JP5691910B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control apparatus that performs fuel injection control in accordance with an estimation result of engine fuel properties.

  2. Description of the Related Art Conventionally, there has been known a technique for estimating various properties related to the combustion performance of fuel used in an engine while the engine is running and adjusting various operating parameters of the engine. That is, an index corresponding to the content and concentration of the constituent components such as cetane number and octane number of the fuel is estimated, and the fuel injection amount, fuel injection timing, etc. are controlled according to these. Fuel combustion characteristics greatly affect combustion stability, engine output, exhaust performance, and the like. Therefore, accurately grasping the fuel properties is important in securing the soundness of the engine, the power performance of the vehicle, the environmental adaptability, and the like.

  As a fuel property estimation method, a method using input information from various sensors for detecting a combustion state of an engine has been proposed. For example, Patent Document 1 describes an engine control device that determines a fuel property based on an engine speed and a fuel injection amount in an idle operation state. In this technology, the correspondence between the engine speed and the fuel injection amount and the fuel property is mapped in advance, so that the fuel property can be grasped at a low cost without providing special sensors. It is said that the mixing ratio of different types of fuel such as high-octane gasoline can be estimated.

  Japanese Patent Application Laid-Open No. 2004-228561 detects the actual ignition timing of the fuel based on the amount of change in the cylinder pressure of the engine and determines the cetane number of the fuel based on the delay of the actual ignition timing from the reference ignition timing. An apparatus is described. In this technique, it is said that the cetane number can be accurately calculated by setting the fuel injection amount of the cylinder to be detected of the actual ignition timing during idle operation to a fixed predetermined value.

JP 2007-309210 A JP 2007-270816 A

  However, the input information such as the engine speed, the fuel injection amount, and the actual ignition timing as described in Patent Documents 1 and 2 above is not necessarily information that changes under the influence of specific fuel properties. It cannot be said that the desired fuel properties are accurately reflected.

  For example, the combustion performance of the fuel varies depending not only on the content of the constituent components but also on the fuel viscosity and the fuel temperature. This means that even when fuels having the same component content are used, the engine speed, the fuel injection amount, the actual ignition timing, and the like can change when the fuel viscosity and the fuel temperature are different. That is, when there are a plurality of types of fuel properties to be grasped, it is difficult to extract and observe only the influence of each fuel property on one input information. Therefore, there is a problem that it is difficult to improve the estimation accuracy of individual fuel properties based on each input information.

  In particular, the fuel properties of fuels used in compression ignition engines such as diesel engines and semi-diesel engines vary greatly in the amount of fuel injection due to the influence of not only the cetane number of the fuel but also the fuel viscosity. Therefore, for example, in the method described in Patent Document 2, it is difficult to separate the ignition delay time caused by the difference in cetane number from the ignition delay time caused by the difference in fuel viscosity. And the estimation accuracy of both the fuel viscosity is lowered.

One of the objects of the present case has been created in view of the above-described problems, and is to improve the estimation accuracy of the fuel property estimated when the compression ignition engine is operated.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) The engine control device disclosed herein includes at least a first estimation unit that estimates a cetane number of fuel based on a delay in the ignition timing of the engine, and at least based on the cetane number estimated by the first estimation unit. First correcting means for correcting the fuel injection timing. Further, based on the fuel injection amount for setting the rotation speed at the time of idling operation of the engine to a predetermined value, based on the fuel viscosity estimated by the second estimating means, the second estimating means for estimating the fuel viscosity, And at least second correction means for correcting the fuel injection amount. Further, after the correction by the first correction unit or the second correction unit is performed based on the result of the estimation by one of the first estimation unit and the second estimation unit, the fuel injection for performing the estimation by the other Control means are provided.

  The fuel injection control means separates the estimation by the first estimation means and the estimation by the second estimation means. That is, the fuel injection control means has a function of managing so that two types of estimation control are not performed simultaneously. In other words, the function of the fuel injection control means is a function that does not perform the estimation of the other until the correction based on at least one of the estimation results is completed.

(2) Moreover, it is preferable that the fuel injection control unit alternately performs the correction by the first correction unit and the correction by the second correction unit.
In this case, the estimation by the first estimation unit and the estimation by the second estimation unit are alternately performed. Specifically, the correction by the first correction unit is performed after the estimation by the first estimation unit, and the correction by the second correction unit is performed after the estimation by the second estimation unit. Is made. In such a cycle, estimation and correction are repeatedly performed.

(3) Further, the first correction means limits the correction value of the fuel injection timing to a predetermined upper limit value or less, and the second correction means limits the correction amount of the fuel injection amount to a predetermined upper limit value or less. It is preferable.
(4) In addition, a leak amount is provided that includes temperature detection means for detecting the temperature of the fuel, and wherein the second estimation means estimates the leak amount of the fuel injection amount based on the temperature detected by the temperature detection means. It is preferable that the fuel viscosity is estimated in consideration of the leakage amount estimated by the leakage amount estimation unit , as well as having an estimation unit.

