JP4655809B2 - Different fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control technique for injecting a plurality of types of fuel from mutually different fuel injection valves.

Conventionally, in a compression ignition type internal combustion engine, two fuel injection valves for injecting different types of fuel are provided, and the two fuel injection valves are selectively used according to the engine operating state, so that premixed combustion and diffusion combustion are performed. A switchable technology is known.
(For example, see Patent Document 1).
JP 2004-197597 A JP 2004-308423 A

  By the way, depending on the operating conditions of the internal combustion engine, the consumption of fuel injected from each fuel injection valve is not necessarily equal, so it is conceivable that one fuel is lost before the other fuel. In such a case, the internal combustion engine may not be able to continue the desired operating state.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce consumption of various fuels in a heterogeneous fuel injection control apparatus including a plurality of fuel injection valves that inject different types of fuel. The present invention provides a technique that can make the remaining amounts of various fuels evenly or evenly.

  In order to solve the above-described problems, the present invention has produced a bias in consumption of various fuels in a heterogeneous fuel injection control device for an internal combustion engine having a plurality of fuel injection valves that inject different types of fuel. In this case, the greatest feature is that the consumption amounts of a plurality of types of fuels are made closer to each other evenly by increasing the injection frequency of the fuel with a small consumption amount.

  Specifically, the heterogeneous fuel injection control apparatus for an internal combustion engine according to the present invention includes a plurality of fuel injection valves that inject different types of fuel, an acquisition unit that acquires consumption amounts of the plurality of types of fuel, And an injection frequency changing means for increasing the injection frequency of the fuel with a small amount of consumption when a difference equal to or greater than a predetermined reference value occurs in the consumption amounts of the plurality of types of fuel.

  In the heterogeneous fuel injection control device for an internal combustion engine configured as described above, when a difference of the consumption amount of various fuels exceeds a reference value, the injection frequency of the fuel with a small consumption amount is increased from that point. If the injection frequency of the fuel with a small consumption amount is increased, the consumption amounts of the plurality of types of fuels are evenly approached, so that one fuel is prevented from being lost before the other fuels.

  In the present invention, the injection frequency changing means may increase the injection frequency of fuel with less consumption as the difference in consumption increases. When the difference in consumption is large, there is a possibility that fuel with a large consumption will be lost before the difference is reduced. On the other hand, if the frequency of fuel injection with less consumption is increased as the difference in consumption increases, it becomes easier to equalize the consumption before the fuel with more consumption disappears.

In the present invention, the injection frequency changing means may advance the change start timing of the injection frequency as the difference in consumption increases.

  If the difference in consumption is large, there is a possibility that fuel with a large consumption will be lost before the difference is reduced. On the other hand, if the change start of the injection frequency is advanced as the difference in consumption increases, it becomes easier to eliminate the difference in consumption before the fuel with much consumption disappears.

  In the present invention, the injection frequency changing means may change the size of the reference value in accordance with the type of fuel with a small consumption.

  When only one type of fuel remains among the multiple types of fuel, there is a possibility that the operating range in which appropriate combustion can be induced only by that fuel is narrower than other types of fuel (hereinafter, such a type of fuel). The type of fuel is referred to as the first fuel). Therefore, it is important to avoid a situation where only the first fuel remains.

  On the other hand, if the reference value when the consumption amount of the first fuel is smaller than that of the other fuel is set smaller than the reference value when the consumption amount of the other fuel is less than that of the first fuel, only the first fuel remains. The occurrence of the situation is easily avoided.

  Further, in the present invention, the change start timing of the injection frequency may be changed according to the type of fuel with a small amount of consumption.

  According to such a configuration, when the consumption amount of the first fuel is smaller than that of the other fuel, the change start timing of the injection frequency is advanced compared to the case where the consumption amount of the other fuel is smaller than that of the first fuel. The occurrence of a situation where only the first fuel remains is easily avoided.

  In the present invention, the injection frequency changing means increases the injection frequency of the low consumption fuel by injecting the low consumption fuel when the operating state of the internal combustion engine is in the injection region of the high consumption fuel. It may be.

  In the present invention, the injection frequency changing means may increase the injection frequency of the fuel with low consumption by performing post injection using the fuel with low consumption.

  Even if the type of fuel used for post-injection is changed, there is little effect on the combustion state of the internal combustion engine, so if post-injection is performed using fuel with low consumption, changes in the combustion state of the internal combustion engine are suppressed. The injection frequency of the low consumption fuel can be increased.

  As the plurality of types of fuels in the present invention, two types of fuels having different cetane numbers can be used. When the consumption of the high cetane fuel is less than that of the low cetane fuel, the injection frequency changing means is configured to reduce the low cetane fuel when the internal combustion engine is in a low rotation and low load operation state in the low cetane fuel injection region. Alternatively, the injection frequency of high cetane number may be increased by injecting high cetane number fuel.

  This is because when the internal combustion engine is in a low rotation and low load operation state, the in-cylinder pressure becomes low temperature and low pressure, so even if high cetane number fuel is injected instead of low cetane number fuel, problems such as pre-ignition It is because it is hard to produce.

  On the other hand, the injection frequency changing means reduces the injection amount of the high cetane fuel when the internal combustion engine is in a high rotation and high load operation state when the consumption amount of the low cetane fuel is small in the two types of fuel. At the same time, the injection amount of the low cetane fuel may be increased by increasing the injection amount of the low cetane fuel.

  This is because when the internal combustion engine is in a high speed and high load operation state, the in-cylinder pressure becomes high and high pressure, so that even if the injection amount of the low cetane fuel is increased, problems such as ignition delay and misfire occur. It is difficult.

  Next, in the present invention, as a method of increasing the injection frequency of fuel with low consumption, when fuel with high consumption is injected, fuel with low consumption is mixed with fuel with low consumption and injected. Thus, it is possible to exemplify a method of decreasing the injection frequency of fuel with a large amount of consumption while increasing the injection frequency of fuel with a small amount of consumption.

