JP4452637B2 - Fuel injection control device for diesel engine - Google Patents

Description

  The present invention relates to a fuel injection control device for a diesel engine in which pilot injection is performed.

Conventionally, various fuel injection control devices for reducing combustion noise of diesel engines have been proposed.
For example, in the apparatus described in Patent Document 1, a small amount of fuel is injected prior to main injection, which is fuel injection for obtaining engine output, and by performing this small amount of fuel injection, so-called pilot injection. The combustion noise of the diesel engine is reduced.

The fuel injected by the pilot injection has the effect of reducing the combustion speed of the fuel injected by the main injection performed thereafter, thereby suppressing the rapid combustion of the fuel injected by the main injection, and the combustion noise, etc. Is reduced.
JP 2001-152948 A

  By the way, when the pilot injection is performed, the combustion of the fuel injected in the main injection becomes slow, so that the increase in the in-cylinder pressure etc. also slows down, and the combustion efficiency decreases accordingly. Therefore, although the combustion noise can be suppressed when pilot injection is performed, there is a problem that the fuel consumption rate (fuel consumption per unit output / unit time) is deteriorated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection control device that can suitably suppress deterioration of the fuel consumption rate of a diesel engine in which pilot injection is performed. is there.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, in the fuel injection control device for a diesel engine in which pilot injection is performed, the pilot is obtained from the first pilot injection amount map based on the fact that the vehicle interior noise of the vehicle in which the diesel engine is mounted is small The injection amount is calculated, and the pilot injection amount is calculated from the second pilot injection amount map in which the pilot injection amount is reduced from the first pilot injection amount map based on the fact that the vehicle interior noise is large. The gist.

When the vehicle interior noise of a vehicle equipped with a diesel engine is large, the vehicle interior noise becomes a masking sound and masks the combustion noise. In such a case, even if the pilot injection amount is reduced, the combustion noise becomes difficult to hear. . Therefore, in the above configuration, when the vehicle interior noise is large, the pilot injection amount is reduced compared to when the vehicle interior noise is small. Therefore, the deterioration of the combustion efficiency of the main injection performed after the pilot injection is suppressed, and according to the configuration, the deterioration of the fuel consumption rate can be suitably suppressed for the diesel engine in which the pilot injection is performed. become able to.
According to a second aspect of the present invention, in the fuel injection control device for a diesel engine according to the first aspect, in the first pilot injection amount map, the pilot injection amount in the high rotation high load operation region is a pilot other than the same region. The gist is that it is set smaller than the injection amount.
According to a third aspect of the present invention, in the fuel injection control device for a diesel engine according to the first or second aspect, in the second pilot injection amount map, an engine operation region excluding a low rotation region and a medium rotation high load region. The gist of the present invention is that the pilot injection amount is set smaller than the pilot injection amount in the low rotation region and the medium rotation high load region.

When reducing the pilot injection amount, as described in the fourth aspect of the invention, the diesel injection is performed by adopting a configuration in which the pilot injection is stopped when the vehicle interior noise is large. The engine can be reliably prevented from deteriorating its fuel consumption rate.

According to a fifth aspect of the present invention, in the fuel injection control device for a diesel engine according to any one of the first to fourth aspects, when the reduction ratio changed by the transmission of the vehicle is equal to or less than a predetermined value. The gist is to determine that the vehicle interior noise is large.

  Vehicle interior noise such as road noise and wind noise increases as the vehicle speed increases. Therefore, in the above configuration, when the reduction ratio is less than or equal to a predetermined value, that is, when the transmission gear stage is set to a high gear stage, and thus it can be considered that the vehicle speed is high, It is determined that the vehicle interior noise is high. As described above, according to the same configuration, it is possible to appropriately determine whether or not the vehicle interior noise is large, so that the pilot injection amount can be appropriately reduced based on the vehicle interior noise. Become. In addition, as an aspect which determines whether the said reduction ratio is below a predetermined value, the following are mentioned, for example. First, when the transmission is an automatic transmission, it can be determined that the reduction ratio is equal to or less than a predetermined value when the gear stage indicated by the shift command value to the automatic transmission is high. In addition, when the transmission is a manual transmission, the position of the shift lever operated by the driver is detected, and when the gear stage indicated by the detected value is high, the reduction ratio is a predetermined value. It can be determined that:

Further, according to the sixth aspect of the present invention, whether or not the vehicle interior noise is large is properly determined by a configuration in which it is determined that the vehicle interior noise is large when the vehicle speed of the vehicle is equal to or higher than a predetermined value. Even with this configuration, the pilot injection amount can be appropriately reduced based on the vehicle interior noise.