(5) In addition, temperature detection means for detecting the temperature of the fuel is provided, and the second estimation means estimates the reliability of the estimated value of the fuel viscosity based on the temperature detected by the temperature detection means. Preferably, the second correction unit corrects at least the fuel injection amount based on the reliability of the estimated value of the fuel viscosity estimated by the viscosity correction value estimation unit .
(6) It is preferable that a crank angular speed detecting means for detecting a crank angular speed of the engine is provided. In this case, the first estimation unit estimates an ignition time based on the crank angular velocity, and an ignition delay period estimation that estimates an ignition delay period from the time when the fuel injection is completed to the ignition time. And cetane number estimating means for estimating the cetane number to be smaller as the ignition delay period is longer.

  (7) It is preferable that an idle control means is provided for adjusting the fuel injection amount correction amount so as to control the engine speed during idle operation to a predetermined value. In this case, it is preferable that the second estimation unit estimates the fuel viscosity higher as the correction amount adjusted by the idle control unit is larger.

  According to the disclosed engine control apparatus, the estimation based on the estimation result of one is corrected by separating each influence of the cetane number and the fuel viscosity on the engine operating state and performing each estimation. Therefore, the estimation accuracy of each fuel property can be improved. In addition, since correction targets based on the two estimation results are different, mutual collisions in control can be avoided, and the operating state of the engine can be converged to a desired state.

It is a figure showing the whole engine control device composition concerning one embodiment. It is a graph for demonstrating estimation calculation by this control apparatus, (a) is a graph which shows the relationship between a fuel cetane number and ignition time, (b) is a graph which shows the relationship between a fuel cetane number and an ignition delay period. is there. It is a graph for demonstrating the estimation calculation in this control apparatus, (a) is a graph which shows the relationship between the amount of leaks from a fuel system, and fuel temperature, (b) is the relationship between the sensitivity of fuel viscosity, and fuel temperature. (C) is a graph which shows the relationship between a fuel viscosity and the correction coefficient of the fuel injection quantity at the time of idle driving | operation. It is a flowchart which illustrates the procedure of the estimation calculation in this control apparatus. It is a flowchart which illustrates the procedure of the estimation calculation in the engine control apparatus which concerns on a modification, (a) concerns on determination of a fuel cetane number, (b) concerns on determination of fuel viscosity.

  The engine control apparatus will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. In addition, each configuration of the following embodiment can be selected as necessary, or may be appropriately combined, and various modifications can be made without departing from the spirit of the embodiment.

[1. Device configuration]
The engine control device 1 of the present embodiment is applied to a multi-cylinder diesel engine 10 (compression ignition engine) mounted on a vehicle. FIG. 1 shows one of a plurality of cylinders 11 (cylinders) provided in the engine 10. A piston 12 that reciprocates in the cylinder 11 is connected to a crankshaft 13 via a connecting rod.

  An injector 14 for fuel injection is provided on the upper portion of the cylinder 11. The tip of the injector 14 is provided so as to protrude into the cylinder 11, and the fuel is directly injected into each cylinder 11. A delivery pipe 15 is connected to the base end side of the injector 14, and fuel pressurized by a feed pump (not shown) is supplied to each injector 14.

  The fuel injection amount from the injector 14 and the injection timing thereof are controlled by the engine control device 1 described later. For example, a control pulse signal is transmitted from the engine control device 1 to each injector 14 and the injection port of each injector 14 is opened only during a period corresponding to the magnitude (drive pulse width) of the control pulse signal. Thus, the fuel injection amount becomes an amount corresponding to the magnitude of the control pulse signal, and the injection timing corresponds to the time when the control pulse signal is transmitted.

  In the vicinity of the crankshaft 13, a crank angle sensor 16 (crank angular velocity detecting means) for detecting the rotational speed of the crankshaft 13 is provided. For example, a disc-shaped crank plate having irregularities formed on the outer edge is fixed to the crankshaft 13. On the other hand, the crank angle sensor 16 is fixed in the vicinity of the outer edge portion of the crank plate, detects the uneven shape of the crank plate, and outputs a crank pulse signal. The crank pulse signal output here is transmitted to the engine control device 1.

  The cycle of the crank pulse signal becomes shorter as the crankshaft 13 rotates faster, and the time density of the crank pulse signal corresponds to the actual engine speed Ne (engine speed) and the angular speed ω of the crankshaft 13. . Therefore, it can be said that the crank angle sensor 16 is a means for detecting the engine speed Ne and the angular velocity ω.

  In the middle of the delivery pipe 15, a fuel temperature sensor 17 (temperature detection means) that detects the temperature T (fuel temperature) of the fuel supplied to each injector 14 is provided. Information on the detected fuel temperature T is transmitted to the engine control device 1. The fuel temperature T affects the viscosity of the fuel. The higher the temperature, the lower the fuel viscosity.