  Specifically, the heterogeneous fuel injection control device according to the present invention includes a plurality of fuel tanks that store a plurality of types of fuel, and a fuel that can selectively supply fuel from the plurality of fuel tanks to each fuel injection valve. An injection frequency changing means for injecting the one fuel injection from a fuel tank storing the fuel with a large amount of consumption when the fuel with a large amount of consumption is to be injected from one of the plurality of fuel injection valves. By reducing the amount of fuel supplied to the valve and controlling the fuel supply device to supply the fuel to the one fuel injection valve from the fuel tank storing the fuel with low consumption, the consumption is reduced. The frequency of fuel injection can be increased.

  At that time, a plurality of types of fuel are two types of fuels having different cetane numbers, and a plurality of fuel injection valves injects low cetane number fuel and a premixed combustion injection valve and diffusion combustion injects high cetane number fuel. If the fuel injection valve is used, the injection frequency changing means reduces the amount of low cetane fuel supplied to the premixed combustion fuel injection valve when the consumption of the low cetane fuel is greater than that of the high cetane fuel. In addition, the high cetane fuel is supplied to the premixed combustion injector, and if the consumption of the high cetane fuel is greater than the consumption of the low cetane fuel, the high cetane fuel supplied to the diffusion combustion injector is The fuel supply device may be controlled to reduce the amount and supply the low cetane number fuel to the diffusion combustion injection valve.

  Note that when the consumption of low cetane fuel is greater than the consumption of high cetane fuel, the ratio of the high cetane fuel to the low cetane fuel supplied to the premixed combustion injection valve is the load of the internal combustion engine. The lower cetane number fuel may be set such that the higher cetane number fuel increases and the lower cetane number fuel decreases.

  On the other hand, when the consumption of high cetane fuel is higher than the consumption of low cetane fuel, the ratio of high cetane fuel to low cetane fuel supplied to the diffusion combustion injector is high in the internal combustion engine load. It may be set so that the amount of high cetane number fuel decreases and the amount of low cetane number fuel increases.

  In addition, when the fuel tank for storing the low cetane number fuel becomes empty, the high cetane number fuel is injected from the premixed combustion injection valve and the diffusion combustion injection valve, and the fuel tank for storing the high cetane number fuel is empty. In this case, the low cetane number fuel may be injected only from the diffusion combustion injection valve.

  According to the present invention, in a heterogeneous fuel injection control device for an internal combustion engine having a plurality of fuel injection valves that inject fuels having different properties, the consumption of various fuels is equalized, or the remaining amount of various fuels is equalized. You can get closer.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. The internal combustion engine shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine).

  A cylinder 3 is formed in the cylinder block 2 of the internal combustion engine 1, and a piston 4 is replaced with the cylinder 3. A combustion chamber 40 is formed on the top surface of the piston 4.

  In the cylinder head 5, a center injector 6 is disposed substantially at the center of the surface facing the top surface of the piston 4. A side injector 7 is disposed at the edge of the surface of the cylinder head 5 that faces the top surface of the piston 4.

  The center injector 6 described above communicates with the first fuel tank 9 via the first fuel pipe 8. A first fuel pump 10 is arranged in the middle of the first fuel pipe 8. A first remaining amount sensor 11 that detects the remaining amount of fuel stored in the first fuel tank 9 is attached to the first fuel tank 9.

  The side injector 7 described above communicates with the second fuel tank 13 via the second fuel pipe 12. A second fuel pump 14 is disposed in the middle of the second fuel pipe 12. A second remaining amount sensor 15 that detects the remaining amount of fuel stored in the second fuel tank 13 is attached to the second fuel tank 13.

  The first fuel tank 9 stores a fuel having a higher cetane number than the second fuel tank 13 (for example, light oil), and the second fuel tank 13 has a fuel having a lower cetane number than that of the first fuel tank 9 (for example, Gasoline) is stored.

  The internal combustion engine 1 is provided with an ECU 16. The ECU 16 is an arithmetic logic circuit that includes a CPU, a ROM, a RAM, a backup RAM, and the like. In addition to the first remaining amount sensor 11 and the second remaining amount sensor 15 described above, detection signals from the accelerator position sensor 17 and the crank position sensor 18 are input to the ECU 16.

  Further, the ECU 16 determines the first fuel pump 10, the second fuel pump 14, the center based on the detection signal (accelerator opening Accp) of the accelerator position sensor 17 and the detection signal (engine speed Ne) of the crank position sensor 18. The injector 6 and the side injector 7 are electrically controlled.

  For example, in the so-called low / medium speed / low / medium load operation region where the load (accelerator opening degree Accp) and the engine speed Ne are relatively low, the ECU 16 operates from the initial stage to the middle stage (for example, before the top dead center of the compression stroke). 150 ° CA to 60 ° CA), a low cetane number fuel is injected from the side injector 7 to form a premixed gas in the combustion chamber 40 (in the cylinder 3), and then the center injector 6 near the top dead center of the compression stroke. By injecting high cetane fuel from the fuel, the premixed gas is burned using the high cetane fuel as an ignition source (premix combustion operation). Thus, the side injector 7 corresponds to the premixed combustion injection valve according to the present invention.

  Further, the ECU 16 injects high cetane number fuel from the center injector 6 in the vicinity of the compression top dead center in a so-called high rotation / high load operation region where the load (accelerator opening degree Accp) and the engine speed Ne become high. Thus, the high cetane fuel is burned while being diffused into the combustion chamber (diffusion combustion operation). Thus, the center injector 6 corresponds to the diffusion combustion injection valve according to the present invention.

By the way, depending on the operating conditions of the internal combustion engine 1 and the fuel supply conditions, the consumption rate (consumption per unit time) and remaining amount of high cetane number fuel and low cetane number fuel may not be equal. In such a case, only one of the high cetane number fuel in the first fuel tank 9 and the low cetane number fuel in the second fuel tank 13 may be emptied first.

  When the high cetane number fuel in the first fuel tank 9 becomes empty, it becomes necessary to continue the operation of the internal combustion engine 1 with only the low cetane number fuel in the second fuel tank 13. Low cetane number fuel is less ignitable than high cetane number fuel, so high cetane number fuel is used in the operating range where the temperature and pressure in the cylinder are likely to be high (the operating range where the load and engine speed are relatively high). It can be used as an alternative fuel.

