JP6424687B2 - Control system of diesel engine - Google Patents

Description

  The present invention relates to a control device that controls a diesel engine.

  Heretofore, as a technology relating to the property of fuel used in a diesel engine, various devices for detecting cetane number with high accuracy have been proposed in order to execute combustion control based on the cetane number of the fuel. For example, the fuel property detection device described in Patent Document 1 executes specific injection so as to respectively inject two predetermined levels of injection amounts, and calculates the change sensitivity. Then, the cetane number of the fuel is detected using the correspondence between the change sensitivity and the cetane number of the fuel. The change sensitivity represents the ratio of the change physical amount to the change amount which is the change amount of the injection amount of two levels, and the change physical amount can identify the combustion state corresponding to the change amount of the injection amount of the two levels. It is a change amount of a specific amount that is a physical amount.

JP, 2009-144528, A

  The cetane number of the fuel is one indicator of fuel properties, but there are also fuel properties that can not be distinguished from the cetane number. Therefore, there is a possibility that it is not possible to suppress the increase of emission such as cooling loss and soot by concentration of the combustion region in the cylinder of the internal combustion engine in the vicinity of the wall surface of the combustion chamber only by executing the combustion control according to the cetane number. .

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a control device of a diesel engine capable of realizing appropriate combustion control even when there is fuel property variation. .

  Hereinafter, a means for solving the above-mentioned subject, and its operation effect are explained.

  The control device of the present invention controls a diesel engine (10) including a fuel injection valve (17) for injecting fuel into a combustion chamber (11b). The control device (40) acquires the dynamic viscosity acquired by the kinetic viscosity acquired by the kinetic viscosity acquiring unit acquiring the dynamic viscosity of the fuel, the density acquiring unit acquiring the density of the fuel, and the dynamic viscosity acquiring unit from the density acquiring unit Component calculation means for calculating, as fuel component data, the ratio of the amount of carbon contained in the fuel to the amount of hydrogen contained in the fuel or the parameter based on the calculated density, and the fuel component data calculated by the component calculation means And control means for performing combustion control on the combustion of the fuel injected from the fuel injection valve into the combustion chamber.

  The inventor noted that the ratio (C / H) of the amount of carbon and the amount of hydrogen contained in the fuel is an index that accurately represents the combustibility of the fuel. In this case, for example, as the C / H is larger, the number of carbons relative to the number of hydrogen increases, which makes it difficult to burn. The inventor also noted that C / H has a high correlation with the dynamic viscosity and density of the fuel, which are parameters that can be acquired in the engine system. Then, based on the dynamic viscosity and the density of the fuel, the ratio of the amount of carbon contained in the fuel to the amount of hydrogen or the parameter correlating to that is calculated as the fuel component data, and the combustion control is carried out based on the fuel component data It was composition. In this case, appropriate combustion control can be performed while taking into consideration the combustibility of the fuel.

The schematic diagram which shows a diesel engine and its periphery structure. A distribution chart showing distribution of fuel to fuel density and cetane number. The figure which shows the boiling point of the single composition of a hydrocarbon. The figure which shows the relationship between dynamic viscosity and T50. The figure which shows distribution of a fuel by making a fuel density and T50 into a parameter. The figure which shows the relationship between the amount of soot and C / H. The flowchart which shows the processing procedure of combustion control. The flowchart which shows the process sequence of the combustion control in 2nd Embodiment. The flowchart which shows the process sequence of the combustion control in 3rd Embodiment. The figure which shows the relationship between lower calorific value and C / H. The functional block diagram which shows the outline | summary of combustion state feedback control.

  Hereinafter, each embodiment which materialized the control device which controls the diesel engine for vehicles is described. In addition, in the following each embodiment, the same code | symbol is attached | subjected to the mutually same or equal part in the figure, and the description is used about the part of the same code | symbol.

First Embodiment
First, an outline of an engine 10 which is a diesel engine will be described with reference to FIG. The engine 10 is, for example, an in-line four-cylinder diesel engine, and only one cylinder is shown in FIG. As shown in the figure, the engine 10 includes a cylinder block 11, a piston 12, a cylinder head 13, an intake passage 14, an exhaust passage 15, an intake valve 16, an injector 17, an exhaust valve 18, a VVT 21, an EGR device 26, etc. There is.

  Four cylinders 11 a are formed in the cylinder block 11. A piston 12 is accommodated in each of the cylinders 11 a so as to be capable of reciprocating. The cylinder head 13 is assembled to the cylinder block 11. A cavity (recess) is formed on the upper surface of the piston 12, and the combustion chamber 11b is formed by the cavity.