  This vehicle is provided with an engine control device 1 (Engine Electronic Control Unit) as an electronic control device. The engine control device 1 is configured as, for example, an LSI device or a built-in electronic device in which a microprocessor, ROM, RAM, etc. are integrated, and other electronic control devices, a crank angle sensor 16 and a fuel temperature sensor 17 via a communication line or an in-vehicle network. Connected to various sensors.

  The engine control device 1 is an electronic control device that controls a wide range of systems related to the engine 10 such as an ignition system, a fuel system, an intake / exhaust system, and a valve operating system. Specific control objects of the engine control device 1 include the fuel injection amount and injection timing from the injector 14, the valve lift and valve timings of the intake and exhaust valves, the intake amount (throttle valve opening), and the EGR amount ( EGR valve opening). In the present embodiment, the function of the engine control device 1 will be described focusing on so-called idle speed control that is performed during idling of the engine 10 and control related to estimation of fuel properties that is performed during idle speed control.

[2. Control configuration]
As shown in FIG. 1, the engine control apparatus 1 includes a first estimation unit 2, a first correction unit 3, a second estimation unit 4, a second correction unit 5, a fuel injection control unit 6, and an idle control unit 7. It is done. Each of these functions may be realized by an electronic circuit (hardware), may be programmed as software, or some of these functions may be provided as hardware, and the other part may be software. It may be a thing.

  The idle control unit 7 (idle control means) performs idle speed control, and controls the fuel injection amount when the engine 10 is idling. The idle speed control is a control for stably maintaining the engine speed Ne at a predetermined idle speed in the absence of an accelerator request.

  Here, the fuel injection amount necessary to stabilize the engine speed Ne is calculated as needed, and a control pulse signal corresponding to this is output to the injector 14. Further, the fuel injection amount during idle speed control is defined as a value obtained by multiplying the basic injection amount by the correction coefficient k. Of course, the correction coefficient k may have a positive or negative value, and the fuel injection amount at the time of idle speed control may be defined as “basic injection amount × (1 + k)”. The method will be described. For example, a correction coefficient k having a magnitude corresponding to the value of the engine speed Ne is set, and the fuel injection amount injected from each injector 14 is feedback controlled.

  When the engine speed Ne decreases below the idle speed, the idle control unit 7 automatically sets a feedback correction coefficient k having a magnitude corresponding to the decrease amount, and multiplies the basic injection amount by the correction coefficient k. A control pulse signal is output to the injector 14 so that an amount of fuel corresponding to the determined value is injected. On the other hand, when the engine speed Ne rises higher than the idle speed, the feedback correction coefficient k is automatically set small according to the amount of increase. The value of the correction coefficient k set here corresponds to the fuel injection amount actually injected from the injector 14 and is also transmitted to the second estimation unit 4.

  The first estimation unit 2, the first correction unit 3, the second estimation unit 4, the second correction unit 5, and the fuel injection control unit 6 perform fuel property estimation control and correction control corresponding thereto. . Here, two types of fuel properties, cetane number and viscosity, are estimated, and the operating parameters of the engine 10 are corrected according to the respective fuel properties.

  The 1st estimation part 2 (1st estimation means) implements estimation control regarding the cetane number of fuel. Here, an estimated value of the cetane number is calculated based on a delay in the ignition timing of the engine 10. The cetane number estimation calculation is performed when a predetermined condition regarding the operating state of the engine 10 is established. Hereinafter, this predetermined condition is referred to as a cetane number estimation condition.

  Specific conditions for estimating the cetane number are arbitrary, but it is preferable to estimate when the combustion state in the cylinder 11 is relatively stable. In the present embodiment, the cetane number estimation condition is that the engine 10 is in an idle operation state, and that the viscosity estimation calculation and the correction control related thereto by the second estimation unit 4 and the second correction unit 5 are not being performed. .

The first estimation unit 2 is provided with an ignition timing estimation unit 2a, an ignition delay period estimation unit 2b, and a cetane number estimation unit 2c as means for performing a cetane number estimation calculation.
The ignition timing estimation unit 2a (ignition timing estimation means) estimates the ignition time of the fuel in the cylinder 11 based on the angular velocity ω of the crankshaft 13. Here, the time at which the angular velocity ω becomes equal to or higher than a predetermined value is estimated as the ignition time. In this embodiment, the time when the time density of the crank pulse signal transmitted from the crank angle sensor 16 becomes equal to or higher than a predetermined density is estimated as the ignition time. The ignition time estimated here is transmitted to the ignition delay period estimation unit 2b.