  Hereinafter, an embodiment in which a fuel injection control device for a diesel engine according to the present invention is applied to an accumulator diesel engine (common rail diesel engine) mounted on a vehicle will be described with reference to FIGS. .

In FIG. 1, the diesel engine 11 in this embodiment and its periphery structure are shown.
The diesel engine 11 has a plurality of cylinders 12. The diesel engine 11 is provided with injectors 13 corresponding to the combustion chambers of the cylinders 12, and fuel is injected from the injectors 13 into the combustion chambers. The injector 13 includes an electromagnetic valve 14 for injection control, and fuel injection by the injector 13 is controlled based on the opening / closing operation of the electromagnetic valve 14. The fuel injected from the injector 13 is combusted, whereby the crankshaft that is the output shaft is rotated.

  A five-speed automatic transmission 50 is connected to the crankshaft. The rotation of the crankshaft is changed by the automatic transmission 50, and the rotation after the change is transmitted to the drive wheels.

  Each injector 13 is connected to a common rail 15. The common rail 15 is connected to a discharge port 18a of a supply pump 18 via a supply pipe 17 provided with a check valve 16.

  The suction port 18 b of the supply pump 18 is connected to the fuel tank 21 via the filter 19. Further, the return port 18 c of the supply pump 18 and the return port 14 a of the electromagnetic valve 14 are both connected to the fuel tank 21 via the return pipe 22.

  The supply pump 18 includes a plunger that reciprocates in synchronization with the rotation of the crankshaft of the diesel engine 11. The supply pump 18 pressurizes the fuel in the supply pump 18 by the plunger, and discharges the pressurized fuel to the discharge port 18a. To the common rail 15. The fuel pumping amount of the supply pump 18 is adjusted based on the opening / closing operation of the pressure control valve 23 provided in the vicinity of the discharge port 18a.

  The diesel engine 11 is provided with various sensors for detecting the engine operating state. For example, an accelerator sensor 31 is provided in the vicinity of the accelerator pedal 24 for detecting the amount of depression of the accelerator pedal 24 (accelerator operation amount ACCP). The common rail 15 is provided with a fuel pressure sensor 32 that detects the fuel pressure PC inside the common rail 15. A vehicle speed sensor 33 for detecting the vehicle speed SPD is provided on the automatic transmission 50 or on the wheels of the vehicle. Further, the crank angle sensor 34 provided in the vicinity of the crankshaft detects the rotation angle of the crankshaft, that is, the crank angle, and the engine speed NE is calculated based on this detection signal. Further, a cam angle sensor 35 is provided in the vicinity of the camshaft that rotates in synchronization with the rotation of the crankshaft. Cylinder discrimination is performed based on the detection signal of the cam angle sensor 35.

  Output signals from these sensors 31 to 35 are input to the electronic control unit 41 of the diesel engine 11. The electronic control unit 41 includes a CPU (Central Processing Unit), a memory, an input / output circuit, a drive circuit, and the like, and various engines based on the engine operating state detected by the sensors 31 to 35. Execute control etc.