  The intake passage 14 is formed as a passage in the intake manifold and the cylinder head 13 and is connected to each cylinder 11 a. The rotation of the crankshaft (not shown) of the engine 10 causes the camshafts 19A and 19B to rotate. Each intake valve 16 is driven based on the rotation of the camshaft 19A, and in response to the drive of each intake valve 16, intake air flows into the combustion chamber 11b. The VVT 21 (variable valve timing device) makes the open / close timing of the intake valve 16 variable by adjusting the rotational phase of the crankshaft and the camshaft 19A.

  The exhaust passage 15 is formed as an exhaust manifold and a passage in the cylinder head 13, and is connected to each cylinder 11a. Each exhaust valve 18 is driven based on the rotation of the camshaft 19B, and the exhaust is discharged from the combustion chamber 11b according to the drive of each exhaust valve 18.

  The common rail 20 (pressure accumulation container) holds the fuel in the pressure accumulation state. The fuel is pressurized to a high pressure state by a fuel pump (not shown) and pumped to the common rail 20. The injector 17 (fuel injection valve) injects the fuel held in the pressure-accumulated state in the common rail 20 into the combustion chamber 11b. The injector 17 is a known electromagnetic or piezo driven valve that controls the opening period by controlling the fuel pressure of the control chamber that applies pressure to the nozzle needle in the valve closing direction. The valve opening period is controlled by the energization time to the electromagnetic drive type or piezo drive type actuator, and the injection amount to be injected becomes larger as the valve opening period of the injector 17 becomes longer.

  The EGR device 26 (exhaust gas recirculation device) includes an EGR passage 27 and an EGR valve 28. The EGR passage 27 connects the exhaust passage 15 and the intake passage 14. The EGR passage 27 is provided with an EGR valve 28 for opening and closing the EGR passage 27. The EGR device 26 introduces a part of the exhaust gas in the exhaust passage 15 into the intake passage 14 in accordance with the opening degree of the EGR valve 28.

  Air is taken into the cylinder 11 a through the intake passage 14 in the intake stroke of the engine 10, and the air is compressed by the piston 12 in the compression stroke. The fuel is injected into the cylinder 11a (in the combustion chamber 11b) by the injector 17 near the compression top dead center, and the fuel injected in the combustion stroke is self-ignited and burned. Exhaust gas in the cylinder 11 a is exhausted through the exhaust passage 15 in the exhaust stroke. A part of the exhaust gas in the exhaust passage 15 is introduced into the intake air in the intake passage 14 by the EGR device 26.

  The engine 10 is provided with an in-cylinder pressure sensor 31. The in-cylinder pressure sensor 31 detects the pressure in the cylinder 11 a (in-cylinder pressure). The in-cylinder pressure sensor 31 does not have to be installed in all the cylinders 11a, and may be set in at least one cylinder 11a. A fuel density sensor 32, a dynamic viscosity sensor 33, and a fuel amount sensor 34 are provided in a fuel tank (not shown) of the engine 10. The fuel density sensor 32 detects the density of the fuel supplied to the injector 17. The fuel density sensor 32 detects the density of the fuel based on, for example, the natural oscillation period measurement method. The kinematic viscosity sensor 33 is, for example, a capillary viscometer or a kinematic viscometer based on a thin wire heating method, and detects the kinematic viscosity of the fuel in the fuel tank. The fuel amount sensor 34 detects the amount of fuel in the fuel tank. The fuel density sensor 32 and the dynamic viscosity sensor 33 each include a heater, and detect the density and the dynamic viscosity of the fuel while heating the fuel to a predetermined temperature by the heater.

  The ECU (Electric Control Unit) 40 is a known microcomputer including a CPU, a ROM, a RAM, an I / O, a storage device 41 and the like, and corresponds to a control device that controls the engine 10. The ECU 40 is connected to a notification device 50 that notifies a driver or the like of the occurrence of an abnormality in the vehicle. The notification device 50 is, for example, a speaker or a display provided in a vehicle compartment.

  The ECU 40 detects injectors 17, VVT 21 based on detection values of various sensors such as a crank angle sensor, a coolant temperature sensor, an accelerator opening sensor, an in-cylinder pressure sensor 31, a fuel density sensor 32, a dynamic viscosity sensor 33, and a fuel amount sensor 34. , Controls the EGR device 26 and the like. Specifically, the control states of the injectors 17, the VVT 21 and the EGR device 26 are adapted in advance according to the operating state of the engine 10 so that the fuel combustion state becomes optimal assuming a fuel of standard properties. . The ECU 40 controls the respective devices so as to be in the adapted control state (normal combustion control) based on the detection values of various sensors. The ECU 40 uses the injector 17 to perform multistage injection including at least pilot injection and main injection.