  The ignition delay period estimation unit 2b (ignition delay period estimation means) estimates the elapsed time from the time when the fuel injection in each cylinder 11 is completed to the ignition time as the “ignition delay period”. When it can be considered that the end time of fuel injection when the engine 10 is in an idling operation state is almost constant, the ignition time (standard ignition time) when using a standard cetane number is used as a reference. The elapsed time until the ignition time calculated by the ignition timing estimation unit 2a may be referred to as an “ignition delay period”. The ignition delay period estimated here is transmitted to the cetane number estimation unit 2c.

  The cetane number estimation unit 2c (cetane number estimation means) estimates the cetane number of the fuel based on the ignition time estimated by the ignition timing estimation unit 2a or the ignition delay period estimated by the ignition delay period estimation unit 2b. To do. Here, for example, the cetane number is estimated using the relationship shown in FIGS. 2 (a) and 2 (b).

  When a fuel having a low cetane number is used, the ignition time is delayed, that is, the ignition delay period is extended as compared with the case where a fuel having a high cetane number is used. Therefore, assuming that the time at which fuel injection is completed is constant, it is estimated that the cetane number is lower as the ignition time is later, or the cetane number is lower as the ignition delay period is longer. Information on the cetane number of the fuel estimated here is transmitted to the first correction unit 3.

  The first correction unit 3 (first correction means) performs correction control based on the cetane number of the fuel. Here, at least the fuel injection timing is corrected based on the cetane number estimated by the first estimation unit 2. In the present embodiment, in addition to the fuel injection timing, the fuel injection amount, the intake air amount, the EGR amount (exhaust gas recirculation amount) and the like are also corrected.

  For example, as the cetane number is lower, control for moving the fuel injection timing to the advance side is performed, and the ignition time is brought closer to the standard ignition time. Further, the lower the cetane number of the fuel, the more the premixing of the fuel is promoted with the extension of the ignition delay period, and the combustion reaction becomes steep, so that the noise (combustion noise) at the time of combustion increases. Therefore, control is performed to decrease the intake air amount as the cetane number is lower, or control to decrease the combustion speed by increasing the EGR amount to optimize the combustion speed. These intake air amount and EGR amount may be obtained by interpolating correction values using a preset map.

  However, if the correction values for the fuel injection timing, the fuel injection amount, the intake air amount, and the EGR amount are too large, the operating state of the engine 10 may change suddenly. Therefore, the first correction unit 3 sets upper limit values for these correction values. Provided to limit correction accompanied by a change greater than a predetermined upper limit value.

  As the cetane number of the fuel is lower, the ignition time tends to be later than the top dead center passage time of the piston, so that the isovolume is lowered and the output torque of the engine 10 is reduced. On the other hand, if the ignition time is optimized by correcting the fuel injection timing, the output torque of the engine 10 increases. Further, the output torque is changed by correcting the fuel injection amount. Therefore, the control based on the cetane number affects the operating state of the engine 10 which is a premise of the control based on the viscosity of the fuel described below.

  The 2nd estimation part 4 (2nd estimation means) performs the estimation control regarding the viscosity of a fuel. Here, the viscosity is estimated based on the fuel injection amount necessary to maintain the engine speed Ne at a predetermined idle speed during the idle speed control. Similar to the cetane number estimation calculation, the viscosity estimation calculation is also performed when a predetermined condition regarding the operating state of the engine 10 is satisfied. Hereinafter, such a predetermined condition is referred to as a viscosity estimation condition.

  Although specific viscosity estimation conditions are arbitrary, it is preferable to estimate when the combustion state in the cylinder 11 is relatively stable. In the present embodiment, the viscosity estimation condition is that the engine 10 is in an idle operation state, and that the cetane number estimation calculation and the correction control related thereto by the first estimation unit 2 and the first correction unit 3 are not being performed. .

The second estimation unit 4 includes a leak amount estimation unit 4a, a viscosity correction value estimation unit 4b, and a viscosity estimation unit 4c as means for performing viscosity estimation control.
The leak amount estimation unit 4 a (leak amount estimation means) estimates the fuel leak amount based on the fuel temperature T detected by the fuel temperature sensor 17. Here, for example, the amount of leak is estimated using the relationship shown in FIG. The leak amount is the amount of fuel leaked from a seal part of a fuel system, a solenoid valve or the like.

  As the fuel temperature T is higher, the amount of leakage increases, and the value of the correction coefficient k in the idling operation state of the engine 10 slightly increases. That is, even if the fuel viscosity is the same, if the leak amount increases, the fuel injection amount during idle speed control will increase. Therefore, in the present embodiment, the influence of the leak amount is considered in order to accurately estimate the viscosity. Information on the leak amount estimated here is transmitted to the viscosity estimation unit 4c.

  The viscosity correction value estimator 4b (viscosity correction value estimation means) estimates the viscosity estimation sensitivity based on the fuel temperature T. Here, for example, the sensitivity is estimated using the relationship shown in FIG. The sensitivity here means the magnitude of the influence of the fuel viscosity on the fuel injection amount (in other words, the reliability of the fuel viscosity estimated from the fuel injection amount).

