed, and stable premixed compression ignition combustion can be realized from a low load to a high load operation state.

1 is a schematic configuration diagram of an internal combustion engine to which a fuel control device for an internal combustion engine according to Embodiment 1 of the present invention is applied. It is a figure which shows the heat release rate behavior of the 1st fuel and the 2nd fuel which has a high antiknock characteristic. It is a combustion acupressure diagram at the time of use of the 1st fuel and the 2nd fuel which has a high antiknock characteristic. It is a figure explaining the operation | movement area | region of the fuel control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a combustion cycle, intake / exhaust valve operation, and fuel injection timing chart in the light load operation region. FIG. 4 is a shiatsu diagram and a fuel injection timing diagram in a light load operation region. It is a combustion chamber swirl flow control figure in a medium load operation. It is a combustion cycle, intake / exhaust valve operation, and fuel injection timing chart in the light load operation region. FIG. 4 is a shiatsu diagram and a fuel injection timing diagram in a middle load operation region. It is a figure which shows the high antiknock characteristic fuel ratio in each driving | operation area | region. It is a combustion cycle in the area | region in a high load driving | operation, an intake / exhaust valve operation | movement, and a fuel injection timing diagram. FIG. 4 is a shiatsu diagram and a fuel injection timing diagram in a high load operation region. 3 is a schematic flowchart showing the operation of the internal combustion engine fuel control apparatus according to Embodiment 1 of the present invention;

  Preferred embodiments of a fuel control device for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment, and includes various design changes.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of an internal combustion engine to which a fuel control device for an internal combustion engine according to Embodiment 1 is applied.
In FIG. 1, the code | symbol 1 has shown the combustion chamber. The combustion chamber 1 introduces intake air and fuel to form a combustible fuel mixture, and burns the mixture to convert the heat generated by the combustion reaction into the pressure of the working fluid. A piston 2 is provided in the combustion chamber 1 and is connected to a crankshaft 4 by a connecting rod 3. By connecting the connecting rod 3 and the crankshaft 4, the reciprocating sliding motion of the piston 2 is converted into the rotational motion of the crankshaft 4. The piston 2 slides in the combustion chamber 1 to introduce intake air into the combustion chamber 1, converts the combustion pressure of the air-fuel mixture into kinetic energy, and further burns the burned gas after combustion to the exhaust pipe. 5 is discharged.

  The crankshaft 4 is provided with a rotational speed sensor 6 and is configured to generate a specific number of pulses per one rotation of the crankshaft 4. Further, a specific angle, for example, a piston top dead center or a bottom dead center is made by one rotation. It is configured to generate a pulse at a point. And the signal of the crankshaft 4 is input into the engine control unit 7 mentioned later, and the piston position based on calculation of engine speed and one rotation specific position determination is calculated.

  On the top surface of the combustion chamber 1, a first injector 9 is installed as a combustion injection device that directly injects a first fuel 8, for example, gasoline, toward the piston 2. In addition, the combustion chamber 1 is driven by the magnetic force of the first electromagnetic coil 10, and an intake valve 11 that controls the introduction of intake air and fuel into the combustion chamber 1. An intake pipe 12 is provided for introduction into the combustion chamber 1. As will be described later, an intake pipe 12 is divided into two and connected to the intake valve 11. Further, the intake pipe 12 is provided with a second injector 14 as a combustion injection device that injects a second fuel 13 having a high anti-knock characteristic, for example, a high octane fuel containing a large amount of aromatic components. The spray shape and injection direction of the second fuel 13 injected from the second injector 14 are injected toward the intake valve 11 so that the amount of fuel adhering to the inner wall surface of the intake pipe 12 is minimized. Is set as follows.

  A throttle valve 15 that controls the flow rate of intake air flowing through the intake pipe 12 is installed in the middle of the intake pipe 12, and is configured to control the opening / closing amount of the throttle valve 15 by a throttle actuator 16 that is controlled by, for example, a DC motor or a stepping motor. Has been.

  Further, the combustion chamber 1 is provided with an exhaust valve 18 that is driven by the magnetic force of the second electromagnetic coil 17 to control the exhaust from the combustion chamber 1, and the burned gas from the combustion chamber 1 is exhausted from the exhaust pipe 5. Through the atmosphere. A three-way catalyst 19 is provided on the downstream side of the exhaust pipe 5. When the injected fuel burns at a stoichiometric air-fuel ratio at which it completely burns, the harmful effects of CO, HC, NOx contained in the burned gas The three gas components are redox-purified at the same time.