  Further, the ECU 40 implements the respective functions of a dynamic viscosity acquisition unit, a density acquisition unit, a component calculation unit, a control unit, and a soot amount determination unit by the CPU executing various programs stored in the ROM.

  FIG. 2 is a distribution chart showing the distribution of fuel with respect to fuel density and cetane number. As shown in the figure, the fuel used for the engine 10 is distributed mainly to the kerosene side and the A heavy oil side, mainly in the vicinity of JIS No. 2 light oil classified into No. 2 according to the JIS K2204 standard. As it approaches kerosene, it becomes a light fuel containing a lot of light components, and as it approaches A fuel oil, it becomes a heavy fuel containing a lot of heavy components. The fuel density decreases as the content of the light components increases, and the fuel density increases as the content of the heavy components increases. In addition, the cetane number decreases as approaching to kerosene from JIS No. 2 light oil, and the cetane number decreases as approaching to heavy oil A from JIS No. 2 light oil.

  That is, even if the cetane number is the same value, it may correspond to light fuel or heavy fuel. Light fuel has poor ignitability, but soot is less likely to be generated during combustion. Heavy fuels, like light fuels, have poor ignitability, and in addition, they tend to generate soot during combustion. Soot is carbon-based fine particles generated by incomplete combustion caused by oxygen deficiency at the time of combustion. Therefore, although cetane number is an index that represents ignitability, it is insufficient as an index that accurately represents combustibility. Therefore, even if the fuel injection amount, the opening / closing timing of the intake valve 16, and the EGR amount (exhaust gas recirculation amount) are suppressed according to the cetane number, there is a possibility that fuel combustion can not be appropriately controlled.

  Here, the inventor has found that the ratio of the amount of carbon to the amount of hydrogen contained in the fuel, more specifically, the ratio of the number of carbons to the number of hydrogen of the molecules contained in the fuel (hereinafter referred to as C / H) We focused on the fact that it is an indicator that accurately represents That is, as the C / H is larger, the number of carbons relative to the number of hydrogens is increased, which makes it difficult to burn. For example, if the straight chain of molecules contained in the fuel becomes short, the proportion of side chain components increases. As the proportion of side chain components increases, the number of hydrogens decreases relatively, and C / H increases. So, in this embodiment, combustion control is performed based on C / H of a fuel. C / H may be the ratio of carbon mass to hydrogen mass.

  Moreover, the inventor noted that the dynamic viscosity and the density of the fuel have a high correlation with C / H. Then, the kinetic viscosity and the density of the fuel are detected, and C / H is calculated based on the kinetic viscosity and the density.

  In detail, hydrocarbon has a strong correlation between carbon number and boiling point, and the relationship is as shown in FIG. Further, there is a correlation shown in FIG. 4 between the dynamic viscosity of the fuel and T50 (50% volume distillation temperature [° C.]). In this case, according to FIG. 3, it can be confirmed that the boiling point becomes higher as the carbon number is larger, and according to FIG. 4, it can be confirmed that T50 becomes larger as the dynamic viscosity of the fuel is larger. T50 can be regarded as an average boiling point, and referring to the relationship between carbon number and boiling point and the relationship between dynamic viscosity and T50, the smaller the dynamic viscosity, the smaller the carbon number, and the larger the dynamic viscosity, the larger the carbon number Relationship is derived. Therefore, it is possible to calculate the number of carbons based on the kinematic viscosity.

  Moreover, FIG. 5 is a figure which shows distribution of a fuel by making fuel density and T50 into a parameter. In FIG. 5, it can be confirmed that the dispersion of the distribution occurs in both the horizontal axis and the vertical axis due to the dispersion of the fuel. In this case, the variation in the horizontal axis (T50) is mainly due to the carbon number, and the fuel having a large number of carbons is distributed in a region where T50 has a relatively high temperature, and the fuel having a small number of carbons has a relatively large T50. It tends to be distributed in the region where the temperature is low. Also, the variation in the vertical axis (density) is mainly due to the number of hydrogen, fuel with a small number of hydrogen is distributed in a region of relatively high density, and fuel with a large number of hydrogen is relatively low in density It tends to be distributed in the area.

  In FIG. 5, the hydrogen number increases as the fuel density decreases for the same T50 (same carbon number). Therefore, if T50 (carbon number) is known, the number of hydrogen can be calculated based on the fuel density using the correlation between the fuel density and the number of hydrogen. Moreover, since carbon number and hydrogen number are calculated | required as mentioned above, C / H can be calculated by these carbon number and hydrogen number.