  As the fuel temperature T is lower, the viscosity is more easily reflected in the fuel injection amount, that is, the estimated viscosity value is estimated to be accurate. On the other hand, the higher the fuel temperature T, the lower the reliability of the estimated viscosity value. Therefore, in this embodiment, the controllability is improved by reflecting this sensitivity in the control related to the fuel viscosity. Information on the sensitivity estimated here is transmitted to the second correction unit 5.

  The viscosity estimator 4c estimates the viscosity of the fuel based on the correction coefficient k transmitted from the idle controller 7 or by adding a leak amount to the correction coefficient k. Here, for example, the viscosity is estimated using the relationship shown in FIG.

  When a fuel with a low viscosity is used, the frictional resistance and the viscosity resistance increase compared to when a fuel with a high viscosity is used, so the amount of fuel actually injected from the injector 14 decreases. In other words, assuming that the cetane number of the fuel is constant, the amount of fuel required to maintain the engine speed Ne at a constant idle speed changes depending on the viscosity, and the lower the viscosity, the correction factor k (fuel injection amount) increases. Therefore, it is estimated that the larger the correction coefficient k (the larger the fuel injection amount), the higher the fuel viscosity.

  In addition, when performing the estimation considering the leak amount estimated by the leak amount estimation unit 4a, for example, the leak amount is converted into a correction coefficient, the units are aligned, and the viscosity is calculated based on the value obtained by subtracting this from the correction coefficient k. May be estimated. Information on the viscosity estimated here is transmitted to the second correction unit 5.

  The second correction unit 5 (second correction means) performs correction control based on the fuel viscosity. Here, at least the fuel injection amount is corrected based on the viscosity and sensitivity estimated by the second estimation unit 4. For example, the fuel injection amount is increased as the viscosity is lower, and the actual fuel amount provided for the combustion reaction in the cylinder 11 is optimized.

  If the sensitivity is less than the predetermined sensitivity, it is determined that the reliability of the estimated viscosity is low, and the correction amount of the fuel injection amount is decreased. Alternatively, the correction may be temporarily stopped when the sensitivity is lower than the predetermined sensitivity, and the correction may be restarted when the sensitivity is equal to or higher than the predetermined sensitivity (for example, when the fuel temperature T is decreased). Note that, similarly to the first correction unit 3, the second correction unit 5 sets the upper limit value for the correction value of the fuel injection amount, and performs control for limiting the rapid increase / decrease in fuel.

  The output torque of the engine 10 changes due to the correction of the fuel injection amount by the second correction unit 5. For example, when the fuel injection amount is increased and the fuel concentration in the cylinder 11 is increased, the ignitability of the fuel is improved. Therefore, the control based on the viscosity of the fuel affects the operating state of the engine 10 which is the premise of the control based on the cetane number.

  The fuel injection control unit 6 (fuel injection control means) manages the execution states of the two controls so that the control related to the cetane number and the control related to the fuel viscosity are not performed simultaneously. Here, the time from when the estimation calculation is performed by the first estimation unit 2 to when the correction by the first correction unit 3 is performed, and after the estimation calculation by the second estimation unit 4 is performed, the second correction unit Each estimation calculation and correction control are separated so that the time until the correction according to 5 is performed does not overlap.

  As described above, the correction control (control based on the cetane number) in the first correction unit 3 affects the estimation calculation in the second estimation unit 4, and the correction control in the second correction unit 5 (based on the viscosity of the fuel). Control) affects the estimation calculation in the first estimation unit 2. Therefore, if these correction controls and estimation calculations are performed simultaneously in parallel, the other control may be performed before the result of one control is reflected in the operating state of the engine 10. Mutual interference can occur. In this case, the results of the two estimation calculations vibrate, and the operating state of the engine 10 may not converge to a certain state.

  Therefore, in the present embodiment, the fuel injection control unit 6 arbitrates between these two types of correction control and estimation calculation, and manages so that the other control is not performed while one control is being performed. Here, the cetane number estimation condition and the viscosity estimation condition are determined, and a control signal for permitting or prohibiting the estimation calculation is output to each of the first estimation unit 2 and the second estimation unit 4 according to the determination result. The fuel injection control unit 6 alternately performs these two types of correction control and estimation calculation. That is, after one estimation calculation and correction control are reflected in the operating state of the engine 10, the other estimation calculation is performed.

[3. flowchart]
FIG. 4 is a flowchart illustrating a control procedure performed by the engine control apparatus 1. A series of control shown in this flowchart is repeatedly performed inside the engine control apparatus 1. On the flowchart, a control flow relating to cetane number and a control flow relating to fuel viscosity are provided in series. The former corresponds to steps A10 to A50, and the latter corresponds to steps A60 to A100. That is, the control flow related to the cetane number and the control flow related to the fuel viscosity are separated from each other. Thereby, each implementation state of two types of estimation control is divided | segmented.