  For example, the electronic control unit 41 performs automatic shift control of the automatic transmission 50. In this automatic shift control, a shift command value SHI is calculated based on the engine speed NE, the vehicle speed SPD, and the like. The shift command value SHI is a value corresponding to the gear position in the automatic transmission 50. For example, when the shift command value SHI is set to “1st speed”, the gear position in the automatic transmission 50 is set to “1st speed”. The transmission mechanism in the automatic transmission 50 is controlled so that Then, by changing the gear stage in the automatic transmission 50 to the gear stage indicated by the shift command value SHI, the rotation of the crankshaft is reduced or increased at a reduction ratio according to the running state of the vehicle. The

  Further, fuel injection control is performed by the electronic control device 41. In this fuel injection control, basically, a fuel injection amount (hereinafter referred to as a total fuel injection amount Qfin) is calculated based on the accelerator operation amount ACCP, the engine speed NE, and the like, and the total fuel injection amount Qfin is set at an appropriate time. The valve opening timing and the valve opening time of the electromagnetic valve 14 are controlled so that the injector 13 can inject fuel from the injector 13.

  Here, in the diesel engine 11 in this embodiment, pilot injection is performed in order to reduce the combustion noise of fuel. The pilot injection is a small amount of fuel injection performed prior to main injection, which is fuel injection for obtaining engine output, and the fuel injected in this pilot injection is the amount of fuel injected in the subsequent main injection. It has the effect of reducing the burning rate. That is, since there is an effect of suppressing rapid combustion of the fuel injected by the main injection, the combustion noise is thereby reduced. Moreover, since the combustion temperature of the fuel injected by main injection also falls by the same effect, production | generation of NOx (nitrogen oxide) is also suppressed by this.

  By the way, when the pilot injection is performed, the combustion of the fuel injected in the main injection becomes slow, so that the increase in the in-cylinder pressure etc. becomes slow, and the combustion efficiency is lowered accordingly. Therefore, when pilot injection is performed, combustion noise can be suppressed, but there is a problem that the fuel consumption rate (unit output / fuel consumption per unit time) deteriorates.

  Here, when the vehicle interior noise is large and the vehicle interior noise is large, the vehicle interior noise becomes a masking sound and the fuel combustion noise is masked. Even if the pilot injection amount is reduced, the combustion noise becomes difficult to hear. Therefore, the pilot injection amount can be reduced when the vehicle interior noise is high, and the deterioration of the fuel consumption rate of the diesel engine 11 in which the pilot injection is performed can be suppressed by such reduction.

  Therefore, in the present embodiment, as shown in FIG. 2, the pilot injection amount setting map for setting the pilot injection amount, as shown in FIG. A second pilot injection amount setting map MAP2 whose main purpose is to suppress deterioration of the consumption rate is prepared. These maps are switched according to the magnitude of the vehicle interior noise.

  Note that vehicle interior noise such as road noise and wind noise that accompanies the traveling of the vehicle increases as the vehicle speed increases. Therefore, when the reduction ratio changed by the automatic transmission 50 is small below a predetermined value, that is, the gear stage of the automatic transmission 50 is set to a high gear stage and the vehicle speed of the vehicle is high. When it is possible, it can be determined that the vehicle interior noise is large.

  Therefore, in the present embodiment, it is determined whether or not the vehicle interior noise is large based on the shift command value SHI. When it is determined that the vehicle interior noise is low, the first pilot injection amount setting map MAP1 is selected because the combustion noise masking effect due to vehicle interior noise cannot be expected. On the other hand, when it is determined that the vehicle interior noise is high, the second pilot injection amount setting map MAP2 is selected because a combustion noise masking effect due to vehicle interior noise can be expected.

  FIG. 3 shows a processing procedure for setting the pilot injection amount in the present embodiment. The pilot injection amount setting process is repeatedly executed by the electronic control device 41 every predetermined period.

When this process is started, first, the total fuel injection amount Qfin, the engine speed NE, and the shift command value SHI are read (S100).
Next, it is determined whether or not the shift command value SHI is equal to or greater than a predetermined value (S110). This predetermined value is set when the reduction ratio changed by the automatic transmission 50 is smaller than a predetermined value, that is, the gear stage of the automatic transmission 50 is set to a high gear stage, and the vehicle speed is high. For example, in the present embodiment, “fourth speed” is set.