  Note that the dynamic viscosity and density of the fuel are information that can be measured by the dynamic viscosity sensor 33 and the fuel density sensor 32 mounted on the vehicle, and acquire the dynamic viscosity and density as needed when using a vehicle such as a car ( It is possible to Therefore, it is possible to calculate the C / H of the fuel in the vehicle.

  FIG. 6 is a diagram showing the relationship between the amount of soot and C / H. The amount of soot is the amount of soot emitted when normal combustion control is performed assuming a fuel of standard characteristics. In FIG. 6, the relationship that the amount of soot becomes larger than the predetermined amount B1 is defined by C / H becoming larger than the predetermined value A1. The soot amount being less than the predetermined amount B1 means that low smoke fuel is used, and the soot amount being larger than the predetermined amount B1 means that high smoke fuel is being used.

  In this embodiment, it is determined based on C / H whether or not the fuel is high smoke fuel, and when it is determined that the fuel is high smoke fuel, smoke suppression control for smoke suppression as combustion control is performed. To carry out.

  Next, the processing procedure of the combustion control of the engine 10 will be described with reference to the flowchart of FIG. This processing procedure is repeatedly performed by the ECU 40 at a predetermined cycle.

  First, it is determined whether an execution condition for detecting fuel properties is satisfied (S10). Specifically, the implementation conditions are that refueling has been performed, the engine rotational speed is constant, the warm-up of the engine 10 is completed, and the temperature of the cooling water becomes higher than a predetermined temperature (for example, 80 ° C.) And so on. Implementation conditions include that fueling is performed and the engine 10 is stable. Whether or not refueling has been performed is determined based on the fuel amount detected by the fuel amount sensor 34, and whether or not the engine rotational speed is constant is determined based on the rotational speed detected by the crank angle sensor Do. Further, it is determined based on the temperature detected by the cooling water temperature sensor whether the temperature of the cooling water is higher than a predetermined temperature. It is determined that refueling has been performed when the fuel amount detected by the fuel amount sensor 34 has increased by a predetermined amount or more compared to the previous detection, and when a predetermined time has elapsed since refueling, or the vehicle travel distance is a predetermined distance. At that time, it is determined that the remaining fuel and the refueling fuel are mixed and the property is stable and is not immediately after refueling.

  When it is determined that the execution condition for detecting the fuel property is not satisfied (S10: NO), the present process is ended. On the other hand, when it is determined that the execution condition for detecting the fuel property is satisfied (S10: YES), the dynamic viscosity detected by the dynamic viscosity sensor 33 is acquired (S11) and the density detected by the fuel density sensor 32 Is acquired (S12).

  Next, C / H is calculated using the kinetic viscosity and the density of the fuel as calculation parameters (S13). At this time, C / H is calculated based on the dynamic viscosity and the density of the fuel, using the map and the correlation function determined based on the above-described relationships of FIGS. The map and the correlation function are determined by adaptation or the like, and are stored in advance in the storage device 41 (the same applies to each relationship described later).

  Subsequently, it is determined whether the C / H calculated in S13 is equal to or more than a predetermined value A1 (S14). If C / H is less than the predetermined value A1 (S14: NO), it is determined that the fuel is low smoke fuel (S15), and normal combustion control is performed (S16). Specifically, based on the detection values of various sensors, the injection amount of fuel by the injector 17, the opening / closing timing of the intake valve 16 by the VVT 21, and the EGR valve by the EGR device 26 are brought into control. Control the opening degree (EGR amount). This is the end of the process.

  On the other hand, if C / H is greater than or equal to the predetermined value A1 (S14: YES), it is determined that the fuel is high smoke fuel (S17), and the normal fuel control is switched to smoke suppression control (S18). finish.

  As the smoke suppression control, processing for increasing the amount of fresh air (amount of oxygen in the combustion chamber) and processing for increasing the injection pressure are performed in order to improve the combustion state when the fuel is burned. Specifically, as the process for increasing the fresh air amount, a process for reducing the opening degree of the EGR valve 28 by the EGR device 26 and a process for increasing the intake pressure by the VVT 21 are performed as compared with the normal combustion control. Further, as a process of increasing the injection pressure, a process of increasing the fuel pressure in the common rail 20 by the fuel pump is performed. In addition, after the main injection of fuel by the injector 17 may be performed after smoke injection as the smoke suppression control. At least one of these processes may be performed. Smoke suppression control continues until combustion control is next switched.