  However, in the operation region where the inside of the cylinder is likely to be low temperature and low pressure (operation region where the load and the engine speed are extremely low), stable combustion occurs even if low cetane number fuel is injected instead of high cetane number fuel. It may not be possible.

  Further, when the low cetane number fuel in the second fuel tank becomes empty, it becomes necessary to continue the operation of the internal combustion engine 1 with only the high cetane number fuel in the first fuel tank 9. If premixed gas is formed using high cetane number fuel instead of low cetane number fuel in the premixed combustion operation region, the premixed gas will ignite prematurely when the internal combustion engine is in medium load / medium speed operation. Or, the generation amount of NOx may increase.

  Therefore, when fuel having different properties is injected from the two injectors 6 and 7 as in the internal combustion engine 1, either the high cetane number fuel in the first fuel tank 9 or the low cetane number fuel in the second fuel tank 13 is selected. It is necessary to avoid the situation where one side becomes empty first.

  On the other hand, the ECU 16 of the present embodiment forcibly increases the injection frequency of the fuel with a large remaining amount when the consumption rate or the remaining amount of the high cetane number fuel and the low cetane number fuel is biased. One of the high cetane number fuel and the low cetane number fuel is prevented from becoming empty first.

  Specifically, as shown in FIG. 2, the ECU 16 determines the remaining amount Rh of the high cetane number fuel stored in the first fuel tank 9 and the remaining amount Rl of the low cetane number fuel stored in the second fuel tank 13. The difference ΔC (= Cl−Ch) between the consumption rate Ch of the high cetane fuel and the consumption rate Cl of the low cetane fuel when the remaining amount Min (Rh, Rl), whichever is smaller, becomes equal to or less than the reference value Rbase ) Is within a predetermined allowable range Y (a region indicated by hatching in FIG. 2).

  When the difference ΔC is within the allowable range Y as indicated by points a and b in FIG. 2, the ECU 16 does not change the injection frequency of the high cetane fuel and the low cetane fuel and changes the injection frequency of the internal combustion engine 1. Continue driving.

  On the other hand, when the difference ΔC deviates from the allowable range Y as indicated by points A and B in FIG. 2, the ECU 16 forcibly changes the injection frequency of the high cetane number fuel and the low cetane number fuel. The operation of the internal combustion engine 1 is continued.

  As indicated by a point A in FIG. 2, the consumption rate Cl of the low cetane fuel is smaller than the consumption rate Ch of the high cetane fuel (Rl> Rh), and the difference ΔC is within the allowable range Y. When deviating, the ECU 16 increases the injection frequency of the low cetane number fuel.

  FIG. 3 is a diagram showing a change in the consumption rate difference ΔC when the injection frequency of the low cetane number fuel is increased from the time when the remaining amount Rh of the high cetane number fuel becomes equal to or less than the reference value Rbase.

  The dotted line in FIG. 3 shows the change in the consumption rate difference ΔC when the injection frequency of the low cetane number fuel and the high cetane number fuel is not changed, and the solid line in FIG. 3 shows the injection frequency of the low cetane number fuel. The change in the consumption rate difference ΔC when changed is shown.

  If the injection frequency of the low cetane number fuel and the high cetane number fuel is not changed, the difference in consumption rate ΔC remains deviated from the allowable range Y until the remaining amount Rh of the high cetane number fuel becomes zero. is doing. For this reason, when the remaining amount Rh of the high cetane number fuel becomes zero (point A0 in FIG. 3), a relatively large amount of low cetane number fuel remains.

  On the other hand, when the injection frequency of the low cetane fuel is increased from the time when the remaining amount Rh of the high cetane fuel becomes equal to or less than the reference value Rbase, the consumption rate difference ΔC is within the allowable range Y from the point A. It changes to the point A1, and also changes within the allowable range Y until the remaining amount Rh of the high cetane number fuel becomes zero. As a result, when the remaining amount Rh of the high cetane number fuel becomes zero (point A2 in FIG. 3), the remaining amount Rl of the low cetane number fuel becomes small.

  Therefore, when the injection frequency of the low cetane fuel is forcibly increased from the time when the remaining amount Rh of the high cetane fuel becomes equal to or less than the reference value Rbase, the consumption rates Ch, Cl of the high cetane fuel and the low cetane fuel are increased. In addition, the remaining amounts Rh and Rl can be made substantially equal.

  Next, as indicated by point B in FIG. 2, the consumption rate Ch of the high cetane fuel is small compared to the consumption rate Cl of the low cetane fuel (Rh> Rl), and the difference ΔC is allowable. When deviating from the range Y, the ECU 16 increases the injection frequency of the high cetane fuel.

  FIG. 4 is a diagram showing a change in the consumption rate difference ΔC when the injection frequency of the high cetane fuel is increased from the time when the remaining amount Rl of the low cetane fuel becomes equal to or less than the reference value Rbase.

  The dotted line in FIG. 4 shows the change in the consumption rate difference ΔC when the injection frequency of the low cetane number fuel and the high cetane number fuel is not changed, and the solid line in FIG. 4 shows the injection frequency of the high cetane number fuel. The change in the consumption rate difference ΔC when changed is shown.

  When the injection frequency of the low cetane number fuel and the high cetane number fuel is not changed, the difference in consumption rate ΔC remains deviated from the allowable range Y until the remaining amount Rl of the low cetane number fuel becomes zero. is doing. For this reason, when the remaining amount Rl of low cetane number fuel becomes zero (point B0 in FIG. 4), a relatively large amount of high cetane number fuel remains.

  On the other hand, when the injection frequency of the high cetane fuel is increased from the time when the remaining amount Rh of the low cetane fuel becomes equal to or less than the reference value Rbase, the consumption rate difference ΔC is within the allowable range Y from the point B. After the transition to the point B1, the allowable range Y is shifted until the remaining amount Rl of the low cetane number fuel becomes zero. As a result, when the remaining amount Rl of the low cetane number fuel becomes zero (point B2 in FIG. 4), the remaining amount Rl of the low cetane number fuel becomes small.

