JP2015190371A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of improving the combustion properties of an internal combustion engine by estimating a cetane number at low cost with high accuracy.SOLUTION: The present application concerns a control device of an internal combustion engine burning a fuel by compressive ignition, stores a cetane number map (120) regulating the relation between an exhaust temperature and a fuel cetane number in a storage unit (108) in advance, estimates a cetane number corresponding to a detected exhaust temperature on the basis of the cetane number map (120), and corrects a control parameter of the internal combustion engine on the basis of the estimated cetane number.

Description

  The present invention relates to a technical field of a control device for an internal combustion engine that performs compression ignition combustion of a fuel such as a diesel engine.

  Fuels such as light oil are used in compression combustion type internal combustion engines such as diesel engines, but the cetane number of commercially available fuels is not always constant (particularly in emerging countries). Therefore, when a fuel having a cetane number different from the assumed cetane number is used, there is a possibility that a reduction in fuel consumption performance and an increase in harmful substances in the exhaust gas may occur due to a decrease in combustion characteristics. Especially in the low load region of the internal combustion engine, the influence is large, and white smoke and misfire may occur. As one of solutions to such a problem, it is conceivable to estimate the cetane number of actual fuel used in the internal combustion engine and reflect the estimation result in the operation control of the internal combustion engine.

  Various methods have been proposed for estimating the cetane number of fuel. For example, Patent Document 1 discloses that a combustion state in an internal combustion engine is monitored by an in-cylinder pressure sensor and the result is compared with a standard combustion state to determine whether or not the cetane number is abnormal. .

JP 2007-77945 A

  In Patent Document 1, the detection value of the in-cylinder pressure sensor is used to estimate the cetane number. Such an in-cylinder pressure sensor is expensive and has a problem of increasing costs.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can improve the combustion characteristics of the internal combustion engine by estimating the cetane number with low cost and accuracy.

In order to solve the above problem, an internal combustion engine control apparatus according to an aspect of the present invention is an internal combustion engine control apparatus that compresses and ignites fuel, and includes an exhaust temperature detection unit that detects an exhaust temperature of the internal combustion engine; ,
A storage unit that stores a cetane number estimation map that predefines a relationship between the exhaust temperature and the cetane number of the fuel, and an estimated value of the cetane number corresponding to the detected exhaust temperature based on the cetane number estimation map A cetane number estimating unit for calculating the control parameter, a control parameter setting unit for setting a control parameter for the internal combustion engine corresponding to the operating state of the internal combustion engine, and correcting the control parameter based on the estimated value of the cetane number A control parameter correction unit and a control unit that controls the internal combustion engine based on the corrected control parameter are provided.

  The inventor of the present application has found that in an internal combustion engine that compresses and ignites fuel, the exhaust temperature depends on the cetane number of the fuel used in the internal combustion engine. In this aspect, the relationship between the exhaust temperature and the cetane number is stored in the storage unit in advance as a cetane number estimation map, and the cetane number corresponding to the actual measured value of the exhaust temperature is based on the cetane number estimation map. Is accurately estimated. Thus, in this aspect, it is not necessary to use an expensive sensing device (for example, an in-cylinder pressure sensor or an air flow meter), and combustion improvement of the internal combustion engine is possible at low cost.

  The storage unit further stores an exhaust temperature map preliminarily defining a relationship between an operating state of the internal combustion engine and an exhaust temperature corresponding to the operating state, and an operating state detection unit that detects the operating state of the internal combustion engine And obtaining an exhaust temperature corresponding to the detected operating state based on the exhaust temperature map, and obtaining a reference value of the cetane number corresponding to the obtained exhaust temperature based on the cetane number estimation map. The control parameter correction unit may further include a reference cetane number calculation unit, and the control parameter correction unit may correct the control parameter based on a difference between the estimated value of the cetane number and the reference value.

  According to this aspect, based on the exhaust temperature map, a standard exhaust temperature is obtained from the actual operating state of the internal combustion engine, and further, a cetane number reference value corresponding to the standard exhaust temperature is obtained. This makes it possible to compare the estimated value of the cetane number estimated based on the actual measured value of the exhaust temperature based on the reference value. And by performing correction according to the error between the cetane number of the fuel actually used in the internal combustion engine and the reference value, it is possible to effectively suppress the deterioration of the combustion characteristics due to the fluctuation of the cetane number It becomes.

  The cetane number estimation unit may calculate an estimated value of the cetane number when the operating state of the internal combustion engine is in a steady state.

According to this aspect, the cetane number is estimated when the internal combustion engine is in a steady state. Here, the steady state widely means that the operating state of the internal combustion engine is stable, and does not include a transient state. In the steady state, various parameters that affect the estimation accuracy of the cetane number (such as the operating state such as the rotational speed and the fuel injection amount, or the exhaust temperature) can be detected more accurately than in the transient state. Cetane number can be estimated.
For example, at the time of cold start of an internal combustion engine, when the temperature of cooling water or lubricating oil is equal to or higher than a warm-up determination temperature threshold, and then the temperature change amount is less than a predetermined value within a predetermined period ( It is determined that the warm-up is complete.

  The control parameter may be a fuel injection timing of the internal combustion engine, and the control parameter correction unit may correct the phase of the fuel injection timing as the estimated value of the cetane number decreases.

  When the cetane number of the fuel used for the internal combustion engine is lowered, the ignitability of the fuel in the cylinder is lowered. In this aspect, when a fuel having a low cetane number is used in this manner, the ignition is promoted by advancing the phase of the fuel injection timing, and the influence due to the decrease in the cetane number can be improved.

  In this case, the combustion injection timing includes a pilot fuel injection timing and a main fuel injection timing, and the control parameter correction unit advances the phase of the main fuel injection timing as the estimated value of the cetane number decreases. At the same time, the phase of the pilot fuel injection timing may be corrected so as to be retarded.