  An accelerator position sensor 20 is provided for converting the depression position of the accelerator pedal operated by the driver into an electric signal. A signal from the accelerator position sensor 20 and a signal from the rotation speed sensor 6 are taken into the engine control unit 7; In the engine control unit 7, the fuel injection amount and injection timing control injected from the first injector 9 and the second injector 14 and the intake / exhaust valve opening / closing operation are performed, and the opening / closing timing is changed to change the combustion cycle to 4 cycles. Further, in-cylinder air flow control is performed by a swirl control valve (shown in detail in FIG. 7), which will be described later, installed in the intake pipe 12.

FIG. 2 shows the heat release rate behavior of the first fuel 8 and the second fuel 13 having high antiknock characteristics. The horizontal axis of FIG. 2 indicates the crankshaft, and the vertical axis indicates the heat generation rate, and shows the heat generation rate behavior when the engine is operated by premixed compression ignition combustion using each fuel.
In FIG. 2, the code | symbol 21 shows the combustion behavior when the 1st fuel 8 is used, and combustion is completed at an early crank timing. Reference numeral 22 indicates the combustion behavior when the second fuel 13 having high anti-knock characteristics is used, and the combustion start timing is greatly delayed as compared with the combustion behavior 21 when the first fuel 8 is used. .

  In the light load operation state, the air-fuel ratio of the premixed gas is lean, and the pressure rise in the combustion chamber 1 is the limit of occurrence of knocking even in the early ignition and high-speed combustion shown in the heat release rate behavior 21 when the first fuel 8 is used. Is suppressed within. However, when shifting to the high-load operation state, the combustion speed exceeds the knocking generation limit due to the enrichment of the air-fuel ratio due to the increase in the fuel injection amount. At this time, when the second fuel 13 having high anti-knock characteristics is mixed, the heat generation rate behavior of the mixed fuel shows the characteristic of the heat generation rate behavior 23 obtained by synthesizing the heat generation rate behavior 22 and the heat generation rate behavior 21. The characteristics of the heat release rate behavior 23 indicate that the ignition performance is the same as that of the first fuel 8, but the combustion speed is slow and the combustion period is also long. Therefore, even when this mixed fuel is injected in a high-load operation state, knocking does not occur and stable combustion can be realized.

FIG. 3 shows the behavior of the pressure in the combustion chamber in a high load operation state when a fuel obtained by mixing the first fuel 8 and the first fuel 8 with the second fuel 13 having a high antiknock characteristic is used. FIG. 3 is an acupressure diagram in which the horizontal axis represents the crank angle and the vertical axis represents the pressure in the combustion chamber.
In FIG. 3, reference numeral 31 indicates a finger pressure diagram when the first fuel 8 is used, and the maximum pressure immediately after ignition is high, and knocking occurs as indicated by reference numeral 32 in the later stage of the expansion stroke. Reference numeral 33 shows a finger pressure diagram when the mixed fuel is used. The pressure increase after ignition is slow, the maximum pressure is low, and the combustion period is long. Therefore, it can be seen that the acupressure diagram 31 and the acupressure diagram 33 have substantially the same output, but the acupressure diagram 33 realizes stable combustion without causing knocking.

  FIG. 4 is a diagram for explaining an operation region of the fuel control device described in FIG. FIG. 4 shows the engine speed on the horizontal axis and the output on the vertical axis, and the line 41 indicates the maximum output torque. In this figure, a region 42 is a low-load operation region, and in this region there is little injected fuel and the air-fuel mixture is always in a lean state. Therefore, premixed compression ignition combustion is established only by the injection of the first fuel 8 from the first injector 9 into the combustion chamber 1 during the intake stroke.

  A region 43 is a medium load operation region, and knocking occurs only with the first fuel 8. However, in this region, the injection ratio of the second fuel 13 having high anti-knock characteristics is low, and a stratified mixture is formed in the outer peripheral portion of the combustion chamber 1 by the swirl air flow, and the second fuel 13 having the high anti-knock characteristic is formed in the central portion of the combustion chamber 1. A donut arrangement that forms an air-fuel mixture of one fuel 8 is adopted. According to this configuration, knocking occurs due to a decrease in the combustion speed of the high-pressure portion on the inner and outer periphery of the combustion chamber 1 without changing the premixed compression ignition performance from the central portion in the combustion chamber 1 even if the fuel is not homogeneously mixed. Can be suppressed.