  Therefore, if the injection frequency of the high cetane fuel is forcibly increased from the time when the remaining amount Rl of the low cetane fuel becomes equal to or less than the reference value Rbase, the consumption rates Ch, Cl of the high cetane fuel and the low cetane fuel are increased. In addition, the remaining amounts Rh and Rl can be made substantially equal.

  The reference value Rbase described above may be a constant value, but may be variable according to the absolute value (= | ΔC |) of the difference ΔC in consumption rate. For example, as shown in FIG. 5, when the absolute value of the consumption rate difference ΔC becomes very large when the remaining amount Rl of the low cetane fuel falls below the reference value Rbase (point B ′ in FIG. 5). Even if the injection frequency is changed from that time, the remaining amount Rl of the low cetane fuel may become zero before the consumption rate difference ΔC converges to the allowable range Y.

On the other hand, as shown in FIG. 6, the reference value Rba increases as the absolute value of the consumption rate difference ΔC increases.
The reference value Rbase may be set to decrease as se increases and the absolute value of the consumption rate difference ΔC decreases.

  In this case, since the change in the injection frequency is started before the absolute value of the consumption rate difference ΔC becomes excessively large (point B4 in FIG. 6), the consumption rate difference ΔC is the remaining amount of low cetane fuel. Before the quantity Rl becomes zero, the point shifts to a point B5 within the allowable range Y.

  Further, the amount of change when changing the injection frequency may be a constant value, but may be variable according to the magnitude of the absolute value of the difference ΔC in consumption rate. If the change amount is constant, as shown in FIG. 5 described above, the absolute value of the difference ΔC in the consumption rate becomes very large when the remaining amount Rl of the low cetane fuel falls below the reference value Rbase. (Point B ′ in FIG. 5) Even if the injection frequency is changed from that point, the remaining amount Rl of the low cetane fuel becomes zero before the consumption rate difference ΔC converges to the allowable range Y. There is a possibility.

  On the other hand, as shown in FIG. 7, the amount of change in the injection frequency is increased as the absolute value of the difference ΔC in the consumption rate when the remaining amount Rl of the low cetane fuel falls below the reference value Rbase. May be.

  In this case, even if the reference value Rbase is fixed at a fixed value (that is, the injection frequency change start time is fixed at a fixed time), the difference in consumption rate before the remaining amount Rl of the low cetane number fuel becomes zero Δ C can be converged within the allowable range Y.

  At this time, as shown in FIG. 8, the low cetane number fuel remaining amount Rl is below the reference value Rbase and the consumption rate difference ΔC is larger than the allowable range Y (that is, the injection frequency of the high cetane number fuel is increased). May be divided into a plurality of regions according to the absolute value of the consumption rate difference ΔC, and the amount of change in the injection frequency may be different for each of the divided regions. It should be noted that the amount of change in each region is determined so as to increase as the absolute value of the consumption rate difference ΔC increases.

  Further, the reference value Rbase described above may be varied depending on the type of fuel. When the injection frequency is changed by the various methods as described above, the consumption rates Cl and Ch and the remaining amounts Rl and Rh of the low cetane number fuel and the high cetane number fuel become substantially equal. When the remaining amount of fuel becomes zero, the other fuel may remain slightly.

  In such a case, if refueling is not performed immediately, it is necessary to continue the operation of the internal combustion engine 1 with only one type of remaining fuel. When the remaining fuel is a high cetane fuel, the high cetane fuel can be ignited and burned in a relatively wide operating region of the internal combustion engine 1. However, when the remaining fuel is a low cetane number fuel, it may be difficult to ignite and burn the low cetane number fuel in the low load / low speed operation region of the internal combustion engine 1. This is because the ignitability of a low cetane fuel at a low temperature or low pressure is lower than that of a high cetane fuel.

  On the other hand, when the consumption rate Cl of the low cetane fuel is lower than the consumption rate Ch of the high cetane fuel (when the remaining amount Rl of the low cetane fuel is larger than the remaining amount Rh of the high cetane fuel), The injection frequency is changed earlier than when the consumption rate Ch of the low-valent fuel is lower than the consumption rate Cl of the low-cetane fuel (when the remaining amount Rh of the high cetane fuel is larger than the remaining amount Rl of the low cetane fuel). In this way, the reference value Rbase may be determined.

Specifically, as shown in FIG. 9, when the consumption rate Ch of the high cetane fuel is lower than the consumption rate Cl of the low cetane fuel, the remaining amount Rl of the low cetane fuel is less than or equal to the first reference value Rlbase. On the other hand, the change in the injection frequency is started from the time point, whereas when the consumption rate Cl of the low cetane fuel is lower than the consumption rate Ch of the high cetane fuel, the remaining amount Rh of the high cetane fuel is the first reference The change of the injection frequency may be started from the time when the value becomes equal to or less than the second reference value Rhbase that is larger than the value Rlbase.

  In this way, if the magnitude of the reference value Rbase is changed according to the type of fuel (in other words, the change start timing of the injection frequency is changed according to the type of fuel), the high cetane number is higher than the low cetane number fuel. It is possible to avoid a situation in which the fuel remaining amount Rh becomes zero. As a result, after the remaining amount of one of the two types of fuel becomes zero (in this case, the remaining amount Rl of the low cetane number fuel is zero), the other fuel (in this case, the high cetane number fuel) ) Makes it possible to continue the operation of the internal combustion engine 1.

  Hereinafter, specific examples of the method for changing the injection frequency will be described.

First, a first embodiment of the injection frequency changing method will be described with reference to FIGS.
As shown in FIG. 3 described above, if the difference in consumption rate ΔC exceeds the allowable range when the remaining amount Rh of the high cetane fuel falls below the reference value Rbase, the ECU 16 Increase the injection frequency and decrease the injection frequency of high cetane fuel.

  At this time, if the injection frequency of the high cetane fuel is reduced and the injection frequency of the low cetane fuel is increased in the premixed combustion operation region, the ignitability of the fuel may be lowered. Therefore, the ECU 16 increases the injection frequency of the low cetane number fuel and decreases the injection frequency of the high cetane number fuel in the diffusion combustion operation region.