  When fuel injection into the cylinder consists of pilot fuel injection and main fuel injection, combustion is performed by advancing the phase of the main fuel injection timing to suppress the influence of the cetane number decrease, as described above. The characteristics can be improved. On the other hand, the inventors have clarified that it is important that the pilot fuel injection timing is appropriately spaced from the main fuel injection timing. As a result, the pilot fuel injection timing is retarded opposite to the main fuel injection timing, so that the interval between the main fuel injection timing and the pilot fuel injection timing can be appropriately adjusted to further improve the combustion characteristics. .

  The control parameter is an EGR amount for recirculating a part of the exhaust gas of the internal combustion engine to the intake system, and the control parameter correction unit reduces the EGR amount as the estimated value of the cetane number decreases. You may correct to.

  According to this aspect, when the ignitability of the fuel in the cylinder is lowered due to the lower cetane number of the fuel used in the internal combustion engine, the EGR amount is reduced. As a result, the oxygen concentration in the intake air of the internal combustion engine increases, and the reduced ignitability can be improved.

  The control parameter is a capacity of a variable supercharger provided in an exhaust system of the internal combustion engine, and the control parameter correction unit is configured to reduce the capacity of the variable supercharger as the estimated value of the cetane number decreases. You may correct | amend so that may become small.

  According to this aspect, when the ignitability of the fuel in the cylinder is lowered due to the low cetane number of the fuel used in the internal combustion engine, the capacity of the variable supercharger is reduced. Thereby, the intake flow rate (oxygen amount) of the internal combustion engine increases, and the reduced ignitability can be improved.

  The cetane number estimation map defines a relationship between the exhaust temperature and the cetane number for a plurality of operating states of the internal combustion engine, and the control parameter correction unit is configured to determine the cetane number in the plurality of operating states. The estimated value of the cetane number may be obtained by averaging the results of estimating the cetane number.

  According to this aspect, the estimated cetane number of the fuel used in the internal combustion engine is calculated by averaging the cetane numbers estimated in a plurality of operating states, so that the control accuracy can be further improved.

  The exhaust temperature map may be defined so as to include a relationship between the operation state before the completion of warming-up of the internal combustion engine and an exhaust temperature corresponding to the operation state.

  According to this aspect, the cetane number can be estimated early before the warm-up is completed by defining the exhaust temperature before the warm-up is completed in the exhaust temperature map. Therefore, it is possible to effectively suppress white smoke and misfire that are likely to occur particularly during cold start.

  The operating state includes an external environment parameter related to an external environment of the internal combustion engine, and the exhaust temperature map defines a relationship between the external environment parameter and an exhaust temperature corresponding to the external environment parameter. Also good.

  The combustion characteristics of an internal combustion engine are also affected by external environmental parameters of the internal combustion engine such as atmospheric temperature and atmospheric pressure. In this aspect, by preparing an exhaust temperature map corresponding to the external environment parameter, it is possible to estimate the cetane number in consideration of the influence of the external environment parameter.

  The operating state may include an intake state of the internal combustion engine, and the exhaust temperature map may define a relationship between the intake state and an exhaust temperature corresponding to the intake state.

  According to this aspect, by preparing an exhaust temperature map corresponding to the intake state (for example, the temperature of intake air flowing through the intake manifold, the pressure of intake air, etc.), estimation of the cetane number taking into account the effect of the intake state Is possible. In particular, the influence of the disturbance of the intake system (for example, clogging of the intake filter and deterioration of the heat exchange performance of the intercooler) can be taken into account in this aspect, so that it is possible to estimate the cetane number with higher accuracy.

  The control parameter setting unit sweeps the control parameter, and the cetane number estimation unit calculates the estimated value of the cetane number based on a change in the exhaust temperature detected by the exhaust temperature detection unit. Good.

  According to this aspect, the cetane number can be estimated from the change of the exhaust temperature accompanying the sweep change of the control parameter. For example, the control parameter is changed within a predetermined range (for example, a range of several percent) from a reference value set according to the operating state of the internal combustion engine, and a change in the exhaust temperature at that time is detected. At this time, the change in the exhaust temperature is typically obtained as a linear function of the control parameter. At this time, the inventor's research has revealed that the slope of the linear function depends on the cetane number used in the internal combustion engine. Therefore, the cetane number can be estimated by storing the relationship between the cetane number and the inclination in the storage unit in advance and collating with the inclination obtained based on the actual measurement value. Thus, in this aspect, since the cetane number estimation is performed based on the exhaust temperature in a plurality of control parameters, a highly accurate estimation result can be obtained.

  In this case, the internal combustion engine includes a DPF (Diesel Particulate Filter) that supplements particulate matter contained in the exhaust gas in the exhaust system, and the control parameter setting unit performs the regeneration process of the DPF, The control parameter may be swept.

  According to this aspect, when the exhaust system includes the DPF for removing the particulate matter contained in the exhaust gas, the control parameter is swept during the regeneration process for burning the particulate matter accumulated in the DPF. To do. When the DPF process is performed while the vehicle is running or during a predetermined work, if the control parameter is changed in a sweep manner, there is a possibility that the output to the engine load side will be affected. In this aspect, when the output to the load side is in the stopped state and the operator manually performs the DPF regeneration process, the influence on the load side can be avoided by performing the sweep change of the control parameter.

  The control parameter may be fuel injection timing.

  The exhaust temperature map may be corrected by actual measurement data that is a result of past measurement of the operating state of the internal combustion engine.