  Region 44 is a high load operation region, and the air-fuel ratio is considerably richer than regions 42 and 43. Therefore, in order to realize premixed compression ignition combustion, it is necessary to further mix fuel with high antiknock characteristics. As indicated by a region 43, the fuel injected from the first injector 9 disposed in the combustion chamber 1 and the second injector 14 disposed in the intake port forms a layered mixture in the combustion chamber 1. . However, in the region 44, the mixing ratio of the second fuel 13 is high, and in order to achieve stable combustion, it is necessary to perform homogeneous mixing. In the conventional four-cycle combustion, the time required for mixing the first fuel 8 and the second fuel 13 cannot be taken. For this reason, in this embodiment, the combustion cycle is changed from 4 cycles to 6 cycles, and one rotation of the crankshaft is used as a mixture formation cycle. The air flow and fuel injection control in each operation region will be described below.

  FIG. 5 is a diagram showing an engine combustion cycle and fuel injection timing in the light load operation region. The combustion cycle in this operation region is a four-cycle combustion cycle in which the strokes of “intake”, “compression”, “combustion”, and “exhaust” are repeated at a crank angle of 180 ° and one cycle of 720 °. The valve lift behaviors of the exhaust valve 18 and the intake valve 11 are as indicated by reference numerals 51 and 52. Although the lift behavior shows a profile in cam drive, the lift behavior of the direct acting intake / exhaust valve is close to a rectangular wave. Reference numeral 53 denotes a first fuel injection pulse injected from the first injector 9, and fuel is directly injected into the combustion chamber 1 at the beginning of the intake stroke. In the light load region, the high anti-knock characteristic fuel is not injected from the second injector 14.

  FIG. 6 is a shiatsu diagram in which the horizontal axis indicates the cylinder volume and the vertical axis indicates the pressure in the combustion chamber 1. In this figure, the fuel injection timing shown in FIG. 5 is shown. The number of fuel injections is one, and the fuel is injected at the beginning of the intake stroke.

  In the light load operation state, the residual gas due to the intake stroke injection of the first fuel 8 by the first injector 9 and the negative overlap of the intake and exhaust valves 11 and 18 in the four-cycle combustion cycle in which the compression ratio of the engine is increased. Premixed compression ignition combustion by adiabatic temperature rise in the latter stage of the compression stroke with a high compression ratio can be realized. In this operation region, the fuel injection amount is small and the air-fuel ratio is lean, so that the combustion speed is suppressed and continuous operation can be performed without causing knocking.

  In the middle load operation state, the occurrence of knocking due to a rapid increase in the pressure in the combustion chamber 1 due to an increase in the combustion speed becomes a problem. Therefore, the second fuel 13 having a high anti-knock characteristic is used in this operation region.

  FIG. 7 is a diagram showing the behavior of the second fuel 13 having a high anti-knock characteristic injected from the second injector 14 in the medium load operation region. This figure shows a transverse section in the vicinity of the combustion chamber 1 with respect to the longitudinal sectional view shown in FIG.

  As shown in FIG. 7, in the fuel control device for an internal combustion engine according to the first embodiment, two intake pipes 12 are connected to the intake valve 11. A swirl control valve 71 is installed in the right port 12 a with respect to the inflow direction, and the opening degree is controlled by the stepping motor 72. When the swirl control valve 71 is closed, the intake air is sucked only from the port 12b on the left side with respect to the inflow direction of the sucked air, so that swirl flow can be generated in the combustion chamber 1. Further, a separator, for example, a separation plate 73, is provided at the center of the left port 12b to divide the left port 12b into two in the vertical direction, that is, the intake air inflow direction. Then, the second fuel 13 having a high anti-knock characteristic injected from the second injector 14 is introduced into the combustion chamber 1 through the outside of the separation plate 73, that is, the outside of the left port 12 b, and swirl flow 74. The air-fuel mixture is formed while riding. Further, the intake air 75 that flows in from the inside of the separation plate 73 stratifies the swirl flow 74 that is an air-fuel mixture of the second fuel 13 around the outer periphery of the combustion chamber 1.