  In step A10, the fuel injection control unit 6 determines whether or not the cetane number estimation condition is satisfied. For example, if the combustion state is in an idling operation state, the process proceeds to step A20 assuming that the cetane number estimation condition is satisfied. On the other hand, if the cetane number estimation condition is not satisfied, the process proceeds to step A60, and the viscosity estimation condition is determined.

  In step A20, the crank pulse signal transmitted from the crank angle sensor 16 is read into the engine control device 1. In the subsequent step A30, the ignition timing estimation unit 2a estimates the time when the time density of the crank pulse signal is equal to or higher than a predetermined density as the ignition time. This time density corresponds to the angular speed ω of the crankshaft 13, and the time when the density becomes equal to or higher than the predetermined density corresponds to the ignition time. Further, the ignition delay period estimation unit 2b estimates the elapsed time from the time when the fuel injection is completed to the ignition time as the ignition delay period.

  In Step A40, the cetane number estimation unit 2c estimates the cetane number based on the ignition time and the ignition delay period. Note that the cetane number may be estimated based on one of the ignition time and the ignition delay period, or the average value of two cetane numbers based on both may be used as the final estimated value.

  In Step A50, the first correction unit 3 performs correction control based on the cetane number estimated in the previous step. Here, for example, as the cetane number is lower, the fuel injection timing is corrected to the advance side, the intake air amount is corrected to decrease, and the EGR amount is corrected to increase. At this time, the fuel injection amount may also be corrected. Since an upper limit is set for the correction value of the fuel injection timing, the correction value of the intake air amount, the correction value of the EGR amount, and the correction value of the fuel injection amount, a sudden change in the operating state of the engine 10 is prevented. Control corresponding to the estimated cetane number is reflected in the operating state of the engine 10 at this step.

  In subsequent Step A60, the fuel injection control unit 6 determines whether or not the viscosity estimation condition is satisfied. For example, when the engine 10 is in the idle operation state, the control flow relating to the fuel viscosity is started following the control flow relating to the cetane number, and the process proceeds to Step A70. On the other hand, when the viscosity estimation condition is not satisfied, this flow is finished as it is.

  In step A <b> 70, information on the fuel temperature T detected by the fuel temperature sensor 17 and information on the correction coefficient k transmitted from the idle control unit 7 are read into the second correction unit 5. The correction coefficient k read here reflects the operation state of the engine 10 corrected in step A50. In subsequent step A80, the leak amount estimation unit 4a estimates the fuel leak amount based on the fuel temperature T. Further, the viscosity correction value estimation unit 4b estimates the viscosity estimation sensitivity based on the fuel temperature T.

  In step A90, the viscosity of the fuel is estimated by the viscosity estimation unit 4c based on the correction coefficient k and the leak amount. The viscosity may be estimated based only on the correction coefficient k, or may be estimated in consideration of the leak amount. In Step A100, the second correction unit 5 performs correction control based on the viscosity and sensitivity estimated in the previous step.

Here, for example, the fuel injection amount is corrected to increase as the viscosity decreases. Since an upper limit is also set for the correction value of the fuel injection amount, sudden changes in operating conditions, torque shocks, and the like are prevented. Further, when the sensitivity is less than the predetermined sensitivity, the correction amount of the fuel injection amount may be decreased.
In the process of repeatedly performing such control, both the cetane number and the viscosity of the fuel are updated, and each value gradually converges to a true value.

[4. Action, effect]
In the engine control apparatus 1 described above, the fuel injection control unit 6 separates the execution states of the two types of estimation control, and the correction control related to the fuel cetane number and the correction control related to the viscosity are managed so as not to overlap in time. The That is, the other estimation is not performed until the correction based on one estimation result is at least completed.

  In this way, by separating the influence of the cetane number and the fuel viscosity on the operating state of the engine 10 and performing each estimation, the correction based on one estimation result is the premise for the other estimation. Can be reflected. For example, once the cetane number is estimated, the fuel injection timing is corrected based on the estimation, and the output torque of the engine 10 is changed. Thus, when the engine speed Ne changes, the fuel injection amount is also changed by the idle control unit 7. Since the viscosity of the fuel is estimated based on the fuel injection amount after the change, the estimated value of the viscosity is corrected, and the estimation accuracy of the viscosity can be improved.

Similarly, when the fuel injection amount is changed based on the viscosity estimation result, the ignition time changes accordingly. Since the cetane number is estimated again based on the ignition time after this change, the estimation accuracy of the cetane number can be improved.
Furthermore, since the correction targets based on the two estimation results are different, mutual collisions in control can be avoided. For example, the control content based on one estimation result and the control content based on the other estimation result cancel each other. There is no such thing. Therefore, the convergence of each estimation result is improved, and the operating state of the engine 10 can be converged to a desired state.