  For example, the exhaust gas temperature map is prepared in common for a plurality of internal combustion engines having the same specification, but in reality, each internal combustion engine has individual differences. In this aspect, actual measurement data (for example, a measurement result in factory inspection) that is a measurement result performed in the past for each individual internal combustion engine is stored in the storage unit, and the exhaust temperature map is the actual measurement data. Is corrected based on As a result, control taking into account the individual characteristics of the internal combustion engine becomes possible, and control accuracy can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can improve the combustion characteristic of an internal combustion engine can be provided by estimating a cetane number cheaply and accurately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. It is a conceptual diagram which shows the internal structure of ECU which concerns on Example 1 as a functional block. 4 is a flowchart illustrating a control method performed by the ECU according to the first embodiment for each process. It is a graph which shows an example of the time-sequential change of the rotation speed of an engine and fuel injection amount. It is a graph which shows an example of the time-sequential change of the cooling water temperature at the time of engine cold start. It is a graph which shows the operating point of the engine which concerns on Example 1 with a torque curve. It is an example of the map for cetane number estimation memorize | stored in the memory | storage part. It is an example of an exhaust temperature map. 3 is a graph showing fuel injection timing of the engine according to the first embodiment. It is a graph which shows the relationship between the main fuel injection timing in each cetane number, and the amount of unburned components contained in exhaust gas. It is a graph which shows the relationship between the amount of EGR in each cetane number, and the amount of unburned matter contained in exhaust gas. It is a graph which shows the relationship between the variable turbo capacity | capacitance in each cetane number, and the unburned matter discharge amount contained in exhaust gas. It is a flowchart which shows the control method implemented with respect to the engine which concerns on Example 2 for every process. It is a schematic diagram which shows the engine which concerns on Example 3 with a periphery structure. It is a figure which shows an example of the exhaust temperature map corresponding to the cooling water temperature of 80 degreeC in Example 3. FIG. It is a figure which shows an example of the exhaust temperature map corresponding to the cooling water temperature of 25 degreeC in Example 3. FIG. It is a schematic diagram which shows the engine which concerns on Example 4 with a periphery structure. It is a figure which shows an example of the exhaust temperature map corresponding to atmospheric pressure 101.3kPa in Example 4. FIG. It is a figure which shows an example of the exhaust temperature map corresponding to atmospheric pressure 90kPa in Example 4. FIG. It is a schematic diagram which shows the engine which concerns on Example 5 with a periphery structure. It is a figure which shows an example of the exhaust temperature map corresponding to the intake air temperature of 50 degC in Example 5. FIG. It is a figure which shows an example of the exhaust temperature map corresponding to the intake temperature of 30 degC in Example 5. FIG. 12 is a flowchart illustrating a control method performed by an ECU according to a sixth embodiment for each process. It is a conceptual diagram which shows the internal structure of ECU which concerns on Example 6 as a functional block. It is a graph which shows an example of a function map. It is a conceptual diagram which shows the internal structure of ECU which concerns on Example 7 as a functional block. It is a flowchart which shows notionally a mode that an exhaust-gas temperature map is correct | amended by the actual measurement data memorize | stored in the memory | storage part.

  Hereinafter, embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an example.

  In the present embodiment, a case in which a diesel engine (hereinafter referred to as “engine” as appropriate) 1 that is an internal combustion engine equipped with a common rail fuel injection device is handled as a control target will be described as an example. In particular, the engine 1 according to the present embodiment is mounted on an industrial vehicle such as a hydraulic excavator (not shown), and its output is used as a power source for traveling, as well as the transportation of heavy objects. It is also used as a power source for various operations.

(Example 1)
FIG. 1 is a schematic diagram illustrating an engine 1 according to a first embodiment together with peripheral components. The engine 1 is a 6-cylinder diesel engine. Exhaust gas discharged from each cylinder 2 joins in the exhaust manifold 4 and then drives an exhaust turbine 8 a provided in the exhaust pipe 6. The exhaust turbine 8 a is connected to a compressor 8 b provided in the intake pipe 10. The compressor 8 b constitutes an exhaust turbocharger 8 together with the exhaust turbine 8 a, and is driven coaxially with the drive of the exhaust turbine 8. As a result, the air taken in from the intake pipe 10 passes through the air filter 12, and is then compressed and raised in temperature by the compressor 8b. The compressed and pressurized air is cooled by an intercooler 14 disposed on the downstream side, and then supplied to each cylinder 2 via an intake manifold 16.
An intake throttle 18 for adjusting the amount of intake air supplied to each cylinder 2 is provided on the downstream side of the intercooler 14 in the intake pipe 10.

  An EGR (exhaust gas recirculation) pipe 20 branches from the exhaust pipe 6 upstream of the exhaust turbine 8 a and is connected to the intake pipe 10 on the downstream side of the intake throttle 18. Is now refluxing. The EGR pipe 20 is provided with an EGR cooler 22 to cool the high-temperature exhaust gas. The recirculation amount (EGR amount) of the EGR gas is adjusted by the EGR valve 24 provided in the EGR pipe 20.

The exhaust gas discharged from each cylinder 2 is supplied to the exhaust gas aftertreatment device 26 after driving an exhaust turbine 8a provided in the exhaust pipe 6 to become a power source of the compressor 8b. The exhaust gas after-treatment device 26 is integrally composed of an oxidation catalyst (DOC) 28 and a diesel particulate filter (DPF) 30. In the DOC 28, oxygen contained in the exhaust gas is used to oxidize unburned substances mainly composed of hydrocarbons (HC) in the exhaust gas and decompose them into water (H ₂ 0) and carbon dioxide (CO ₂ ). .

  The DPF 30 performs purification by collecting particulate matter (PM) in the exhaust gas. When the accumulated amount of PM collected by the DPF 30 is increased, the DPF is blocked and the engine output is reduced. Therefore, the regeneration process is performed in the DPF 30 at a predetermined timing. During the regeneration process of the DPF 30, the fuel in the exhaust gas is oxidized by the DOC 28 on the upstream side to raise the temperature of the exhaust gas, and the exhaust gas that has reached a high temperature is sent to the DPF 30 to burn the accumulated PM.

  Various operations of the engine 1 configured as described above are performed by the ECU 100 which is an electronic control unit. The ECU 100 realizes the operation of the engine 1 by acquiring a signal from each sensor that detects the operation state of the engine 1 and controlling a control parameter according to the operation state. In FIG. 1, an exhaust temperature sensor 32 that detects the temperature of the exhaust gas in the exhaust pipe 6 is representatively exemplified as sensors for detecting parameters relating to the operating state of the engine 1, and the detected value is sent to the ECU 100. It is configured to be ingestible.