  In addition, when C / H is more than predetermined value A1, while being memorize | stored in the memory | storage device 41 that it is abnormal fuel, using the alerting devices 50, such as a speaker and a display, the warning to the effect that fuel is abnormal is warned. Is carried out (S18).

  According to the first embodiment described above, the following effects can be obtained.

  The inventor noted that the ratio (C / H) of the amount of carbon and the amount of hydrogen contained in the fuel is an index that accurately represents the combustibility of the fuel. In this case, for example, as the C / H is larger, the number of carbons relative to the number of hydrogen increases, which makes it difficult to burn. Moreover, the inventor noted that C / H has a high correlation with the dynamic viscosity and the density of the fuel, which are parameters that can be acquired in the on-vehicle engine system. Then, C / H is calculated based on the dynamic viscosity and density of the fuel, and combustion control is performed based on the C / H. In this case, appropriate combustion control can be performed while taking into consideration the combustibility of the fuel.

  C / H is an index that represents the flammability of the fuel, and according to the C / H, it is possible to determine whether the fuel is a high smoked fuel in which the amount of soot emission tends to increase. Then, when the fuel is determined to be a high smoke fuel, the normal fuel control that assumes a fuel of standard properties is switched to the smoke suppression control that suppresses the discharge amount of soot. As a result, even when the fuel is a high smoked fuel in which the amount of soot emissions is likely to increase, the amount of soot emissions can be suppressed.

  When the fuel C / H is equal to or more than the predetermined value A1, the memory device 41 stores the abnormal fuel in the storage unit 41. Therefore, even if the failure occurs in the engine 10 later, the cause of the failure can be identified. Further, since the warning that the fuel is abnormal is performed by using the notification device 50, the driver can recognize that the fuel is the abnormal fuel and can cope with it.

Second Embodiment
In the second embodiment, the combustion front end position of the fuel in the combustion chamber 11b is calculated based on the C / H of the fuel and the average carbon number (carbon amount), and the combustion control is performed according to the combustion front end position. Hereinafter, the combustion control according to the second embodiment will be described.

  The inventor noted that the position of the combustion front in the combustion chamber 11b is correlated with the C / H of the fuel and the average carbon number. Then, the C / H of the fuel and the average carbon number are calculated, and the combustion tip position is calculated based on them. The combustion tip position is the distance from the tip of the injector to the tip of the combustion region, and the larger the position of the combustion tip, the more the combustion is performed at a position farther from the tip of the injector.

  Here, when the combustion front end position is close to the wall surface of the combustion chamber 11b, the combustion region is concentrated in the vicinity of the wall surface of the combustion chamber 11b, the cooling loss becomes large, and the fuel efficiency may be deteriorated. In addition, when the combustion front end position is close to the injector front end, the combustion region is concentrated in the vicinity of the injector front end, oxygen used when fuel is burned is insufficient, and fuel efficiency may be deteriorated. Therefore, in the second embodiment, the combustion front end position is calculated, and the combustion control is performed so that the combustion front end position falls within a predetermined region.

  In the present embodiment, as the combustion control, the injection pressure is reduced when the combustion tip position is at a position farther than the predetermined region. As a result, the moving speed of the fuel decreases to shorten the reach distance, and the concentration of the combustion region in the vicinity of the wall surface of the combustion chamber 11b is suppressed. Further, the injection pressure is increased when the combustion tip position is closer than the predetermined region. As a result, the moving speed of combustion increases and the reach distance becomes longer, and concentration of the combustion region near the tip of the injector 17 is suppressed. The ECU 40 implements the above functions by the CPU executing a program stored in the ROM.

  Next, the procedure of the combustion control of the engine 10 will be described with reference to the flowchart of FIG. The ECU 40 repeatedly executes this processing procedure at a predetermined cycle.

  First, similarly to S10 to S13 in FIG. 7, the determination of whether or not the execution condition for detecting the fuel property is satisfied, the acquisition of the dynamic viscosity, the acquisition of the fuel density, and the calculation of C / H. (S20 to S23). Thereafter, the average carbon number is calculated based on the dynamic viscosity using a map of the dynamic viscosity and the average carbon number stored in advance (S24).

  Subsequently, combustion is performed based on the C / H of the fuel calculated in S23 and the average carbon number of the fuel calculated in S24 using the map of C / H and average carbon number stored in advance and the position of the combustion tip. The tip position is calculated (S25).

  Subsequently, it is determined whether the combustion tip position calculated in S25 is a position farther from the tip of the injector 17 than the first distance (S26). The first distance is a value that can be determined that the combustion region is concentrated on the wall surface of the combustion chamber 11b when the combustion tip position is farther than this distance. When the combustion tip position is separated from the tip of the injector 17 by more than the first distance (S26: YES), the injection pressure of fuel by the injector 17 is decreased (S27), and the present process is ended.