  FIG. 10 is a timing chart showing operation modes of the center injector 6 and the side injector 7 in the diffusion combustion operation region. FIG. 10A shows an operation mode when the consumption rate difference ΔC is within the allowable range Y. FIG. When the consumption rate difference ΔC is within the allowable range Y, the ECU 16 causes the center injector 6 to perform pilot injection and main injection of high cetane fuel without operating the side injector 7.

  On the other hand, when the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16 stops the pilot injection from the center injector 6 as shown in FIG. 7 pilot injection of low cetane number fuel.

  In this case, in the diffusion combustion operation region, the injection frequency of the high cetane number fuel decreases and the injection frequency of the low cetane number fuel increases. As a result, the consumption rate Ch of the high cetane fuel decreases, and at the same time, the consumption rate Cl of the low cetane fuel increases.

  Further, as shown in FIG. 10C, the ECU 16 may reduce the main injection amount from the center injector 6 in addition to stopping the pilot injection from the center injector 6. At this time, the amount of decrease in the main injection is compensated by increasing the pilot injection amount from the side injector 7.

  When the injection amounts of the center injector 6 and the side injector 7 are controlled in this way, the degree of decrease in the consumption rate Ch of the high cetane fuel and the consumption rate of the low cetane fuel as compared with FIG. Since the increase degree of Cl becomes large, it becomes easy to eliminate the consumption rate difference ΔC in a short time.

When the absolute value of the consumption rate difference ΔC is excessively large, the ECU 16 may limit the operation state of the internal combustion engine 1 to the premixed combustion operation. According to such a method, the consumption rate Ch of the high cetane fuel is greatly reduced, and the consumption rate Cl of the low cetane fuel is greatly increased. Therefore, even when the absolute value of the consumption rate difference ΔC is relatively large, the consumption rate difference ΔC tends to fall within the allowable range Y before the remaining amount Rh of the high cetane fuel becomes zero. Become.

  Next, as shown in FIG. 4 described above, if the difference in consumption rate ΔC exceeds the allowable range Y when the remaining amount Rl of the low cetane fuel falls below the reference value Rbase, the ECU 16 The injection frequency of the low cetane fuel is decreased at the same time as the injection frequency of the cetane fuel is increased.

  At this time, when the premixed combustion operation is performed using the high cetane number fuel instead of the low cetane number fuel in the premixed combustion operation region, the load (accelerator opening Accp) and the engine speed Ne in the premixed combustion operation region are performed. High cetane fuels can ignite prematurely when is relatively high. Accordingly, the ECU 16 performs the premixed combustion operation with the high cetane fuel only when the load (accelerator opening degree Accp) and the engine speed Ne are low in the premixed combustion operation region.

  FIG. 11 is a diagram showing a diffusion combustion operation region and a premixed combustion operation region of the internal combustion engine 1. FIG. 11A shows the diffusion combustion operation region and the premixed combustion operation region when the consumption rate difference ΔC is within the allowable range Y.

  When the consumption rate difference ΔC is within the allowable range Y, the ECU 16 performs the premixed combustion operation (injection of the low cetane fuel from the initial stage of the compression stroke to the middle stage) in the low / medium load / low / medium speed operation region of the internal combustion engine 1. Injection of high cetane number fuel near the compression top dead center) and diffusion combustion operation (high cetane number fuel injection near the compression top dead center) in the high load / high rotation operation region.

  On the other hand, when the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16, as shown in FIG. Premixed combustion operation using only high cetane number fuel when the engine speed Ne is low (high cetane number fuel injection from the early stage to the middle of the compression stroke, or high cetane number fuel injection and compression top dead from the early stage to the middle of the compression stroke) (Injection with high cetane fuel near the point).

  Thus, when the premixed combustion operation using only the high cetane number fuel is performed when the load (accelerator opening degree Accp) and the engine speed Ne of the internal combustion engine 1 are low in the premixed combustion operation region, the low cetane number fuel is reduced. Since the used premixed combustion operation region is narrowed, the injection ratio Cl of the low cetane number fuel decreases, and at the same time the consumption rate Ch of the high cetane number fuel increases.

  Further, as shown in FIG. 11C, the ECU 16 changes the medium load / medium rotation operation region of the internal combustion engine 1 from the premix combustion operation region to the diffusion combustion operation region, thereby changing the premix combustion operation region. You may make it narrow.

  Next, a second embodiment of the injection frequency changing method will be described with reference to FIG. In the exhaust system of the internal combustion engine 1, an exhaust purification device such as a particulate filter, an oxidation catalyst, and a NOx catalyst is disposed. When such an exhaust purification device is activated early or when the purification capacity is regenerated, unburned fuel is injected into the exhaust purification device by injecting fuel (post-injection) from the injector in the cylinder of the exhaust stroke. May be supplied.

  In such a case, if the consumption rate difference ΔC deviates from the allowable range, the ECU 16 performs post injection or after injection using fuel with a low consumption rate.

  For example, as shown in FIG. 12, when the remaining amount Rh of the high cetane fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC exceeds the allowable range Y, the ECU 16 uses the low cetane fuel. Post injection (that is, post injection from the side injector 7) is performed. On the other hand, when the remaining amount Rl of the low cetane number fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC exceeds the allowable range Y, the ECU 16 performs post-injection using the high cetane number fuel (that is, the center injector). Post-injection from 6).

  Thus, if post-injection is performed using the fuel with the lower consumption rate of the high cetane number fuel and the low cetane number fuel, the injection frequency of fuel with a low consumption rate (fuel with a large remaining amount) can be increased. It becomes possible. Further, since the post-injected fuel hardly contributes to the combustion and output of the internal combustion engine 1, it is possible to minimize the change in the operating state of the internal combustion engine 1 even if the type of post-injected fuel is changed. It becomes.

  Next, a third embodiment of the injection frequency changing method will be described with reference to FIG. In the second embodiment described above, an example in which the difference ΔC in consumption rate is reduced by switching the type of post-injected fuel has been described. In this embodiment, the fuel is injected from an addition valve attached to the exhaust system. An example of reducing the consumption rate difference ΔC by switching the type of fuel will be described.