  When the shift command value SHI is smaller than the predetermined value (S110: NO), in this embodiment, the shift command value SHI is any one of “neutral”, “first speed”, “second speed”, and “third speed”. If it is, the gear stage of the automatic transmission 50 is low, that is, the reduction ratio is large, and the vehicle speed is low. Therefore, it is determined that the vehicle interior noise is low. Therefore, the first pilot injection amount setting map MAP1 is selected (S120).

  In the first pilot injection amount setting map, various pilot injection amounts Qpl that are optimized to reduce the combustion noise that is easily heard when the vehicle speed is low are set. Note that if pilot injection is performed when the engine operating state is in a high rotation and high load state, it is easy to cause an increase in smoke concentration or a decrease in engine output. Therefore, the pilot injection amount in the region corresponding to such an operating state Qpl is set to “0”. Therefore, when the shift command value SHI is lower than “fourth speed”, the pilot injection is stopped and only the main injection is executed when the engine operating state is in the high rotation high load state.

  When the first pilot injection amount setting map MAP1 is selected in this way, an appropriate pilot injection amount Qpl corresponding to when the vehicle interior noise is low is set based on the total fuel injection amount Qfin and the engine speed NE (S130). This process is once terminated.

  On the other hand, when it is determined in step S110 that the shift command value SHI is greater than or equal to a predetermined value (S110: YES), in this embodiment, the shift command value SHI is either “4th speed” or “5th speed”. In this case, since the gear stage of the automatic transmission 50 is high, that is, the speed reduction ratio is small and the vehicle speed is high, it is determined that the vehicle interior noise is high. Therefore, the second pilot injection amount setting map MAP2 is selected (S140).

  The pilot injection amount Qpl set in the second pilot injection amount setting map MAP2 is smaller than the pilot injection amount Qpl set in the first pilot injection amount setting map MAP1. More specifically, the pilot injection amount Qpl is basically set to “0” in a region excluding the low rotation region and the medium rotation high load region. In other words, the pilot injection amount Qpl in the region where the vehicle speed is high and the combustion noise is masked by the vehicle interior noise is set to “0”. For the above reason, also in the second pilot injection amount setting map MAP2, the pilot injection amount Qpl when the engine operating state is in the high rotation high load state is set to “0”. Therefore, when the shift command value SHI is “fourth speed” or higher, the pilot injection is stopped when the combustion noise is masked by the vehicle interior noise and when the engine operating state is in the high rotation high load state, Only main injection is performed.

  When the second pilot injection amount setting map MAP2 is selected in this way, an appropriate pilot injection amount Qpl corresponding to when the vehicle interior noise is large is set based on the total fuel injection amount Qfin and the engine speed NE (S150). This process is once terminated.

  When the pilot injection amount Qpl is set in this way, the final pilot injection amount is calculated by, for example, appropriately correcting thereafter, and the opening / closing operation of the solenoid valve 14 to inject the pilot injection amount at an appropriate time Is controlled.

FIG. 4 shows an example of a setting mode of the pilot injection amount Qpl by the pilot injection amount setting process.
As shown in FIG. 4, when the vehicle starts traveling by the driver's accelerator operation, the engine rotational speed NE and the vehicle speed SPD increase, and the engine rotational speed NE and the vehicle speed SPD are within a predetermined range (so-called shift). When the range is entered, the gear stage of the automatic transmission 50 is shifted up in the order of “first speed” → “second speed” → “third speed” based on the shift command value SHI. Then, at time t1 when the vehicle speed SPD has increased to some extent, the vehicle is shifted up from “3rd speed” to “4th speed”. Although not shown in FIG. 4, when the vehicle speed SPD is further increased, the gear stage of the automatic transmission 50 is shifted up to “5th speed”.

  In FIG. 4, when the gear stage of the automatic transmission 50 is “third speed” or less (before time t1), the pilot injection amount Qpl is set based on the first pilot injection amount setting map MAP1. The combustion noise of the fuel is reduced.