  On the other hand, when the combustion tip position calculated in S25 is in the range from the tip of the injector 17 to the first distance (S26: NO), the combustion tip position is next closer than the second distance from the tip of the injector 17 It is determined whether it is a position (S28). The second distance is a distance shorter than the first distance, and when the position of the combustion tip is closer than this distance, it can be determined that the combustion region is concentrated in the vicinity of the tip of the injector 17. The predetermined range from the second distance to the first distance corresponds to the predetermined area where the combustion tip position should be present, and if the combustion tip position deviates from the predetermined area, the fuel efficiency may be deteriorated.

  If the combustion tip position is in the range from the tip of the injector 17 to the second distance (S28: YES), the injection pressure of fuel by the injector 17 is increased (S29), and the present process is ended. On the other hand, when the position of the combustion tip is separated from the tip of the injector 17 by more than the second distance (S28: NO), that is, when it falls within the predetermined region, the present process is ended.

  Note that, instead of performing injection pressure control to decrease or increase the injection pressure of fuel in S27 and S29, intake pressure control to increase or decrease intake pressure, which is the pressure of intake air into the combustion chamber 11b, is performed It is also good. That is, when the combustion tip position is separated from the tip of the injector 17 by more than the first distance (S26: YES), the intake pressure is increased. In this case, the combustion front position is closer to the tip of the injector by promoting the combustion by the increase of the fresh air amount. Thereby, concentration of the combustion area in the vicinity of the wall surface of the combustion chamber 11b can be suppressed, and deterioration of fuel consumption can be suppressed. It is also possible to implement both a decrease in injection pressure and an increase in intake pressure at S27.

  In addition, when the combustion tip position is in the range from the tip of the injector 17 to the second distance (S28: YES), the intake pressure is decreased. In this case, the combustion tip position is separated from the tip of the injector because the combustion becomes slow due to the decrease of the fresh air amount. Thus, concentration of the combustion region on the tip of the injector 17 can be suppressed, and deterioration of fuel consumption can be suppressed. In S29, it is also possible to implement both an increase in injection pressure and a decrease in intake pressure.

  In addition, if C / H and an average carbon number are decided, an average hydrogen number will be decided. Therefore, it is also possible to calculate the combustion tip position based on C / H and the average number of hydrogen.

  According to the second embodiment described above, the following effects can be obtained.

  If C / H and the average carbon number which show the flammability of the fuel are used as fuel component data, the combustion in the combustion area using the correlation between the C / H and the average carbon number and the combustion tip position in the combustion area The tip position can be calculated. And, if the combustion tip position does not fall within the predetermined range defined based on the tip position of the injector 17, that is, if it is farther than the first distance or closer than the second distance, the combustion tip position The injection pressure control is performed to reduce or increase the injection pressure of the fuel (or the intake pressure control to increase or decrease the intake pressure) so as to put the fuel pressure in the predetermined range. In this case, since the combustion tip position can be controlled to a desired position, the fuel consumption reduction effect can be obtained.

  Specifically, by reducing the injection pressure (or increasing the intake pressure) when the combustion tip position is farther than the first distance, concentration of the combustion region in the vicinity of the wall surface of the combustion chamber 11b is suppressed, and fuel consumption can be reduced. It is possible to suppress the deterioration. Further, by increasing the injection pressure (or decreasing the intake pressure) when the combustion tip position is closer than the second distance, concentration of the combustion region in the vicinity of the tip of the injector 17 is suppressed, and the fuel consumption is deteriorated. It can be suppressed.

Third Embodiment
In the third embodiment, the ignition delay time in the combustion chamber 11b is calculated based on the C / H of the fuel and the average carbon number (carbon amount), and the ignition delay time of the current fuel and the standard fuel is calculated. An ignition delay change amount which is a difference is calculated, and combustion control is performed according to the ignition delay change amount. The combustion control according to the third embodiment will be described below.

  The processing procedure of the combustion control of the engine 10 will be described with reference to the flowchart of FIG. The ECU 40 repeatedly executes this processing procedure at a predetermined cycle.

  First, similarly to S20 to S24 in FIG. 8, determination of whether or not the execution conditions for detecting the fuel property are satisfied, acquisition of the dynamic viscosity, acquisition of the fuel density, calculation of C / H, average Calculation of the number of carbons is performed (S30 to S34).