  The operating state widely includes various parameters related to the operation of the engine 1. For example, the engine speed, load, fuel injection timing, fuel injection amount, cooling water temperature / pressure, lubricating oil temperature / pressure, etc. included. Of these operating states, typically, the engine speed, load, cooling water temperature / pressure, lubricating oil temperature / pressure, and the like are detected by sensors (not shown in FIG. 1). May include a rotation speed sensor, a load sensor, a cooling water temperature sensor / pressure sensor, a lubricating oil temperature sensor / pressure sensor, and the like. On the other hand, the fuel injection timing and the fuel injection amount can typically be grasped as a control signal of the ECU 100, but it goes without saying that these may be configured to be detectable by sensors.

  The ECU 100 controls the operation of the engine 1 by setting a control parameter according to the operating state of the engine 1 as a basic control (the setting of a control parameter by a control parameter setting unit described later corresponds to this). In the present embodiment, in addition to such basic control, as will be described below, control parameters are corrected based on the estimated value of the cetane number of the fuel used in the engine 1.

  FIG. 2 is a conceptual diagram illustrating the internal configuration of the ECU 100 according to the first embodiment as a functional block. FIG. 3 is a flowchart illustrating a control method performed by the ECU 100 according to the first embodiment for each process.

  As shown in FIG. 2, the ECU 100 sets an exhaust temperature detecting unit 102 that detects the exhaust temperature of the engine 1, an operating state detecting unit 104 that detects the operating state of the engine 1, and sets control parameters according to the operating state. Control parameter setting unit 106, storage unit 108 for storing cetane number estimation map 120 and exhaust temperature map 122, cetane number estimation unit 110 for calculating an estimated value of cetane number, and reference cetane for calculating a reference value of cetane number The fuel cell includes a valence calculation unit 111, a control parameter correction unit 112 that corrects a control parameter based on the estimated cetane number, and a control unit 114 that controls the engine 1 according to the corrected control parameter. It functions as a control device for an engine that performs compression ignition combustion.

The ECU 100 having such a configuration controls the engine 1 according to the flowchart shown in FIG.
First, the ECU 100 determines whether or not the control start condition is met (step S101). Here, the control start condition is a determination condition for starting the estimation calculation of the cetane number, for example, a condition that defines whether or not the engine 1 is in a steady state. The steady state broadly means that the operating state of the internal combustion engine is stable, and does not include a transient state. In the steady state, various parameters that affect the estimation accuracy of the cetane number (such as the operating state such as the rotational speed and the fuel injection amount, or the exhaust temperature) can be detected more accurately than in the transient state. Cetane number can be estimated.

  Here, FIG. 4 is a graph showing an example of a time-series change in the rotational speed of the engine 1 and the fuel injection amount. In FIG. 4, it is determined that the engine 1 is in a steady state when the amount of change in the rotation speed and the fuel injection amount in the predetermined period t0 is less than a preset threshold value (for example, ± 20 rpm).

FIG. 5 is a graph showing an example of a time series change in the coolant temperature when the engine 1 is cold started. In this case, when the temperature of the cooling water or the lubricating oil is equal to or higher than the warm-up determination temperature threshold and the temperature change amount is less than the predetermined value within a predetermined period, the steady state (warm-up completion state) is determined. Good.
FIG. 5 shows a state where the cooling water temperature rises with time and the warm-up is completed at time t1. In this case, the ECU 100 monitors the cooling water temperature, so that the actual measurement value is equal to or higher than a threshold value T0 defined in advance as a typical reference temperature at the time of completion of warm-up, and the amount of change in the predetermined period t0 is a predetermined threshold value. It is good to determine that it is a warm-up completion state by determining whether it is less than.
Such warm-up completion determination may be performed based on the lubricating oil temperature instead of the cooling water temperature.
Further, in this embodiment, after determining the completion of warm-up in this way, by executing each process described later, the exhaust temperature map 122 can be prepared for a temperature region that is equal to or higher than the warm-up completion temperature in all operating states. It is sufficient (in other words, since it is certain that the temperature is not lower than the warm-up completion temperature after step S102, it is not necessary to prepare the exhaust temperature map 122 corresponding to the temperature lower than the warm-up completion temperature). Therefore, the capacity of the storage unit 108 that stores the exhaust temperature map 122 can be efficiently reduced.

  When the establishment of the control start condition is confirmed in this way (step S101: YES), the exhaust temperature detection unit 102 acquires the exhaust temperature from the exhaust temperature sensor 32 provided in the exhaust pipe 6 (step S102). The cetane number estimation unit 110 reads the cetane number estimation map 120 by accessing the storage unit 108 and calculates an estimated value of the cetane number corresponding to the exhaust temperature acquired from the exhaust temperature detection unit 102 (step S103). ).

  FIG. 6 is a graph showing the operating point of the engine 1 according to the first embodiment together with the torque curve, and FIG. 7 is an example of the cetane number estimation map 120 stored in the storage unit 8.

  As shown in FIG. 6, the operating point of the engine 1 is the operating point L.I. 1 to the operation point A-D where the work can be performed. At the operating point A, the output torque is variable according to work while maintaining the rotational speed at Ne (A), and at the operating point B, the output torque is variable according to work while maintaining the rotational speed at Ne (B). Yes, at the operating point C, the output torque is variable according to work while maintaining the rotational speed at Ne (C), and at the operating point D, the output torque is variable according to work while maintaining the rotational speed at Ne (D). It is variable. Such a transition to the driving point A-D is implemented by selecting with a dial that can be operated by the driver of the work vehicle on which the engine 1 is mounted, for example.

  As shown in FIG. 7, in the cetane number estimation map 120, the relationship between the cetane number of the fuel and the exhaust temperature is defined in advance for each of these operating points, and the exhaust temperature increases as the rotational speed at the operating point increases. A tendency to increase is shown. Moreover, the exhaust temperature tends to decrease as the cetane number of the fuel increases.

  In step S103, the cetane number estimation unit 110 refers to such a cetane number estimation map 120 to calculate an estimated value of the cetane number corresponding to the exhaust gas temperature, which is an actual measurement value. Subsequently, the reference cetane number calculation unit 111 reads the exhaust temperature map 122 by accessing the storage unit 108 and acquires the operation state from the operation state detection unit 102, so that the operation state is based on the exhaust temperature map 122. Is calculated (step S104).