  By forming such an air-fuel mixture, the air-fuel mixture 76 of the first fuel 8 causes premixed compression ignition combustion at the center portion in the combustion chamber 1 and becomes a high pressure state at the outer peripheral portion in the combustion chamber 1. Even so, the second fuel 13 having a high antiknock characteristic and a slow combustion rate burns slowly, so that the combustion reaction can be completed while suppressing the occurrence of knocking.

  FIG. 8 is a diagram showing an engine combustion cycle and fuel injection timing in a medium load operation region. An injection pulse 81 of the second fuel 13 by the second injector 14 is added to the light load state shown in FIG. As shown in FIG. 8, the second fuel 13 having a high anti-knock characteristic is injected into the intake port in the exhaust stroke, and is introduced into the combustion chamber 1 together with the swirl flow 74 by opening the intake valve 11. At the same time, in the intake stroke, the first fuel 8 is injected from the top surface of the combustion chamber 1 toward the piston 2 from the first injector 9, and the combustion chamber 1 has a high anti-knock characteristic at the outer peripheral portion. The air-fuel mixture including the second fuel and the first fuel 8 in the central portion is formed in a layered manner.

  FIG. 9 is a finger pressure diagram and a fuel injection timing diagram, where the horizontal axis indicates the cylinder volume and the vertical axis indicates the pressure in the combustion chamber 1. In this figure, the fuel injection timing shown in FIG. 8 is shown. The number of fuel injections is 2, and the fuel is injected at the beginning of the exhaust stroke and the intake stroke.

Next, a method for distributing the fuel injection amount between the first fuel 8 and the second fuel 13 having high antiknock characteristics will be described.
When both the first fuel 8 and the second fuel 13 are injected, the calorific value is expressed by equation (1).
Here, Q is the one-cycle injected fuel heat value (cal / cycle), C1 (cal / g) is the heat value of the first fuel 8, C2 (cal / g) is the heat value of the second fuel 13, and G1 (G / cycle) is the injection amount of the first fuel 8, and G 2 (g / cycle) is the injection amount of the second fuel 13.
Q = C1 * G1 + C2 * G2 (1)

The high anti-knock characteristic fuel ratio r is expressed by the following equation (2). Here, Gf (g / cycle) is the fuel injection amount when all the required calorific value Q is covered by the first fuel 8, as shown in the equation (3).
r = (C2 × G2) / (C1 × Gf) (2)
Q = C1 × Gf (3)
From Equation (1), Equation (2), and Equation (3), the first and second fuel injection amounts are distributed as shown in Equation (4) and Equation (5) according to the high anti-knock characteristic fuel ratio r. Is done.
G1 = Gf × (1−r) (4)
G2 = Gf × r × C1 / C2 (5)
Here, the high anti-knock characteristic fuel distribution ratio is set in accordance with the operating state. For example, changes in each operating region are set as shown below.
Low addition area r = 0
Medium load range 0 <r ≦ 0.4
High load region 0.4 <r ≦ 0.8

  FIG. 10 shows the setting of the high anti-knock characteristic fuel ratio r in each load region 44, 43, 42 represented by the engine speed and output.

  FIG. 11 is a diagram showing the combustion cycle, intake / exhaust valve behavior, and fuel injection timing in the high-load operation region. In the high load operation region, it is necessary to inject more second fuel 13 having a high anti-knock characteristic than in the medium load operation region, and in order to continue the premixed compression ignition combustion stably, the fuel mixing is extremely In this embodiment, fuel mixing is realized by a six-cycle combustion cycle.

  In FIG. 11, the valve opening lift behavior of the intake valve 11 starts to open before the top dead center of the intake stroke as indicated by reference numeral 91. The intake stroke starts from the top dead center of the intake stroke indicated by 0 °. The compression temperature rise process starts at 180 ° at the crank angle, and is completed at the compression top dead center of 360 °. The fuel mixing process is up to 540 °. The compression stroke is from 540 ° to 720 °, and the combustion stroke is from 720 ° to 900 °. The exhaust stroke is from 900 ° to 1080 °, and the exhaust valve 18 performs a valve opening operation as shown in the exhaust valve lift behavior 92 to exhaust the burned gas.