  On the other hand, when the gear stage of the automatic transmission 50 is “fourth speed” or higher (after time t1), the pilot injection amount Qpl is set based on the second pilot injection amount setting map MAP2. Basically, the injection amount is set to “0”. That is, the execution of pilot injection is stopped and only the main injection is executed. When the pilot injection is stopped in this way, the combustion speed of the fuel injected in the main injection is increased and the combustion efficiency is improved. Therefore, the fuel consumption rate is always compared with the case of performing the pilot injection. Deterioration is suppressed.

  Note that when the gear stage of the automatic transmission 50 is “fourth speed” or higher, the vehicle speed SPD is increased to some extent, and the vehicle interior noise is increased to some extent. Therefore, the combustion noise of the fuel is masked by the vehicle interior noise, and even if the pilot injection is stopped, the combustion noise becomes difficult for the driver to hear.

As described above, according to the present embodiment, the following effects can be obtained.
(1) In the diesel engine 11 in which the pilot injection is performed, when the vehicle interior noise of the vehicle in which the diesel engine 11 is mounted is large, the pilot injection amount at the time of executing the pilot injection is larger than when the vehicle interior noise is small. Qpl is reduced. Therefore, deterioration of the combustion efficiency of main injection performed after pilot injection is suppressed. Accordingly, it is possible to suppress the deterioration of the fuel consumption rate of the diesel engine 11 in which pilot injection is performed.

  (2) When reducing the pilot injection amount, when the vehicle interior noise is large, the pilot injection amount Qpl at the time of executing the pilot injection is set to “0”, that is, the pilot injection is stopped. For this reason, the deterioration of the fuel consumption rate can be reliably suppressed.

  (3) When the reduction ratio changed by the automatic transmission 50 is less than or equal to a predetermined value, more specifically, when the shift command value SHI is "fourth speed" or more, the vehicle speed is high and the vehicle interior noise Is determined to be larger. Therefore, it is possible to appropriately determine whether or not the vehicle interior noise is large, and thus it is possible to appropriately reduce the pilot injection amount performed based on the vehicle interior noise.

  (4) The pilot injection amount Qpl is set based on a map (first and second pilot injection amount setting maps) that is switched according to vehicle interior noise. Therefore, it is possible to easily reduce the pilot injection amount Qpl in accordance with the characteristics of vehicle interior noise.

In addition, the said embodiment can also be changed and implemented as follows.
The setting mode of the pilot injection amount Qpl in the first and second pilot injection amount setting maps is an example.

  Further, in order to reduce the pilot injection amount Qpl when the vehicle interior noise is large to be less than the pilot injection amount Qpl when the vehicle interior noise is low, the pilot injection amount Qpl is “0” in the second pilot injection amount setting map. The area that becomes is set. However, it is not always necessary to set “0” when the pilot injection amount is reduced. The pilot injection amount Qpl set when the vehicle interior noise is large is larger than the pilot injection amount Qpl set when the vehicle interior noise is low. At least the weight should be reduced.

  In short, when the vehicle interior noise is large, the pilot injection amount may be reduced compared to when the vehicle interior noise is small. If the pilot injection amount is set in such a manner, the deterioration of the combustion efficiency of the main injection performed after the pilot injection can be suppressed, so that the same effect as the above embodiment can be obtained. it can.

  In the above embodiment, the pilot injection amount setting map is switched in order to reduce the pilot injection amount when the vehicle interior noise is large. In addition, the pilot injection amount Qpl is set based on the first pilot injection amount setting map, and the set pilot injection amount Qpl is reduced and corrected by a correction coefficient set as appropriate. Then, the pilot injection amount that has been corrected for reduction may be set as the pilot injection amount when the vehicle interior noise is large.

  In the above embodiment, it is determined based on the shift command value SHI, in other words, whether or not the vehicle interior noise is large based on the gear reduction ratio changed by the automatic transmission 50. In addition, when the vehicle speed SPD of the vehicle is equal to or higher than a predetermined value, it may be determined that the vehicle interior noise is large. Also in this case, it is possible to appropriately determine whether or not the vehicle interior noise is large, and it is possible to appropriately reduce the pilot injection amount performed based on the vehicle interior noise.