Here, FIG. 8 is an example of the exhaust temperature map 122, and standard exhaust temperatures with respect to the engine speed and the fuel injection amount in a specific operation state are defined. The reference cetane number calculation unit 111 calculates the exhaust temperature corresponding to the operating state of the engine 1 by referring to such an exhaust temperature map 122. For example, when the operation state (the rotation speed is 1500 rpm and the fuel injection amount is 30 mm ³ / inj) is acquired by the operation state detection unit 102, the exhaust temperature 340 ° C. corresponding to the operation state is obtained based on the exhaust temperature map 122. Is required.

  Subsequently, the reference cetane number calculation unit 111 reads the cetane number estimation map 120 by accessing the storage unit 108, and based on the cetane number estimation map 120, the cetane number corresponding to the exhaust temperature calculated in step S104. Is calculated (step S105).

  Here, the control parameter correction unit 112 obtains a difference between the estimated value of the cetane number calculated in step S103 and the reference value of the cetane number calculated in step S105, and whether or not the difference is larger than a preset threshold value. Is determined (step S106). As a result, when the difference is larger than the threshold value (step S106: YES), the control parameter setting unit 106 corrects the control parameter set according to the operating state of the engine 1 based on the difference (step S107).

  Here, control parameter correction control in step S107 will be described taking fuel injection timing as an example. FIG. 9 is a graph showing the fuel injection timing of the engine 1 according to the first embodiment. The broken line shows the fuel injection timing before correction, and the solid line shows the fuel injection timing after correction.

  The control parameter correction unit 112 corrects the phase of the main fuel injection timing to advance as shown in FIG. 9 as the estimated value of cetane number calculated in step S103 decreases. Generally, when the cetane number of the fuel used in the engine 1 is lowered, the ignitability of the fuel in the cylinder is lowered. When the fuel having a low cetane number is used in this way, the phase of the fuel injection timing By advancing, it is possible to promote ignition and to improve the influence of a decrease in cetane number.

  Here, FIG. 10 is a graph showing the relationship between the main fuel injection timing and the amount of unburned fuel (HC) contained in the exhaust gas at each cetane number. According to this, in each cetane number, it is shown that the amount of unburned fuel (HC) emission decreases as the main fuel injection timing is advanced. This indicates that the combustion characteristics in the cylinder are improved. The control parameter correction unit 112 may correct the main fuel injection timing so that it falls below a preset allowable unburned fuel (HC) discharge amount as shown in FIG.

  Further, as shown in FIG. 9, the combustion injection timing of the engine 1 is further subjected to pilot injection for improving the ignitability before the main fuel injection. The control parameter correction unit 112 corrects the pilot fuel injection timing in addition to the correction of the main fuel injection timing. According to the research by the present inventor, it has been found that it is important that the interval between the pilot fuel injection timing and the main fuel injection timing is appropriate. Accordingly, the control parameter correction unit 112 appropriately adjusts the interval between the main fuel injection timing and the pilot fuel injection timing by delaying the pilot fuel injection timing opposite to the main fuel injection timing. Improve combustion characteristics.

  In step S107, an EGR amount for recirculating a part of the exhaust gas of the engine 1 to the intake system may be corrected as a control parameter. FIG. 11 is a graph showing the relationship between the EGR amount at each cetane number and the unburned component (HC) emission amount contained in the exhaust gas. In this case, the control parameter correction unit 112 increases the oxygen concentration in the intake air of the engine 1 to improve the reduced ignitability by correcting the EGR amount so that the estimated cetane number decreases. be able to.

  If the exhaust turbocharger 8 is a variable supercharger, the capacity of the exhaust turbocharger 8 may be corrected as a control parameter in step S107. Here, FIG. 12 is a graph showing the relationship between the variable turbo capacity at each cetane number and the amount of unburned component (HC) contained in the exhaust gas. In this case, the control parameter correction unit 112 increases the intake air flow rate (oxygen amount) of the engine 1 by correcting the capacity of the exhaust turbocharger 8 to be smaller as the estimated value of the cetane number becomes lower, Reduced ignitability can be improved.

  When the correction parameter is corrected based on the estimated cetane number in this way, the control unit 114 outputs a control signal based on the corrected control parameter and controls the engine 1 (step S108).

  When the difference is equal to or smaller than the threshold value in step S106 (step S106: NO), the control parameter correction unit 112 advances the process to step S108 without correcting the control parameter.

As described above, according to the first embodiment, the cetane number corresponding to the actually measured value of the exhaust temperature can be accurately estimated based on the cetane number estimation map 120. Thus, in this embodiment, it is not necessary to use an expensive sensing device (for example, an in-cylinder pressure sensor or an air flow meter), and combustion improvement of the internal combustion engine is possible at low cost.
In particular, based on the exhaust temperature map 122, a standard exhaust temperature is obtained from the actual operating state of the engine 1, and further, a cetane number reference value corresponding to the standard exhaust temperature is obtained. This makes it possible to compare the estimated value of the cetane number estimated based on the actual measured value of the exhaust temperature based on the reference value. And by performing correction according to the error between the cetane number of the fuel actually used in the engine 1 and the reference value, it is possible to effectively suppress the deterioration of the combustion characteristics due to the change of the cetane number. It becomes.

  It should be noted that such improvement of combustion characteristics using cetane number estimation is particularly effective in the low load region of the engine 1 where white smoke and misfire are likely to occur. For example, the above control may be performed only when the load of the engine 1 is detected by a sensor and the load is less than a predetermined threshold.

(Example 2)
FIG. 13 is a flowchart illustrating, for each process, a control method performed on the engine 1 according to the second embodiment.
In the following description, unless otherwise specified, the configuration is the same as that of the first embodiment, and repeated descriptions are omitted as appropriate.

  When engine 1 in a stopped state is started, ECU 100 detects an idle state of engine 1 (step S201), and determines whether or not a control start condition is satisfied in the idle state (step S202). This control start condition is the same as that in step S101 described above. That is, it is determined whether the engine 1 in the idle state has been warmed up and has reached a steady state.