  FIG. 13 is a diagram showing a schematic configuration of an internal combustion engine to which the present embodiment is applied. In FIG. 13, a fuel addition valve 19 for adding fuel to the exhaust gas flowing through the exhaust passage 100 is attached to the exhaust passage 100 of the internal combustion engine 1.

  The fuel addition valve 19 is connected to the three-way switching valve 20 via the third fuel pipe 20. A fourth fuel pipe 22 and a fifth fuel pipe 23 are connected to the three-way switching valve 20. The fourth fuel pipe 22 communicates with the second fuel pipe 12, and the fifth fuel pipe 23 communicates with the first fuel pipe 8. The three-way switching valve 20 is a valve that selectively connects one of the fourth fuel pipe 22 and the fifth fuel pipe 23 to the third fuel pipe 20.

  In the internal combustion engine 1 configured as described above, the ECU 16 inputs the detection signals of the first remaining amount sensor 11 and the second remaining amount sensor 15 when adding fuel from the fuel addition valve 19, and generates high cetane number fuel. It is determined whether or not the remaining amount Rh, Rl of any one of the low cetane number fuels is less than or equal to the reference value Rbase.

  When the remaining amount Rh, Rl of either the high cetane number fuel or the low cetane number fuel is equal to or less than the reference value Rbase, the ECU 16 determines whether the consumption rate difference ΔC is within the allowable range Y. Determine. When the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16 controls the three-way switching valve 20 to inject fuel with a low consumption rate (a large remaining amount) from the fuel addition valve 19.

  For example, as shown in FIG. 3 described above, when the remaining amount Rh of the high cetane fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16 The three-way switching valve 20 is controlled so that the four fuel pipes 22 are electrically connected to the third fuel pipe 20, and then the fuel addition valve 19 is opened. When the fuel addition valve 19 and the three-way switching valve 20 are controlled in this way, the consumption rate Cl of the low cetane number fuel can be increased without affecting the combustion state of the internal combustion engine 1 or the like.

On the other hand, as shown in FIG. 4 described above, when the remaining amount Rl of the low cetane fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16 The three-way switching valve 20 is controlled so that the fifth fuel pipe 23 is electrically connected to the third fuel pipe 20, and then the fuel addition valve 19 is opened. When the fuel addition valve 19 and the three-way switching valve 20 are controlled in this way, the consumption rate Ch of the high cetane fuel can be increased without affecting the combustion state of the internal combustion engine 1 and the like.

  Next, a fourth embodiment of the injection frequency changing method will be described with reference to FIGS. FIG. 14 is a diagram showing a schematic configuration of an internal combustion engine to which the present embodiment is applied.

  In FIG. 14, the first fuel pipe 8 is branched into a first branch pipe 80 and a second branch pipe 81 on the way. The first branch pipe 80 is connected to the first fuel tank 9, and the second branch pipe 81 is connected to the second fuel tank 13. A first flow rate adjusting valve 82 is disposed at a portion where the first fuel pipe 8 branches into a first branch pipe 80 and a second branch pipe 81.

  The first flow rate adjusting valve 82 is configured such that the amount of fuel flowing into the first fuel pipe 8 from the first branch pipe 80 (amount of high cetane number fuel) and the amount of fuel flowing into the first fuel pipe 8 from the second branch pipe 81 ( It is a valve that adjusts the ratio of the amount of low cetane fuel.

  The second fuel pipe 12 is branched into a third branch pipe 120 and a fourth branch pipe 121 from the middle. The third branch pipe 120 is connected to the second fuel tank 13, and the fourth branch pipe 121 is connected to the first fuel tank 9. A second flow rate adjustment valve 122 is disposed at a portion where the second fuel pipe 12 branches into the third branch pipe 120 and the fourth branch pipe 121.

  The second flow rate adjusting valve 122 is configured such that the amount of fuel flowing into the second fuel pipe 12 from the third branch pipe 120 (the amount of low cetane number fuel) and the amount of fuel flowing into the second fuel pipe 12 from the fourth branch pipe 121 ( This is a valve that adjusts the ratio of the amount of high cetane fuel.

  The first branch pipe 80, the second branch pipe 81, the first flow rate adjustment valve 82, the third branch pipe 120, the fourth branch pipe 121, and the second flow rate adjustment valve 122 described above are included in the fuel supply apparatus according to the present invention. One embodiment.

  In the internal combustion engine 1 configured as described above, the ECU 16 determines that the difference ΔC between the consumption rate Ch of the high cetane number fuel and the consumption rate Cl of the low cetane number fuel is within the allowable range Y, FIG. As shown in FIG. 16, the first flow rate adjustment valve 82 and the second flow rate adjustment valve 122 are controlled.

  FIG. 15 is a diagram illustrating the flow of fuel when the internal combustion engine 1 is started and during warm-up operation (during cold operation). Since the in-cylinder temperature and the in-cylinder pressure are low during the start-up and warm-up operation of the internal combustion engine 1, poor ignition and misfire are likely to occur even when low cetane number fuel is injected.

  Therefore, the ECU 16 is configured to cause the first flow rate adjustment valve 82 and the second flow rate adjustment valve 122 to inject only the high cetane fuel from both the center injector 6 and the side injector 7 at the time of starting and warming up the internal combustion engine 1. To control.

  That is, the ECU 16 controls the first flow rate adjustment valve 82 so that the first fuel pipe 8 is connected only to the first branch pipe 80 at the time of start-up and warm-up operation of the internal combustion engine 1, and the second fuel pipe. The second flow rate adjusting valve 122 is controlled so that 12 is electrically connected only to the fourth branch pipe 121.

  When the first flow rate adjustment valve 82 and the second flow rate adjustment valve 122 are controlled in this way, only high cetane fuel with high ignitability is supplied, so that startability and combustion stability after start are improved. Is possible.

FIG. 16 is a diagram illustrating the flow of fuel after the warm-up of the internal combustion engine 1 is completed (during warm operation). After the warm-up of the internal combustion engine 1 is completed, the in-cylinder pressure and the in-cylinder temperature are increased to some extent, so that ignition failure and misfire are less likely to occur even when a premixed combustion operation using a low cetane number fuel is performed.