  Further, in the engine control apparatus 1 described above, since two types of correction control and estimation calculation are alternately performed, one estimation result can be continuously reflected in the other estimation content. That is, the convergence of each estimation result can be improved, and both the estimation accuracy of the cetane number and the estimation accuracy of the viscosity can be improved.

  The cetane number of the fuel is a parameter that can affect not only the ignition delay period but also the fuel injection amount (engine torque) during idle speed control. The viscosity of the fuel is determined by changing the engine speed to the idle speed. This is a parameter that can affect not only the amount of fuel injection necessary to maintain, but also the ignition delay period and combustion speed.

  On the other hand, in this embodiment, the relationship between the individual fuel properties and the influence of the fuel properties on the operating state of the engine 10 is deliberately fixed, and estimation calculation and correction control of the individual fuel properties are performed alternately. By doing so, the convergence of the estimation calculation is improved. Therefore, even if the estimation accuracy in one estimation operation is low, the estimation accuracy can be remarkably improved by repeatedly performing the estimation operation.

  In the engine control apparatus 1 described above, an upper limit is set for each correction value in the first correction unit 3 and the second correction unit 5. Thereby, the sudden change of the driving | running state of the engine 10 and generation | occurrence | production of a torque shock can be prevented. Furthermore, by reducing the amount of change in the state due to the correction, control hunting can be prevented, and the convergence of the estimation result of the fuel property can be further improved.

  In the engine control apparatus 1 described above, the leak amount estimation unit 4a estimates the fuel leak amount according to the fuel temperature T, and the viscosity estimation unit 4c estimates the viscosity in consideration of the influence of the leak amount. By such an estimation calculation, the amount of fuel actually injected from the injector 14 can be accurately grasped, the viscosity estimation accuracy can be improved, and the cetane number estimation accuracy can also be improved. be able to.

  In the engine control apparatus 1 described above, the viscosity correction value estimation unit 4b estimates the viscosity estimation sensitivity, and the second correction unit 5 corrects the fuel injection amount based on the sensitivity. Thus, the fuel injection amount can be corrected more accurately by judging the magnitude of the influence of the viscosity on the fuel injection amount with reference to the fuel temperature T, and the estimation results of each of the cetane number and the viscosity. Can be further improved.

  Regarding the control related to the cetane number, the engine control apparatus 1 estimates the fuel ignition time based on the angular velocity ω of the crankshaft 13. Thereby, it is possible to accurately grasp a sudden change in the rotation speed immediately after ignition, and to improve the estimation accuracy of the ignition time. Therefore, the ignition delay period can be accurately estimated, and the estimation accuracy of the cetane number can be improved.

  Further, regarding the control related to the viscosity, in the engine control apparatus 1 described above, the fuel viscosity is estimated based on the correction coefficient k of the fuel injection amount during idle operation in which the combustion state of the engine 10 is stable. The properties can be accurately grasped.

[5. Modified example]
In the above-described embodiment, the control flow related to the cetane number and the control flow related to the fuel viscosity are illustrated in series. However, each control flow can be expressed separately. For example, as shown in FIGS. 5A and 5B, it is conceivable that a cetane number estimation flow and a viscosity estimation flow are separately provided, and the execution timing is coordinated using a flag F.

  The flag F indicates that each control flow has been executed, and is set to F = 0 when the control flow related to the cetane number is completed, and is set to F = 1 when the control flow related to the viscosity is completed. Is done. It is assumed that the value (initial value) of the flag F when the engine control device 1 is turned on is F = 0. Also, among the steps in FIGS. 5A and 5B, the same reference numerals are given to the steps corresponding to the steps in FIG.

  As shown in FIG. 5A, in step A5 of the cetane number estimation flow, the fuel injection control unit 6 determines whether or not the flag F is F = 0. Here, when F = 0, the process proceeds to step A10, and when F ≠ 0 (that is, when F = 1), this flow is finished as it is. In step A55, which is performed after the correction control based on the cetane number is performed in step A50, the flag F is set to F = 1 in the fuel injection control unit 6.

  Further, as shown in FIG. 5B, in step A56 of the viscosity estimation flow, the fuel injection control unit 6 determines whether or not the flag F is F = 1. Here, when F = 1, the process proceeds to step A60, and when F ≠ 1 (that is, when F = 0), this flow is finished as it is. In step A105, which proceeds after the correction control based on the viscosity is performed in step A100, the fuel injection control unit 6 sets the flag F to F = 0.

  That is, the control flow related to the cetane number is started only when the flag F is F = 0, and the control flow related to the viscosity is started only when the flag F is F = 1. The flag F becomes F = 0 only when the control flow relating to the fuel viscosity is completed except when the engine control device 1 is turned on. The flag F becomes F = 0 because the cetane number is related. These two control flows are not executed at the same time because they are limited to when the control flow is completed.