  When the control start condition is satisfied (step S202: YES), the ECU 100 calculates an estimated value of the cetane number according to the same procedure as steps S102 to S104 (step S203).

  Subsequently, the ECU 100 determines whether or not the engine 1 has shifted from the idle state to another operating state (step S204). Here, the other operation state means an operation point other than the idle state such as operation points A to D as shown in FIG. When there is such a transition of the operation state (step S204: YES), the ECU 100 determines whether or not the control start condition is satisfied again in the operation state after the transition (step S205). That is, for example, when moving to the operating point A, it is determined again whether or not a steady state is established at the operating point A.

  When the control start condition is satisfied again (step S205: YES), the ECU 100 calculates an estimated value of the cetane number based on the exhaust temperature according to the same procedure as steps S102 to S104 (step S206).

  When the cetane number is estimated in a plurality of operating states in this way, the control parameter correction unit 112 averages the plurality of cetane numbers calculated in steps S203 and S206, thereby obtaining a final estimated value of cetane number. Is obtained (step S207). The control parameter correction unit 112 corrects the control parameter according to the same procedure as steps S106 to S107 (step S208), and controls the engine 1 based on the corrected control parameter (step S209).

  As described above, according to the second embodiment, the estimated cetane number used in the engine 1 is calculated by averaging the cetane numbers estimated in a plurality of operating states, so that the control accuracy can be further improved. .

(Example 3)
FIG. 14 is a schematic diagram illustrating the engine 1 according to the third embodiment together with the peripheral configuration, and FIG. 15 is a diagram illustrating an example of the exhaust temperature map 122 defined for each cooling water temperature in the third embodiment. FIG. 15A shows a case where the cooling water temperature is typically 80 ° C., and FIG. 15B shows a case where the cooling water temperature is 25 ° C.

As shown in FIG. 14, the engine 1 according to the present embodiment includes a cooling water temperature sensor 34 that detects the cooling water temperature, and as shown in FIG. 15, an exhaust temperature map 122 indicates the engine speed and the fuel injection amount. In addition, it is different from the above embodiment in that it is prepared for each operation state including the coolant temperature of the engine 1.
In the following description, overlapping description of other common configurations will be omitted as appropriate.

  In the present embodiment, the operation state detection unit 104 acquires the coolant temperature detected by the coolant temperature sensor 34 as one of the operation states of the engine 1. Then, the reference cetane number calculating unit 111 searches the exhaust temperature map 122 corresponding to the acquired cooling water temperature from the plurality of exhaust temperature maps 122 stored in the storage unit 108, and based on the searched exhaust temperature map 122. To calculate the standard cetane number. Thus, in this embodiment, the cetane number can be estimated with higher accuracy by adding the coolant temperature to the operating state of the engine 1.

In particular, as shown in FIG. 15B, the exhaust temperature map 122 is defined so as to include the relationship between the operating state before the completion of warming up of the engine 1 and the exhaust temperature corresponding to the operating state. In this way, by defining the exhaust temperature before the warm-up is completed in the exhaust temperature map 122, the cetane number can be estimated at an early stage before the warm-up is completed. Therefore, it is possible to effectively suppress white smoke and misfire that are likely to occur particularly during cold start.
In this embodiment, it goes without saying that the lubricating oil temperature may be used instead of the cooling water temperature.

Example 4
FIG. 16 is a schematic diagram showing the engine 1 according to the fourth embodiment together with the peripheral configuration, and FIG. 17 is a diagram showing an example of the exhaust temperature map 122 defined for each atmospheric pressure in the fourth embodiment. FIG. 17A shows a case where the atmospheric pressure is typically 101.3 kPa, and FIG. 17B shows a case where the atmospheric pressure is 90 kPa.

As shown in FIG. 16, the engine 1 according to this embodiment includes an atmospheric pressure sensor 34 that detects atmospheric pressure, which is a kind of external environment parameter, and, as shown in FIG. 17, an exhaust temperature map 122 has an engine speed. In addition to the fuel injection amount and the fuel injection amount, it is different from the above embodiment in that it is prepared for each operation state including the atmospheric pressure of the engine 1.
In the following description, overlapping description of other common configurations will be omitted as appropriate.

  In the present embodiment, the operation state detection unit 104 acquires the coolant temperature detected by the atmospheric pressure sensor 36 as one of the operation states of the engine 1. Then, the reference cetane number calculation unit 111 searches the exhaust temperature map 122 corresponding to the acquired atmospheric pressure from the plurality of exhaust temperature maps 122 stored in the storage unit 108, and based on the searched exhaust temperature map 122 Calculate the standard cetane number. Thus, in this embodiment, the cetane number can be estimated with higher accuracy by adding the atmospheric pressure to the operating state of the engine 1.

As described above, in this embodiment, the atmospheric pressure, which is an external environment parameter, is included in the operating state, and the exhaust temperature corresponding to the atmospheric pressure is defined by the exhaust temperature map 122. The combustion characteristics of the engine 1 are also affected by external environmental parameters such as atmospheric pressure. However, by preparing the exhaust temperature map 122 so as to correspond to the external environmental parameters as in this embodiment, the external environmental parameters are prepared. It is possible to estimate the cetane number with high accuracy, taking into account the effects of.
In this embodiment, the atmospheric pressure is adopted as the external environment parameter, but it goes without saying that the atmospheric temperature may be used instead.

(Example 5)
FIG. 18 is a schematic diagram illustrating the engine 1 according to the fifth embodiment together with the peripheral configuration, and FIG. 19 is a diagram illustrating an example of the exhaust temperature map 122 defined for each intake air temperature in the fifth embodiment. FIG. 19A shows a case where the intake air temperature is typically 50 degC, and FIG. 19B shows a case where the intake air temperature is 30 degC.

As shown in FIG. 18, the engine 1 according to this embodiment includes an intake air temperature sensor 38 that detects the intake air temperature in the intake manifold 16, and as shown in FIG. 19, an exhaust gas temperature map 122 shows the engine speed and fuel injection. In addition to the quantity, it is different from the above embodiment in that it is prepared for each operation state including the intake air temperature.
In the following description, overlapping description of other common configurations will be omitted as appropriate.