  Therefore, after the warm-up of the internal combustion engine 1 is completed, the ECU 16 causes the first flow rate adjustment valve 82 and the second flow control valve 82 so that the high cetane number fuel is injected from the center injector 6 and the low cetane number fuel is injected from the side injector 7. 2 The flow rate adjusting valve 122 is controlled.

  That is, after the warm-up of the internal combustion engine 1 is completed, the ECU 16 controls the first flow rate adjustment valve 82 so that the first fuel pipe 8 is electrically connected only to the first branch pipe 80, and the second fuel pipe 12 is The second flow rate adjustment valve 122 is controlled so as to be electrically connected only to the three branch pipe 120.

  At this time, if the operation state of the internal combustion engine 1 is in the premixed combustion operation region, the ECU 16 injects low cetane number fuel from the side injector 7 from the initial stage to the middle stage of the compression stroke to enter the combustion chamber 40 (inside the cylinder 3). The premixed gas is then formed, and then the high cetane number fuel is injected from the center injector 6 in the vicinity of the top dead center of the compression stroke, whereby the premixed gas is combusted using the high cetane number fuel as an ignition source. If the operation state of the internal combustion engine 1 is in the diffusion combustion operation region, the ECU 16 diffuses the high cetane fuel into the combustion chamber by injecting the high cetane fuel from the center injector 6 in the vicinity of the compression top dead center. Let it burn.

  Next, as shown in FIG. 3 described above, when the remaining amount Rh of the high cetane fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC deviates from the allowable range Y, the ECU 16 First, as shown in FIG. 17, the first flow rate adjusting valve 82 is controlled so that the first fuel pipe 8 is connected to both the first branch pipe 80 and the second branch pipe 81, and the second fuel pipe 12 is The second flow rate adjustment valve 122 is controlled so as to be electrically connected only to the three branch pipe 120.

  Subsequently, the ECU 16 causes the center injector 6 and the first fuel pump 10 to inject the mixed fuel of the high cetane number fuel and the low cetane number fuel from the center injector 6 when the operation state of the internal combustion engine 1 is in the diffusion combustion operation region. To control.

  When the mixed fuel of high cetane number fuel and low cetane number fuel is injected from the center injector 6 in the diffusion combustion operation region, the injection frequency (injection amount) of the high cetane number fuel decreases and the injection frequency of the low cetane number fuel (injection frequency ( (Injection amount) increases. As a result, the consumption rate difference ΔC can be reduced.

  In the diffusion combustion operation region, as the load (accelerator opening Accp) increases, the in-cylinder pressure and the in-cylinder temperature increase. As shown in FIG. 18, the ECU 16 increases the load (accelerator opening Accp) in the mixed fuel. The opening degree of the first flow rate adjustment valve 82 may be controlled so that the amount of low cetane number fuel is large and the amount of high cetane number fuel is small. In this case, the injection frequency of the low cetane number fuel can be increased while suppressing a decrease in ignitability.

  Further, the ECU 16 adjusts the first flow rate so that the absolute value (= | ΔC |) of the consumption rate difference ΔC increases, so that the amount of low cetane number fuel in the mixed fuel increases and the amount of high cetane number fuel decreases. The opening degree of the valve 82 may be controlled. According to such control, even if the absolute value of the difference ΔC in the consumption rate is large, the difference ΔC in the consumption rate is within the allowable range Y before the remaining amount Rh of the high cetane fuel becomes zero. It becomes easy to converge to.

  However, if the amount of low cetane number fuel injected from the center injector 6 in the diffusion combustion operation region is increased, the ignition delay period may become longer. Therefore, the amount of low cetane number fuel injected at the time of pilot injection is reduced. You may make it increase.

  When the remaining amount Rl of the low cetane fuel is equal to or less than the reference value Rbase and the consumption rate difference ΔC deviates from the allowable range Y as shown in FIG. As shown, the first flow rate adjusting valve 82 is controlled so that the first fuel pipe 8 is connected to only the first branch pipe 80, and the second fuel pipe 12 is connected to the third branch pipe 120 and the fourth branch pipe 121. The second flow rate adjustment valve 122 is controlled so as to be electrically connected to both.

  Subsequently, the ECU 16 causes the side injector 7 and the second fuel pump to inject the mixed fuel of the high cetane number fuel and the low cetane number fuel from the side injector 7 when the operation state of the internal combustion engine 1 is in the premixed combustion operation region. 14 is controlled.

  When the mixed fuel of high cetane number fuel and low cetane number fuel is injected from the center injector 6 in the premixed combustion operation region, the injection frequency (injection amount) of the low cetane number fuel decreases and the injection frequency of the high cetane number fuel (Injection amount) increases. As a result, the consumption rate difference ΔC can be reduced.

  In the premixed combustion operation region, the in-cylinder pressure and the in-cylinder temperature decrease as the load (accelerator opening Accp) decreases. Therefore, as shown in FIG. 20, the ECU 16 decreases the load (accelerator opening Accp) in the mixed fuel. The opening degree of the second flow rate adjustment valve 122 may be controlled so that the high cetane number fuel is large and the low cetane number fuel is small. In this case, it is possible to increase the injection frequency of the high cetane fuel while suppressing the decrease in ignitability.

  Furthermore, the ECU 16 adjusts the second flow rate so that the higher the absolute value (= | ΔC |) of the consumption rate difference ΔC is, the larger the amount of high cetane number fuel in the mixed fuel and the smaller the amount of low cetane number fuel. The opening degree of the valve 122 may be controlled. According to such control, even when the absolute value of the difference ΔC in the consumption rate is large, the difference ΔC in the consumption rate is within the allowable range Y before the remaining amount Rl of the low cetane number fuel becomes zero. It becomes easy to converge to.

  By the way, when the injection frequency is changed by the method as described above, the consumption rates Cl and Ch and the remaining amounts Rl and Rh of the low cetane number fuel and the high cetane number fuel become substantially equal. When the remaining amount of fuel becomes zero, the other fuel may remain slightly.

  At that time, if the high cetane number fuel remains, the ECU 16 injects the high cetane number fuel from the center injector 6 and the side injector 7 in the same manner as in the start-up and warm-up operation shown in FIG. In this case, since the ignitability of the premixed gas is increased, the premixed combustion operation region is narrowed, but the operation of the internal combustion engine 1 can be continued.