  As described above, the fuel injection control unit 6 manages the two types of estimation control with the flag F, and after the correction based on one estimation result is performed, the other estimation is performed, and thus the same as in the above-described embodiment. It is possible to implement control that achieves the above effects.

  In the above-described embodiment, the control flow in which the estimation of the cetane number is performed prior to the estimation of the viscosity as illustrated in FIG. 4 is exemplified, but the order in which these are performed is arbitrary. Even if any estimation control is performed first, it is considered that the convergence value of the cetane number and the viscosity obtained by repeatedly performing the estimation control does not change.

  In the above-described embodiment, an example in which the time from when the correction based on one estimation control is performed until the other estimation control is not controlled is illustrated, but the correction is reflected in the operating state of the engine 10. In consideration of a time lag until the other, the start of the other estimation control may be delayed. In this case, for example, it is conceivable to add that “the elapsed time from the end of the control regarding the cetane number is a predetermined time or more” as one of the viscosity estimation conditions. Similarly, “one elapsed time from the end of control related to viscosity being a predetermined time or more” may be added as one of the cetane number estimation conditions.

By adding the start condition of each control as described above, one of the estimation results can be reliably reflected in the operating state of the engine 10, and the accuracy of estimating the fuel property can be further improved.
In the above-described embodiment, the engine 10 is in the idle operation state as one of the cetane number estimation condition and the viscosity estimation condition. However, specific conditions are not limited to this. For example, the fuel property may be estimated when the combustion state in the cylinder 11 can be considered stable even in a state other than the idle operation state.

DESCRIPTION OF SYMBOLS 1 Engine control apparatus 2 1st estimation part (1st estimation means)
2a Ignition timing estimation unit (Ignition timing estimation means)
2b Ignition delay period estimation unit (ignition delay period estimation means)
2c Cetane number estimation unit (cetane number estimation means)
3 First correction unit (first correction means)
4 Second estimation unit (second estimation means)
4a Leakage amount estimation unit (leakage amount estimation means)
4b Viscosity correction value estimation unit (viscosity correction value estimation means)
4c Viscosity estimation section 5 Second correction section (second correction means)
6 Fuel injection control unit (fuel injection control means)
7 Idle control unit (idle control means)
10 Engine 14 Injector 16 Crank angle sensor (Crank angular velocity detection means)
17 Fuel temperature sensor (temperature detection means)

Claims (7)

A first estimating means for estimating the cetane number of the fuel based on a delay in the ignition timing of the engine;
First correction means for correcting at least the fuel injection timing based on the cetane number estimated by the first estimation means;
Second estimating means for estimating a fuel viscosity based on a fuel injection amount for setting the number of revolutions during idling of the engine to a predetermined value;
Second correction means for correcting at least the fuel injection amount based on the fuel viscosity estimated by the second estimation means;
Fuel injection control means for performing estimation by the other after performing correction by the first correction means or the second correction means based on a result of estimation by one of the first estimation means and the second estimation means And an engine control device. The engine control apparatus according to claim 1, wherein the fuel injection control means alternately performs the correction by the first correction means and the correction by the second correction means. The first correction means limits the correction value of the fuel injection timing to a predetermined upper limit value or less;
The engine control apparatus according to claim 1 or 2, wherein the second correction means limits the correction amount of the fuel injection amount to a predetermined upper limit amount or less. Temperature detecting means for detecting the temperature of the fuel,
Wherein the second estimation means, based on the temperature detected by said temperature detecting means, and has a leakage quantity estimation means for estimating the amount of leakage of the fuel injection amount, the leakage amount estimated by the leakage amount estimating means The engine control device according to any one of claims 1 to 3 , wherein the fuel viscosity is estimated in consideration of Temperature detecting means for detecting the temperature of the fuel,
The second estimating means has a viscosity correction value estimating means for estimating reliability of the estimated value of the fuel viscosity based on the temperature detected by the temperature detecting means ,
Wherein the second correction means, based on the reliability of the estimated value of the fuel viscosity estimated by the viscosity correction value estimation means, and wherein the <br/> to correct at least the fuel injection amount, according to claim 1 The engine control device according to any one of to 4. A crank angular speed detecting means for detecting the crank angular speed of the engine;
The first estimating means is
Ignition timing estimating means for estimating an ignition time based on the crank angular velocity;
An ignition delay period estimation means for estimating an ignition delay period from the time when the fuel injection is completed to the ignition time;
6. The engine control device according to claim 1, further comprising a cetane number estimating unit configured to estimate the cetane number to be smaller as the ignition delay period is longer. Idle control means for adjusting the fuel injection amount correction amount so as to control the rotational speed during idle operation of the engine to a predetermined value;
The engine control apparatus according to claim 1, wherein the second estimation unit estimates the fuel viscosity to be higher as the correction amount adjusted by the idle control unit increases. .

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