  As described above, the six-cycle combustion completes one cycle with three rotations of the crankshaft 4 and executes six strokes of “intake”, “compressed temperature rise”, “fuel mixing”, “compression”, “combustion”, and “exhaust”. . Corresponding to this 6-cycle combustion cycle, the second fuel 13 having a high anti-knock characteristic is injected at the timing indicated by reference numeral 93 in the exhaust stroke, and the first fuel 8 is injected at the timing indicated by reference numeral 94 in the fuel mixing stroke. The

  FIG. 12 is a finger pressure diagram and a fuel injection timing diagram, in which the horizontal axis indicates the cylinder volume and the vertical axis indicates the pressure in the combustion chamber 1. In this figure, the fuel injection timing shown in FIG. 10 is shown. The number of fuel injections is two, and the fuel is injected in the initial stage of the intake stroke and the fuel mixing stroke.

  Next, fuel control in the fuel control apparatus for an internal combustion engine according to the first embodiment will be described with reference to the flowchart of FIG. This flowchart shows an overall control flow of engine operation region determination, combustion cycle switching, and fuel injection.

  First, in step S101, the operation region Dr (n) at the current time n is determined from detection signals such as the engine speed and the accelerator pedal opening. A numerical value is stored in Dr (n) according to the operation region. For example, 1: light load region, 2: medium load region, 3: high load region.

  In step S102, the current n operation mode Dm (n) is input. For example, a 4: 4 cycle operation and a 6: 6 cycle operation are assumed.

  After inputting the operation region and the operation mode in step S101 and step S102, in step S103, the operation region is compared with the detection value at the previous n-1 timing. Here, the change in the operation region is expressed as an absolute value of Dr (n) −Dr (n−1), and when it is larger than 0, it is determined that the operation region has changed.

Next, it is determined whether or not it is necessary to change the combustion mode in each operation region.
First, in step S104, if it has changed to the light load operation state at the current timing n, it is determined in step S106 whether or not the operation mode at the previous n-1 timing was four-cycle combustion. If the previous operation mode is four-cycle combustion, there is no need to change the mode, so the fuel injection amount is calculated in step S107. In step S107, the fuel injection amount is calculated based on equations (4) and (5). Since the high anti-knock characteristic fuel ratio r is 0 in the light load operation region, G1 = Gf, and only the first injector 9 performs fuel injection.

  If the previous operation mode is not the four-cycle combustion mode in step S106, the crank angle advances to the intake TDC (Top Dead Center) at the combustion mode switching start timing as shown in step S108 in order to switch to the four-cycle combustion mode. In step S109, the mode is switched to the four-cycle combustion mode in which “intake”, “compression”, “combustion”, and “exhaust” are repeated with two rotations of the crank.

  Next, if it is determined in step S105 that the operation state has changed to the middle load operation state at the current n timing, it is determined in step S110 whether or not the operation mode at the previous n-1 timing was four-cycle combustion. Since it is not necessary to change the mode if it is four-cycle combustion, the fuel injection amount is calculated in step S113.

  In step S113, the fuel injection amount is calculated based on equations (4) and (5). In the middle load operation region, the high anti-knock characteristic fuel ratio r is changed in a range of 0 to 0.4 or less according to the load condition, and the injection amount G1 of the first fuel 8 and the injection amount G2 of the second fuel 13 are changed. Is calculated.

  If the previous operation mode is not four-cycle combustion, in order to switch to the four-cycle combustion mode, as shown in step S111, wait for the crank angle to advance to the intake TDC at the combustion mode switching start timing. Switch to a 4-cycle combustion mode that repeats “intake”, “compression”, “combustion”, and “exhaust”.

  If it is determined through steps S104 and S105 that the current state has changed to the high-load operation state at the timing n, the process proceeds to step S114 to switch the combustion mode to the 6-cycle combustion mode.

  In step S114, the process waits for the crank angle to advance to the intake TDC at the combustion mode switching start timing. In step S115, the crank is rotated three times to “intake”, “compressed temperature rise”, “fuel mixing”, “compression”, “combustion”. ”And“ exhaust ”are repeated to switch to the 6-cycle combustion mode.

  In step S116, the fuel injection amount is calculated based on equations (4) and (5). In the high load operation region, the high anti-knock characteristic fuel ratio r is changed in a range of 0.4 to 0.8 or less according to the load condition, and the injection amount G1 of the first fuel 8 and the injection of the second fuel 13 are changed. The amount G2 is calculated.

  As described above in detail, according to the fuel control apparatus for an internal combustion engine according to the first embodiment, the mixture distribution of the normal fuel and the high anti-knock characteristic fuel is changed according to the operating state of the internal combustion engine, and the fuel distribution Therefore, the formation of the stratified gas mixture and the formation of the homogeneous gas mixture are determined, so that a gas mixture with little cycle fluctuation can be formed, and stable premixed compression ignition combustion can be realized from a low load to a high load operation state.

DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Piston 3 Connecting rod 4 Crankshaft 5 Exhaust pipe 6 Rotational speed sensor 7 Engine control unit 8 First fuel 9 First injector 10 First electromagnetic coil 11 Intake valve 12 Intake pipe 12a, 12b Port 13 First Second fuel 14 Second injector 15 Throttle valve 16 Throttle actuator 17 Second electromagnetic coil 18 Exhaust valve 19 Three-way catalyst 20 Accelerator position sensor 71 Swirl control valve 72 Stepping motor 73 Separating plate 74 Swirl flow 75 Intake air 76 Mixture

Claims (2)

A first fuel injection device that directly injects a first fuel into a combustion chamber of an internal combustion engine;
An intake valve that controls the introduction of intake air and fuel into the combustion chamber;
Two intake pipes connected to the intake valve;
A swirl control valve that closes one of the intake pipes and forms a swirl air flow in the combustion chamber;
A separator that is installed in an open intake pipe among the intake pipes and divides the intake pipe into two in the direction of introduction of the intake air;
A second fuel injection device for injecting a second fuel having a higher anti-knock characteristic than the first fuel to the outside of the intake pipe divided into two by the separator;
Intake / exhaust valve drive means for realizing 6-cycle combustion having six strokes of an intake stroke, a compression heating stroke, a fuel mixing stroke, a compression stroke, a combustion stroke, and an exhaust stroke by rotating the crankshaft of the internal combustion engine three times When,
An operating state detecting means for detecting an operating state of the internal combustion engine;
Combustion for determining whether to inject only the first fuel, to form a stratified mixture of the first fuel and the second fuel, or to perform homogeneous mixing based on the detection result of the operating state detecting means Mode judging means;
Mixing ratio determining means for determining a mixing ratio of the first fuel and the second fuel;
In a fuel control device for an internal combustion engine that controls premixed compression ignition combustion according to the operating state of the internal combustion engine,
Injecting normal gasoline as the first fuel, high octane fuel containing a large amount of aromatic components as the second fuel,
In the light load state, only the first fuel is injected, in the middle load state, a swirl flow is generated in the combustion chamber, the second fuel is injected in addition to the first fuel, and in the high load state, A fuel control apparatus for an internal combustion engine, characterized by increasing the injection amount ratio of the second fuel and switching from 4-cycle combustion to 6-cycle combustion . A first fuel injection device that directly injects a first fuel into a combustion chamber of an internal combustion engine;
An intake valve that controls the introduction of intake air and fuel into the combustion chamber;
Two intake pipes connected to the intake valve;
A swirl control valve that closes one of the intake pipes and forms a swirl air flow in the combustion chamber;
A separator that is installed in an open intake pipe among the intake pipes and divides the intake pipe into two in the direction of introduction of the intake air;
A second fuel injection device for injecting a second fuel having a higher anti-knock characteristic than the first fuel to the outside of the intake pipe divided into two by the separator;
An intake / exhaust valve drive means for realizing 6-cycle combustion having six strokes of an intake stroke, a compression heating stroke, a fuel mixing stroke, a compression stroke, a combustion stroke, and an exhaust stroke by rotating the crankshaft of the internal combustion engine three times. When,
An operating state detecting means for detecting an operating state of the internal combustion engine;
Combustion for determining whether to inject only the first fuel, to form a stratified mixture of the first fuel and the second fuel, or to perform homogeneous mixing based on the detection result of the operating state detecting means Mode judging means;
Mixing ratio determining means for determining a mixing ratio of the first fuel and the second fuel;
In a fuel control device for an internal combustion engine that controls premixed compression ignition combustion according to the operating state of the internal combustion engine,
In the light load state, the first fuel is directly injected into the combustion chamber in an intake stroke in four-cycle combustion,
In an intermediate load state, the second fuel is injected in an exhaust stroke, and the second fuel is injected in an intake stroke in which a stratified mixture is formed in an outer peripheral portion of the combustion chamber,
A fuel control device for an internal combustion engine , wherein the second fuel is injected in an exhaust stroke and the first fuel is injected in a fuel mixing stroke of a six-cycle combustion cycle in a high load state .

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