In the present embodiment, the operation state detection unit 104 acquires the coolant temperature detected by the intake air temperature sensor 38 as one of the operation states of the engine 1. Then, the reference cetane number calculating unit 111 searches the exhaust temperature map 122 corresponding to the acquired intake air temperature from the plurality of exhaust gas temperature maps 122 stored in the storage unit 108, and based on the searched exhaust gas temperature map 122. Calculate the standard cetane number. Thus, in the present embodiment, the cetane number can be estimated with higher accuracy by taking the intake air temperature into consideration in the operating state of the engine 1. In particular, since the influence of disturbance of the intake system (for example, clogging of the air filter 12 or deterioration of the heat exchange performance of the intercooler 14) can be taken into account, it is possible to estimate the cetane number with higher accuracy.
Needless to say, the intake pressure may be adopted instead of the intake air temperature, which is a kind of intake state.

(Example 6)
In this embodiment, the exhaust gas temperature is changed by sweeping the control parameter set by the control parameter setting unit 106 based on the operating state of the engine 1, and the cetane number is estimated based on the behavior. Different from the embodiment.
In the following description, overlapping description of other common configurations will be omitted as appropriate.

FIG. 20 is a flowchart illustrating, for each process, a control method implemented by the ECU 100 according to the sixth embodiment.
First, the ECU 100 determines whether or not a control start condition is satisfied for the engine 1 (step S301). In this step, in addition to the steady state as in step S101, for example, the operation state of the engine 1 is affected by the sweep change of the control parameter as described later, so that the user of the engine 1 feels uncomfortable. It may be determined that the state is not given.

  Particularly in the present embodiment, in step S301, it is determined that the condition is satisfied when the regeneration process of the DPF 30 provided in the exhaust system of the engine 1 is performed. When the DPF process is performed while the vehicle is running or during a predetermined work, if the control parameter is changed in a sweep manner, there is a possibility that the output to the engine load side will be affected. In this embodiment, the output to the load side is in a stopped state, and when the operator manually performs the DPF regeneration process, the influence on the load side is avoided by changing the sweep of the control parameter. A sense of incongruity can be prevented.

Subsequently, when the control start condition is satisfied (step S301: YES), the control parameter setting unit measures the exhaust temperature by acquiring the detection value from the exhaust temperature sensor 32 while sweeping the control parameter (step S301: YES). Step S302).
In the present embodiment, the case where the fuel injection timing is adopted as the control parameter for changing the sweep will be described, but it goes without saying that other control parameters may be adopted.

  Step S302 will be specifically described. First, the cetane number estimation unit 110 acquires a detection value from the exhaust temperature sensor 32 at a specific fuel injection timing (typically, a control parameter value corresponding to the operating state of the engine 1). The detected exhaust temperature is stored in association with the fuel injection timing. Thereafter, the fuel injection timing is changed by sweeping, and a detected value is acquired again from the exhaust temperature sensor 32 at a different fuel injection timing, and the detected exhaust temperature is stored in association with the fuel injection timing. By repeating the sweep change of the fuel injection timing and the measurement of the exhaust gas temperature, the cetane number estimating unit 110 grasps the relationship between the exhaust gas temperature and the fuel injection timing as a function (typically, the exhaust gas temperature is 21 is expressed as a linear function with the fuel injection timing shown in FIG. 21 as a variable).

  FIG. 21 is a conceptual diagram showing the internal configuration of the ECU 100 according to the sixth embodiment as a functional block. The function map 124 predefines the relationship between the fuel injection timing and the exhaust gas temperature in each cetane number. Is different from the above embodiment in that it is stored.

  FIG. 22 is a graph showing an example of the function map 124, which shows the relationship between the fuel injection timing and the exhaust gas temperature for each cetane number. In the function map 124, the exhaust temperature at each cetane number is represented as a linear function with the fuel injection timing as a variable, and has a slope corresponding to the cetane number (that is, each linear function corresponds to the cetane number). Have a slope).

  The cetane number estimation unit 110 obtains an inclination from a function based on the actual measurement value obtained by sweeping the fuel injection timing as described above (step S303), and collates with the function map 124 shown in FIG. In step S304, the cetane number corresponding to the function having the inclination closest to the inclination is specified (step S305).

  When the cetane number is estimated in this way, the correction parameter control unit 111 corrects the correction parameter based on the estimated cetane number (step S306) as in step S107, and then the control unit 114 The engine 1 is controlled based on the corrected control parameter (step S307).

  As described above, according to the present embodiment, the cetane number can be estimated from the change in the exhaust temperature accompanying the sweep change of the control parameter. In particular, by sweeping the control parameter in this way, the exhaust gas temperature is substantially measured at a plurality of control parameters and the cetane number is estimated based on them, so that an accurate estimation result can be obtained.

  In particular, as shown in FIG. 22, even in the engine 1 using the fuel having the same cetane number, the measurement results vary among individuals. This means that the function map 124 includes information on individual differences of the engine 1. Therefore, in this embodiment, it is possible to carry out control based on accurate cetane number estimation that takes into account the influence of individual differences of the engine 1.

(Example 7)
FIG. 23 is a conceptual diagram showing the internal configuration of the ECU 100 according to the seventh embodiment as a functional block. FIG. 24 conceptually shows how the exhaust temperature map 122 is corrected by the actual measurement data 126 stored in the storage unit 108. It is a flowchart shown in FIG.

  The present embodiment is different from the above-described embodiment in that measured data 126 that is a result of past measurement of the operating state of the engine 1 is stored in the storage unit 108. The actual measurement data 126 is a result measured for each individual engine 1, for example, operating conditions (test fuel cetane number, engine speed, fuel injection amount) actually measured by a trial operation at the time of factory shipment of the individual engine 1. , Atmospheric pressure, air temperature, cooling water temperature, lubricating oil temperature, etc.) and measurement results (exhaust temperature).