  Then, based on the C / H of the fuel calculated in S33 and the average carbon number of the fuel calculated in S34 using the map of C / H and average carbon number stored in advance and the ignition delay time, The ignition delay time TA is calculated for the fuel currently being used, and the ignition delay change amount ΔT, which is the difference between the ignition delay time TA and the ignition delay time TB of the standard fuel determined in advance, It calculates as (S35).

  Subsequently, correction of the fuel injection timing by the injector 17 is performed based on the ignition delay change amount ΔT calculated in S35 (S36). At this time, if the ignition delay change amount ΔT is a positive value, the fuel injection timing is corrected to the advance side as the ΔT becomes larger. Further, if the ignition delay change amount ΔT is a negative value, the fuel injection timing is corrected to the retard side as the ΔT becomes larger on the negative side.

  In addition, if C / H and an average carbon number are decided, an average hydrogen number will be decided. Therefore, it is also possible to calculate the ignition delay time based on C / H and the average number of hydrogen.

  According to the third embodiment described above, the following effects can be obtained.

  If C / H and the average carbon number representing the easiness of fuel are used as fuel component data, the correlation between the C / H and the average carbon number and the ignition delay time in the combustion chamber 11b is used to obtain a standard fuel It is possible to grasp the change amount of the ignition delay time when using. Then, the injection timing is shifted to the advancing side or the retarding side based on the change amount of the ignition timing. As a result, even if the properties of the currently used fuel deviate from the standard fuel, the deviation can be corrected, and appropriate combustion control can be implemented.

(Other embodiments)
The above embodiment may be modified, for example, as follows.

  -The inventor is able to estimate the lower heating value of the fuel based on the dynamic viscosity and the density of the fuel, and the lower heating value of the fuel has a strong correlation with C / H (carbon hydrogen ratio) I focused on In this case, it is conceivable to calculate a lower calorific value correlated to C / H as fuel component data and to execute combustion control based on the lower calorific value.

The reason why the lower calorific value and C / H have a strong correlation is as follows. First, the lower calorific value HL [kJ] is expressed by the following equation (1).
HL = 3400 × c + 117500 (h−o / 8) + 10500 × s−2520 × w (1)
C is a carbon mass [kg], h is a hydrogen mass [kg], o is an oxygen mass [kg], s is a sulfur mass [kg], and w is a water mass [kg].

Here, since the amount of oxygen, the amount of sulfur, and the amount of water are small, if these are omitted, equation (1) can be simplified as equation (2).
HL = k1 × c + k2 × h (2)
In this case, since the hydrogen molecular weight is 1, it is possible to calculate c / h (carbon hydrogen ratio) from HL, and it can be said that the correlation between the lower calorific value and C / H is strong. According to the inventor of the present invention, it is confirmed that the lower calorific value and C / H have the relationship shown in FIG.

  When performing combustion control based on the low heating value, the ECU 40 uses the map or correlation function that defines the relationship between the dynamic viscosity and density of the fuel and the low heating value, and generates low temperature based on the dynamic viscosity and density of the fuel. Calculate the quantity. Then, based on the lower calorific value, the increase / decrease correction of the fuel injection amount is performed. At this time, the correction amount on the increase side of the fuel injection amount is increased as the lower heating value is smaller than the standard lower heating value, and the lower heating value is larger than the standard lower heating value. It is better to increase the correction amount on the weight reduction side. In addition, when correcting the fuel injection amount, the injection amount correction may be performed in consideration of the engine water temperature, the oil temperature, and the intake temperature in addition to the low heating value.

  The C / H (carbon hydrogen ratio) may be calculated based on the dynamic viscosity and the density of the fuel, and the combustion state of the engine may be feedback controlled based on the C / H. In the following configuration, C / H which is fuel component data is corrected by a combustion state parameter representing an actual combustion state in the engine 10, and combustion control is performed based on the corrected C / H. FIG. 11 is a functional block diagram showing an outline of the combustion state feedback control. The functions shown in FIG. 11 are implemented as arithmetic processing of the ECU 40.

  In FIG. 11, in the first calculation unit M1, C / H (hereinafter, referred to as first C / H) based on the fuel density detected by the fuel density sensor 32 and the dynamic viscosity detected by the dynamic viscosity sensor 33. Calculate The second calculation unit M2 calculates C / H (hereinafter, referred to as second C / H) based on an actual ignition delay time which is an actual ignition delay time in the engine 10. The actual ignition delay time is calculated based on the in-cylinder pressure detected by the in-cylinder pressure sensor 31. The actual ignition delay time is also a parameter used for ignition timing correction control.

  As a combustion state parameter of the engine 10, an engine rotation fluctuation amount may be used instead of or in addition to the actual ignition delay time. The engine rotation fluctuation amount may be calculated as a fluctuation amount of the engine rotation speed in comparison with the case where a standard fuel is used.