In addition, the vehicle interior noise may be directly detected, and it may be determined whether the vehicle interior noise is large based on the detected value.
The present invention can be similarly applied even when the shift stage of the automatic transmission is a shift stage different from the above embodiment. In this case, the predetermined value to be compared with the shift command value SHI in step S110 may be appropriately changed according to the setting mode as described above.

  The present invention can be similarly applied even if the automatic transmission 50 is a continuously variable transmission. In this case, when the speed reduction ratio indicated by the shift command value SHI is equal to or less than the predetermined value, it is determined that the vehicle interior noise is large, and the second pilot injection amount setting map MAP2 as described above is selected. That's fine. Note that the predetermined value in this case is set to a value at which it can be determined that the speed reduction ratio changed by the continuously variable transmission is smaller than the predetermined value and the vehicle speed is high.

  In the above embodiment, the transmission is an automatic transmission whose speed is controlled by a control device. In addition, the present invention can be similarly applied to a manual transmission in which the gear in the transmission is changed by the driver. In this case, for example, the position of the shift lever operated by the driver is detected, and the detected value is set as the shift command value SHI. Similarly to the above-described embodiment, when the gear stage indicated by the shift command value SHI is high, it is determined that the reduction ratio of the transmission is not more than a predetermined value, that is, the vehicle speed is high and the vehicle interior noise is large. do it.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the structure of the engine to which this is applied about one Embodiment which actualized the fuel-injection control apparatus of the diesel engine concerning this invention. The conceptual diagram which shows the pilot injection amount setting map in the embodiment. The flowchart which shows the procedure about the pilot injection amount setting process in the embodiment. The time chart which shows the example about the setting mode of the pilot injection amount by a pilot injection amount setting process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Diesel engine, 12 ... Cylinder, 13 ... Injector, 14 ... Electromagnetic valve, 14a ... Return port, 15 ... Common rail, 16 ... Check valve, 17 ... Supply piping, 18 ... Supply pump, 18a ... Discharge port, 18b ... Suction port, 18c ... return port, 19 ... filter, 21 ... fuel tank, 22 ... return pipe, 23 ... pressure control valve, 24 ... accelerator pedal, 31 ... accelerator sensor, 32 ... fuel pressure sensor, 33 ... vehicle speed sensor, 34 ... Crank angle sensor, 35 ... cam angle sensor, 41 ... electronic control unit, 50 ... automatic transmission.

Claims (6)

In a fuel injection control device for a diesel engine in which pilot injection is performed,
The diesel engine pilot injection quantity is calculated from the first pilot injection amount map based on a small particular interior noise of a vehicle equipped with, taking the same car interior noise is large in particular the first pilot injection amount based A fuel injection control device for a diesel engine, wherein the pilot injection amount is calculated from a second pilot injection amount map in which the pilot injection amount is reduced from the map. The fuel injection control device for a diesel engine according to claim 1,
In the first pilot injection amount map, the pilot injection amount in the high rotation and high load operation region is set to be smaller than the pilot injection amount in other regions.
A fuel injection control device for a diesel engine. The fuel injection control device for a diesel engine according to claim 1 or 2,
In the second pilot injection amount map, the pilot injection amount in the engine operation region excluding the low rotation region and the medium rotation high load region is set smaller than the pilot injection amount in the low rotation region and the medium rotation high load region.
A fuel injection control device for a diesel engine. In the diesel engine fuel injection control apparatus according to any one of claims 1 to 3,
The pilot injection is stopped when the vehicle interior noise is high
A fuel injection control device for a diesel engine. In the diesel engine fuel injection control apparatus according to any one of claims 1 to 4,
It is determined that the vehicle interior noise is large when a reduction ratio changed by the transmission of the vehicle is equal to or less than a predetermined value.
A fuel injection control device for a diesel engine. In the diesel engine fuel injection control apparatus according to any one of claims 1 to 4,
It is determined that the vehicle interior noise is large when the vehicle speed of the vehicle is equal to or higher than a predetermined value.
A fuel injection control device for a diesel engine.

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