  On the other hand, the exhaust temperature map 122 stored in the storage unit 108 is prepared, for example, for defining a standard relationship between the operating state and the exhaust temperature for each model number of the engine 1 having a common specification. When the ECU 100 uses the exhaust gas temperature map 122 for control, the ECU 100 corrects the standard exhaust gas temperature map 122 based on actually measured data prepared for each individual in this way. Thereby, the control which considered the individual characteristic of the engine 1 is attained, and control accuracy can be improved more.

  As described above, according to the above embodiment, the combustion characteristics of the engine 1 can be improved by estimating the cetane number with low cost and high accuracy.

  The present invention is applicable to a control device for an internal combustion engine that compresses and ignites and burns fuel, such as a diesel engine.

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 4 Exhaust manifold 6 Exhaust pipe 8 Exhaust turbocharger 8a Exhaust turbine 8b Compressor 10 Intake pipe 12 Air filter 14 Intercooler 16 Intake manifold 18 Intake throttle 20 EGR pipe 22 EGR cooler 24 EGR valve 26 Exhaust gas after-treatment device 28 Oxidation catalyst (DOC)
30 Diesel particulate filter (DPF)
32 Exhaust temperature sensor 34 Cooling water temperature sensor 36 Atmospheric pressure sensor 38 Intake air temperature sensor 100 ECU
102 Exhaust temperature detection unit 104 Operating state detection unit 106 Control parameter setting unit 108 Storage unit 110 Cetane number estimation unit 111 Reference cetane number calculation unit 112 Control parameter correction unit 114 Control unit 120 Cetane number estimation map 122 Exhaust temperature map 124 Function map 126 Measured data

Claims (15)

A control device for an internal combustion engine that performs compression ignition combustion of fuel,
An exhaust temperature detector for detecting the exhaust temperature of the internal combustion engine;
A storage unit for storing a cetane number estimation map preliminarily defining a relationship between the exhaust temperature and the cetane number of the fuel;
A cetane number estimation unit that calculates an estimated value of the cetane number corresponding to the detected exhaust temperature based on the cetane number estimation map;
A control parameter setting unit for setting a control parameter of the internal combustion engine in response to an operating state of the internal combustion engine;
A control parameter correction unit for correcting the control parameter based on the estimated value of the cetane number;
And a control unit that controls the internal combustion engine based on the corrected control parameter. The storage unit further stores an exhaust temperature map that preliminarily defines a relationship between the operating state of the internal combustion engine and the exhaust temperature corresponding to the operating state,
An operating state detector for detecting an operating state of the internal combustion engine;
A reference cetane for obtaining an exhaust temperature corresponding to the detected operating state based on the exhaust temperature map, and obtaining a reference value for the cetane number corresponding to the obtained exhaust temperature based on the cetane number estimation map A price calculation unit,
The control device for an internal combustion engine according to claim 1, wherein the control parameter correction unit corrects the control parameter based on a difference between the estimated value of the cetane number and the reference value.   3. The control device for an internal combustion engine according to claim 1, wherein the cetane number estimation unit calculates the estimated value of the cetane number when the operating state of the internal combustion engine is in a steady state. The control parameter is a fuel injection timing of the internal combustion engine,
The internal combustion engine according to any one of claims 1 to 3, wherein the control parameter correction unit corrects the phase of the fuel injection timing to advance as the estimated value of the cetane number decreases. Engine control device. The combustion injection timing includes a pilot fuel injection timing and a main fuel injection timing,
The control parameter correction unit corrects the phase so that the phase of the main fuel injection timing is advanced and the phase of the pilot fuel injection timing is retarded as the estimated value of cetane number decreases. Item 5. The control device for an internal combustion engine according to Item 4. The control parameter is an EGR amount for recirculating a part of the exhaust gas of the internal combustion engine to the intake system,
6. The control device for an internal combustion engine according to claim 1, wherein the control parameter correction unit corrects the EGR amount so as to decrease as the estimated value of the cetane number decreases. . The control parameter is a capacity of a variable supercharger provided in an exhaust system of the internal combustion engine,
The said control parameter correction | amendment part correct | amends so that the capacity | capacitance of the said variable supercharger may become small as the estimated value of the said cetane number becomes low, It is characterized by the above-mentioned. Control device for internal combustion engine. The cetane number estimation map defines a relationship between the exhaust temperature and the cetane number for a plurality of operating states of the internal combustion engine,
3. The control of the internal combustion engine according to claim 2, wherein the control parameter correction unit obtains the estimated value of the cetane number by averaging the results of estimating the cetane number in the plurality of operating states. apparatus.   3. The internal combustion engine according to claim 2, wherein the exhaust gas temperature map is defined so as to include a relationship between the operation state before the completion of warm-up of the internal combustion engine and an exhaust gas temperature corresponding to the operation state. Engine control device. The operating state includes an external environment parameter related to the external environment of the internal combustion engine,
The control apparatus for an internal combustion engine according to claim 2, wherein the exhaust temperature map defines a relationship between the external environment parameter and an exhaust temperature corresponding to the external environment parameter. The operating state includes an intake state of the internal combustion engine,
3. The control apparatus for an internal combustion engine according to claim 2, wherein the exhaust temperature map defines a relationship between the intake state and an exhaust temperature corresponding to the intake state. The control parameter setting unit sweeps and changes the control parameter,
The control device for an internal combustion engine according to claim 1, wherein the cetane number estimation unit calculates the estimated value of the cetane number based on a change in the exhaust temperature detected by the exhaust temperature detection unit. The internal combustion engine includes a DPF that supplements particulate matter contained in exhaust gas in an exhaust system,
The control apparatus for an internal combustion engine according to claim 12, wherein the control parameter setting unit sweeps and changes the control parameter during the regeneration process of the DPF.   14. The control device for an internal combustion engine according to claim 12, wherein the control parameter is a fuel injection timing.   The control apparatus for an internal combustion engine according to claim 2, wherein the exhaust gas temperature map is corrected by actual measurement data that is a result of past measurement of the operating state of the internal combustion engine.

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