  On the other hand, when only the low cetane number fuel remains, if premixed combustion is performed only with the low cetane number fuel, there is a possibility that a misfire may occur. Therefore, the ECU 16 injects the low cetane number fuel from the center injector 6. Then, the internal combustion engine 1 is operated by diffusion combustion.

  Specifically, as shown in FIG. 21, the ECU 16 controls the first flow rate adjustment valve 82 so that the first fuel pipe 8 is connected only to the second branch pipe 81 and operates the second fuel pump 14. By prohibiting, low cetane number fuel is injected from the center injector 6.

  At that time, by stopping the cooling of the EGR gas and / or the cooling of the intake air, the in-cylinder temperature and the in-cylinder pressure may be increased as much as possible to improve the ignitability of the low cetane number fuel.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a conceptual diagram which shows the method to discriminate | determine whether the difference (DELTA) C of the consumption rate of a high cetane number fuel and a low cetane number fuel is appropriate. It is a figure which shows the transition of the difference (DELTA) C of the consumption rate when the consumption rate of a low cetane number fuel is forcedly raised. It is a figure which shows the transition of the difference (DELTA) C of the consumption rate when the consumption rate of a high cetane number fuel is forcedly raised. It is a figure which shows the example which cannot converge the difference (DELTA) C of a consumption rate to the tolerance | permissible_range Y. FIG. It is a figure which shows the example which makes the reference value Rbase variable according to the magnitude | size of the difference (DELTA) C of a consumption rate. It is a figure which shows the example which changes the variation | change_quantity of a consumption rate according to the magnitude | size of consumption rate difference (DELTA) C. It is a figure which shows the other example which makes the change amount of a consumption rate variable according to the magnitude | size of consumption rate difference (DELTA) C. It is a figure which shows the example which changes reference value Rbase according to the kind of fuel. It is a figure which shows the control signal input into a center injector and a side injector in a diffusion combustion operation area | region. It is a figure which identifies the diffuse combustion operation area | region and premixed combustion operation area | region of an internal combustion engine. It is a figure which identifies the post injection execution area | region with a high cetane number fuel, and the post injection execution area | region with a low cetane number fuel. It is a figure which shows schematic structure of the internal combustion engine in a 3rd Example. It is a figure which shows schematic structure of the internal combustion engine in a 4th Example. It is a figure which shows the flow of a fuel when an internal combustion engine is in a starting state and a warming-up operation state in a 4th Example. It is a figure which shows the flow of a fuel when an internal combustion engine is in a warming-up completion state in a 4th Example. It is a figure which shows the flow of a fuel when raising the consumption rate of a low cetane number fuel compulsorily in a 4th Example. It is the figure which defined the quantity of the low cetane number fuel injected from a center injector in a diffusion combustion operation area | region. It is a figure which shows the flow of a fuel when raising the consumption rate of a high cetane number fuel compulsorily in a 4th Example. It is the figure which defined the quantity of the high cetane number fuel injected from a side injector in a premixed combustion operation area | region. It is a figure which shows the flow of a fuel when the residual amount of a high cetane number fuel becomes zero.

Explanation of symbols

1... Internal combustion engine 6... Center injector (Diffusion combustion injection valve)
7 ... Side injector (premixed combustion injection valve)
DESCRIPTION OF SYMBOLS 8 ... 1st fuel pipe 9 ... 1st fuel tank 10 ...... 1st fuel pump 11 ...... 1st remaining amount sensor (acquisition means)
12 .... second fuel pipe 13 .... second fuel tank 14 .... second fuel pump 15 .... second remaining amount sensor (acquisition means)
16 .... ECU (injection frequency changing means)
80... First branch pipe 81... Second branch pipe 82... First flow rate adjusting valve 120 ... Third branch pipe 121 ... Fourth branch pipe 122 ... Second Flow control valve

Claims (7)

A plurality of fuel injection valves that inject different types of fuel;
Obtaining means for obtaining consumption of the plurality of types of fuel;
An injection frequency changing means for increasing the injection frequency of fuel with less consumption when a difference of a predetermined reference value or more occurs in the consumption of the plurality of types of fuel;
Equipped with a,
The heterogeneous fuel injection control device for an internal combustion engine, wherein the injection frequency changing means changes a change start timing of the injection frequency in accordance with a type of fuel with a small amount of consumption . 2. The injection frequency changing means according to claim 1, wherein the cetane number of the fuel with low consumption is lower than the cetane number of the fuel with high consumption when the cetane number of the fuel with low consumption is lower than the cetane number of the fuel with high consumption. A fuel injection control device for an internal combustion engine characterized in that the change start timing of the injection frequency is advanced as compared with a case where the value is higher than the value. 3. The heterogeneous fuel injection control device for an internal combustion engine according to claim 1, wherein the injection frequency changing means increases the injection frequency of fuel with less consumption as the difference in consumption increases. 4. The heterogeneous fuel injection control device for an internal combustion engine according to claim 1, wherein the injection frequency changing means advances the change start timing of the injection frequency as the difference in consumption increases. 5. The internal combustion engine according to claim 1, wherein the injection frequency changing means increases post-injection frequency of fuel with low consumption by performing post injection using fuel with low consumption. Heterogeneous fuel injection control device. 6. The injection frequency changing means according to claim 1, wherein the injection frequency changing means has a low consumption amount by injecting a fuel with a low consumption amount when the operating state of the internal combustion engine is in a fuel injection region with a high consumption amount. A fuel injection control apparatus for an internal combustion engine, characterized by increasing a fuel injection frequency. In Claim 6, the plurality of types of fuels are two types of fuels having different cetane numbers,
  When the consumption of high cetane fuel is less than that of low cetane fuel, the injection frequency changing means is
The high cetane number fuel is injected instead of the low cetane number fuel when the operating state of the internal combustion engine is in the low cetane number fuel injection region and in the low rotation operation state and / or the low load operation state. A heterogeneous fuel injection control device for an internal combustion engine characterized by increasing the injection frequency of a valence fuel.

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