  The deviation calculation unit M3 calculates the deviation between the first C / H and the second C / H. The C / H correction unit M4 calculates the final C / H by correcting the first C / H calculated by the first calculation unit M1 with the deviation calculated by the deviation calculation unit M3. The C / H correction unit M4 corresponds to a correction unit. Then, using this final C / H, estimation of the amount of soot and smoke suppression control are performed.

  When C / H is calculated based on the dynamic viscosity and the density of the fuel, it is considered that the C / H may include an error component from the combustion state of the engine 10. In this respect, in the above configuration, C / H (first C / H) calculated based on the dynamic viscosity and density of the fuel is corrected by the actual ignition delay time which is the combustion state parameter of the engine 10, and C after the correction is made. Combustion control is performed based on / H (final C / H). Therefore, even if C / H includes an error component from the combustion state of the engine 10, the error component can be corrected, and more appropriate combustion control can be implemented.

  The calculation of the kinematic viscosity is not limited to one based on the detected value by the kinematic viscosity sensor 33. For example, the pressure of the fuel in the fuel passage from the common rail 20 to the injection hole of the injector 17 is detected by a pressure sensor, and a pressure waveform indicating time change of the detected fuel pressure is acquired. Then, the velocity of the pressure wave forming the acquired pressure waveform may be calculated, the density of the fuel may be calculated based on the velocity of the pressure wave, and the dynamic viscosity of the fuel may be calculated based on the density (more specifically, See open 2014-148906). Similarly, the pressure in the common rail 20 may be detected by a pressure sensor, and the detected pressure waveform in the common rail 20 may be analyzed to calculate the dynamic viscosity. The kinematic viscosity may be calculated using any known method.

  In the second embodiment, the predetermined combustion position in the combustion area may be a combustion center position which is the center of the combustion area, instead of the combustion tip position. The center of the combustion region is a position between the position closest to the tip of the injector 17 and the position of the combustion tip in the combustion region. In this case, in S26, the first distance is shorter than in the case of the combustion tip position, and in S28, the second distance is shorter than in the case of the combustion tip position.

  By calculating the combustion center position in the combustion region, it can be known whether the combustion region is biased to the vicinity of the wall surface of the combustion chamber 11 b or the vicinity of the tip of the injector 17. Furthermore, by using the combustion center position, it can be known whether or not the combustion region is biased in the vicinity of the wall surface of the combustion chamber 11b even when the fuel spray is in contact with the wall surface of the combustion chamber 11b.

  -It is also possible to combine at least any two of the smoke suppression control in the first embodiment, the combustion position control in the second embodiment, and the injection timing control in the third embodiment. For example, when the smoke suppression control and the combustion position control are performed in combination, when the combustion tip position is far from the first distance with high smoke fuel, processing other than the increase of the injection pressure is performed as smoke suppression control. As position control, it is preferable to increase the intake pressure without reducing the injection pressure. Also, when the combustion tip position is closer than the second distance with high smoke fuel, processing other than the increase in intake pressure is performed as smoke suppression control, and the injection pressure is not reduced as the combustion position control. It is good to carry out the increase.

  10: engine (diesel engine) 11b: combustion chamber 17: injector (fuel injection valve) 40: ECU (dynamic viscosity acquisition means, density acquisition means, component calculation means, control means).

Claims (1)

A control device (40) for controlling a diesel engine (10) including a fuel injection valve (17) for injecting fuel into a combustion chamber (11b),
Dynamic viscosity acquisition means for acquiring the dynamic viscosity of the fuel;
Density acquisition means for acquiring the density of the fuel;
The carbon number is calculated using the relationship in which the carbon number decreases as the kinematic viscosity decreases, based on the kinematic viscosity acquired by the kinematic viscosity acquisition unit, and the carbon number is calculated based on the density acquired by the density acquisition unit. Component calculation means for calculating the ratio of the amount of carbon to the amount of hydrogen contained in the fuel by the number of hydrogen and the number of hydrogen by using the relationship that the number of hydrogen increases as the density is smaller, and the number of carbon and the number of hydrogen
A high smoked fuel in which the amount of soot discharged when performing normal combustion control assuming a fuel of a standard property is larger than a predetermined amount based on the ratio calculated by the component calculation means A soot amount determining unit that determines whether or not
Control means for performing smoke suppression control for smoke suppression as combustion control regarding combustion of fuel injected from the fuel injection valve into the combustion chamber when it is determined that the fuel is high smoke fuel ;
A control device for a diesel engine, comprising: