JP4290715B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for a compression ignition internal combustion engine that burns by compressing an air-fuel mixture in a combustion chamber.

  Patent Document 1 discloses a control apparatus for a compression ignition internal combustion engine that performs premixed combustion. According to this apparatus, the actual ignition timing of the fuel is detected during the premixed combustion, and the ignition timing error that is a difference from the preset standard fuel ignition timing and the variation in the ignition timing error are detected. The property of the fuel is determined.

JP-A-2005-171818

  The engine operation region in which the premixed combustion is performed is, for example, a region indicated by hatching in FIG. 10 and is relatively narrow when viewed from the whole engine operation region. For this reason, the execution timing of the fuel property determination is delayed, the fuel injection timing is not suitable for the fuel property, and a misfire may occur.

  The present invention has been made paying attention to this point, and provides a control device for an internal combustion engine that can quickly and accurately determine the fuel properties, specifically, the cetane number of the fuel in use. Objective.

In order to achieve the above object, the invention described in claim 1 is provided with fuel injection means (6) for injecting fuel into the combustion chamber of the internal combustion engine (1), and compressing the air-fuel mixture in the combustion chamber to compress the fuel. In a control device for an internal combustion engine that burns fuel, state detection means for detecting an operating state (TE, TOIL, TW ) of the engine including exhaust temperature of the engine, and fuel injection control for controlling the fuel injection means (6) means and, in the idling state of the engine, when the detected operating state satisfies a predetermined condition by said state detecting means, and operation control means for changing the operating parameters of the engine (NINJ, CAIM), said engine Cetane number estimating means for estimating the cetane number (CET) of the fuel in use according to the ignition timing (CAFM) of the fuel detected after the operation parameter is changed; And when the predetermined condition is satisfied, the operation control means sets the fuel injection number (CINJ) to one and advances the fuel injection timing (CAIM), and the predetermined condition is the exhaust temperature ( It includes a condition that TE) is equal to or higher than a predetermined temperature (TE0) .

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect , the wall surface temperature (TWALL) of the combustion chamber in the idle operation state is within a predetermined temperature range (TWALL <TWLTH). Wall surface temperature condition determining means for determining a temperature condition is further provided, wherein the predetermined condition includes the wall surface temperature condition.

According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the second aspect , the wall surface temperature condition determining means is configured to determine an initial wall surface temperature (TWALL) based on an engine operation state immediately before shifting to the idle operation state. ), And gradually decreasing means for gradually decreasing the initial wall temperature (TWALL) after the engine operating state shifts to the idle operating state, and is output from the gradually decreasing means. When the temperature is within the predetermined temperature range, it is determined that the wall surface temperature condition is satisfied.

According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the second aspect , the wall surface temperature condition determining means is based on an initial wall surface temperature (TWALL) based on an engine operation state immediately before shifting to the idle operation state. ) And a waiting time (TWAIT) from when the engine operation state shifts to the idle operation state until the wall surface temperature condition is satisfied, according to the initial wall surface temperature (TWALL). Standby time setting means for setting the wall surface temperature, and determining that the wall surface temperature condition is satisfied when the standby time (TWAIT) has elapsed since the transition to the idle operation state.

  Further, it is preferable that the operation control means further reduces the target engine speed and / or decreases the intake air amount in the predetermined low load operation state when the predetermined condition is satisfied.

According to a fifth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to fourth aspects, the operation control means is configured to perform the fuel injection timing ( when the predetermined condition is satisfied ). CAIM) is set so that the difference in actual ignition timing (ΔCACET) resulting from the difference in cetane number is equal to or greater than a predetermined value (ΔCATH).

The invention according to claim 6, in the control apparatus for an internal combustion engine according to claim 5, wherein the fuel injection control means, when the predetermined condition is satisfied, before Ki燃 charge injection timing (CAIM), The engine is characterized in that a hydrocarbon emission amount (THC) of the engine is set to be equal to or less than a predetermined amount (THCLH).

The invention according to claim 7, in the control apparatus for an internal combustion engine according to claim 6, wherein the fuel injection control means, when the predetermined condition is satisfied, before Ki燃 charge injection timing (CAIM), A crank angle range of 20 to 25 degrees before the crank angle at which the piston corresponding to the combustion chamber reaches top dead center is set.

According to the invention described in claim 1, in the idle operating state of the engine, when the detected engine operation state satisfies a predetermined condition, changes the engine operating parameter is detected after the change of the engine operating parameters The cetane number of the fuel in use is estimated according to the ignition timing of the fuel. Specifically, since the number of times of fuel injection is one and the fuel injection timing is advanced, it is possible to accurately detect a delay in the ignition timing, and the amount of change in the ignition timing due to the difference in cetane number growing. As a result, the cetane number can be accurately estimated even when the engine is idling , and the cetane number of the fuel in use can be determined quickly and accurately. Also, if the number of fuel injections is one, the amount of hydrocarbons (HC) in the exhaust tends to increase as compared with the case where multiple injections are performed, and the exhaust gas recirculation control valve is stuck or the exhaust system catalytic converter is clogged. However, such a problem can be avoided by including in the predetermined condition that the exhaust temperature is equal to or higher than the predetermined temperature.

According to the second aspect of the present invention, the wall surface temperature condition that the wall surface temperature of the combustion chamber in the idling state is within a predetermined temperature range is determined, and at least the wall surface temperature condition is satisfied. Is done. When a high load operation is performed immediately before shifting to the idle operation state, the combustion chamber wall surface temperature becomes high, and the ignition timing is shifted in the advance direction from the normal time, so that an accurate cetane number cannot be estimated. By including the wall surface temperature condition in the predetermined condition, such a problem can be avoided and accurate cetane number estimation can be performed.

According to the third aspect of the present invention, the initial wall surface temperature is estimated based on the engine operation state immediately before shifting to the idle operation state, and after the engine operation state shifts to the idle operation state, the initial wall surface temperature is gradually increased. By reducing, the estimated wall surface temperature in the idle operation state can be obtained. When the estimated wall surface temperature is within the predetermined temperature range, it is determined that the wall surface temperature condition is satisfied. Therefore, the wall surface temperature condition can be accurately determined according to the engine operation state immediately before shifting to the idle operation state.

According to the invention described in claim 4, the initial wall temperature is estimated based on the engine operating state immediately before the transition to an idle operating state, the wall temperature condition is satisfied from the time when the engine operation state has shifted to idling Is set according to the initial wall surface temperature, and it is determined that the wall surface temperature condition is satisfied when the standby time has elapsed since the transition to the idle operation state. If the elapsed time after the transition to the idle operation state reaches the set standby time, the wall surface temperature is considered to be within the predetermined temperature range, so the wall surface temperature condition depends on the engine operation state immediately before the transition to the idle operation state. Can be accurately determined.

According to the fifth aspect of the present invention, when the predetermined condition is satisfied , the fuel injection timing is set so that the difference in the actual ignition timing due to the difference in cetane number is not less than the predetermined value. Accurate cetane number estimation can be performed.

According to the sixth aspect of the present invention, when the predetermined condition is satisfied , the fuel injection timing is set so that the hydrocarbon emission amount of the engine is equal to or less than the predetermined amount. Therefore, it is possible to prevent the exhaust characteristics from deteriorating.

According to the seventh aspect of the present invention, when the predetermined condition is satisfied , the fuel injection timing is set to a crank angle range 20 degrees to 25 degrees before the crank angle at which the piston reaches the top dead center. In addition, it is possible to accurately estimate the cetane number while suppressing hydrocarbon emissions.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
1 and 2 are diagrams showing the configuration of an internal combustion engine and a control device therefor according to an embodiment of the present invention. The following description will be given with reference to both figures together. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 6 is provided in each cylinder. The fuel injection valve 6 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 4, and the opening timing and opening time of the fuel injection valve 6, that is, the fuel injection timing and the fuel injection time are determined by the ECU 4. Controlled by

  The engine 1 includes an intake pipe 7, an exhaust pipe 8, and a turbocharger 9. The turbocharger 9 includes a turbine that is rotationally driven by the kinetic energy of the exhaust, and a compressor that is connected to the turbine via a shaft. The turbocharger 9 pressurizes (compresses) air sucked into the engine 1.

  An intercooler 21 is provided on the downstream side of the compressor of the intake pipe 7, and a throttle valve 22 is provided on the downstream side of the intercooler 21. The throttle valve 22 is configured to be opened and closed by an actuator 23, and the actuator 23 is connected to the ECU 4. The ECU 4 controls the opening degree of the throttle valve 22 via the actuator 23.

  Between the exhaust pipe 8 and the intake pipe 7, an exhaust gas recirculation passage 25 that recirculates exhaust gas to the intake pipe 7 is provided. The exhaust gas recirculation passage 25 is provided with an exhaust gas recirculation valve (hereinafter referred to as “EGR valve”) 26 for controlling the exhaust gas recirculation amount. The EGR valve 26 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 4. The EGR valve 26 is provided with a lift sensor 27 for detecting the valve opening degree (valve lift amount) LACT, and the detection signal is supplied to the ECU 4. The exhaust gas recirculation passage 25 and the EGR valve 26 constitute an exhaust gas recirculation mechanism.

  The intake pipe 7 includes an intake air amount sensor 31 that detects an intake air amount GA, a boost pressure sensor 32 that detects an intake pressure (supercharge pressure) PB on the downstream side of the compressor, and an intake pressure that detects an intake pressure PI. A sensor 33 is provided, and the exhaust pipe 8 is provided with an exhaust temperature sensor 34 for detecting the exhaust temperature TE. These sensors 31 to 34 are connected to the ECU 4, and detection signals of the sensors 31 to 34 are supplied to the ECU 4.

On the downstream side of the turbine of the exhaust pipe 8, a catalytic converter 28 that promotes oxidation of hydrocarbons and the like contained in the exhaust gas, and a particulate matter filter 29 that collects particulate matter (mainly composed of soot). Is provided.
Each cylinder of the engine 1 is provided with an in-cylinder pressure sensor 2 that detects an in-cylinder pressure (combustion pressure). In the present embodiment, the in-cylinder pressure sensor 2 is configured integrally with a glow plug provided in each cylinder. A detection signal from the in-cylinder pressure sensor 2 is supplied to the ECU 4. The detection signal of the in-cylinder pressure sensor 2 actually corresponds to a differential signal with respect to the crank angle (time) of the in-cylinder pressure PCYL, and the in-cylinder pressure PCYL is obtained by integrating the in-cylinder pressure sensor output. .

  The engine 1 is provided with a crank angle position sensor 3 that detects a rotation angle of a crankshaft (not shown). The crank angle position sensor 3 generates a pulse every crank angle, and the pulse signal is supplied to the ECU 4. The crank angle position sensor 3 further generates a cylinder identification pulse at a predetermined crank angle position of the specific cylinder and supplies it to the ECU 4.

  The ECU 4 detects an accelerator sensor 35 that detects an operation amount AP of an accelerator pedal of a vehicle driven by the engine 1, a cooling water temperature sensor 36 that detects a cooling water temperature TW of the engine 1, and a temperature TOIL of the lubricating oil of the engine 1. An oil temperature sensor 37, an oxygen concentration sensor (not shown) for detecting the oxygen concentration in the exhaust, an intake air temperature sensor (not shown) for detecting the intake air temperature TA of the engine 1, and the like are connected. The detection signal is supplied to the ECU 4.

  The ECU 4 supplies a control signal for the fuel injection valve 6 provided in the combustion chamber of each cylinder of the engine 1 to the drive circuit 5. The drive circuit 5 is connected to the fuel injection valve 6, and supplies a drive signal corresponding to the control signal supplied from the ECU 4 to the fuel injection valve 6. Thus, at the fuel injection timing corresponding to the control signal output from the ECU 4, fuel is injected into the combustion chamber of each cylinder by the fuel injection amount corresponding to the control signal. The ECU 4 normally executes pilot injection and main injection (double injection) for one cylinder.

  The ECU 4 includes an amplifier 10, an A / D converter 11, a pulse generator 13, a CPU (Central Processing Unit) 14, a ROM (Read Only Memory) 15 that stores a program executed by the CPU 14, and a CPU 14. A RAM (Random Access Memory) 16 for storing calculation results and the like, an input circuit 17, and an output circuit 18 are provided. A detection signal of the in-cylinder pressure sensor 2 is input to the amplifier 10. The amplifier 10 amplifies an input signal. The signal amplified by the amplifier 10 is input to the A / D converter 11. The pulse signal output from the crank angle position sensor 3 is input to the pulse generator 13.

  The A / D conversion unit 11 includes a buffer 12, converts the in-cylinder pressure sensor output input from the amplifier 10 into a digital value (hereinafter referred to as “pressure change rate”) dp / dθ, and stores the converted value in the buffer 12. More specifically, the A / D converter 11 is supplied with a pulse signal PLS1 (hereinafter referred to as “1 degree pulse”) PLS1 having a crank angle of 1 degree from the pulse generator 13, and this 1 degree pulse PLS1. The in-cylinder pressure sensor output is sampled at a period of

  On the other hand, the pulse signal PLS6 with a crank angle of 6 degrees is supplied from the pulse generator 13 to the CPU 14, and the CPU 14 performs a process of reading the digital value stored in the buffer 12 with the period of the 6 degrees pulse PLS6. . That is, in this embodiment, the A / D conversion unit 11 does not issue an interrupt request to the CPU 14, but the CPU 14 performs a reading process at a cycle of the 6-degree pulse PLS6.

  The input circuit 17 converts detection signals from various sensors into digital values and supplies them to the CPU 14. The engine speed NE is calculated from the cycle of the 6-degree pulse PLS. Further, the required torque TRQ of the engine 1 is calculated according to the accelerator pedal operation amount AP.

  The CPU 14 outputs a control signal for controlling the throttle valve 22, the EGR valve 26 and the like through the output circuit 18 in accordance with the engine operating state. Further, the CPU 14 executes processing for estimating the cetane number of the fuel in use as described below, and performs fuel injection control according to the estimated cetane number.

  FIG. 3 is a flowchart showing a procedure of cetane number estimation processing. In step S11, it is determined whether or not the engine 1 is in an idle state. If the answer is affirmative (YES), whether or not a predetermined execution condition for stably executing the cetane number estimation is satisfied. Is determined. The predetermined execution condition is, for example, that the exhaust temperature TE is equal to or higher than a predetermined temperature TE0 (for example, about 90 ° C.), and the cooling water temperature TW or the oil temperature TOIL indicating the warm-up state of the engine 1 is equal to or higher than the predetermined temperature TWUP (for example, 80 ° C.). It is established when

  If the answer to step S11 or S12 is negative (NO), the process immediately ends without performing cetane number estimation. When the predetermined execution condition is satisfied in step S12, the pilot injection is stopped and single injection is performed (step S13). That is, the number of fuel injections NINJ per cylinder is set to 1, and the main injection timing is changed from the normal to the advance direction (step S14). As described above, by making the fuel injection as single injection, the fuel injection timing is advanced from the normal time, so that it is possible to easily detect the difference in ignition timing due to the difference in cetane number.

  In step S15, a CAFMM map (not shown) is searched according to the engine speed NE and the required torque TRQ to calculate a reference ignition timing CAFMM. The CAFMM map is set based on, for example, fuel having a high cetane number (for example, 57). In step S16, the ignition delay angle DCA is calculated by subtracting the actual ignition timing CAFM from the reference ignition timing CAFMM.

  FIG. 4 is a block diagram showing a configuration of an ignition timing calculation module that calculates (detects) the actual ignition timing CAFM. The function of the ignition timing calculation module is realized by arithmetic processing by the CPU 14. The ignition timing calculation module includes a band pass filter unit 71, a phase delay correction unit 72, and an ignition timing determination unit 73. The band change filter unit 71 receives the pressure change rate dp / dθ output from the in-cylinder pressure sensor 2. A waveform W1 shown in FIG. 5 indicates an input waveform, and a waveform W2 indicates an output waveform. Since the phase delay occurs in the band pass filter unit 71, the phase delay correction unit 72 corrects this delay.

  The ignition timing determination unit 73 determines the crank angle position at which the pressure change rate dp / dθ has a peak value as the actual ignition timing CAFM, corresponding to the fuel injection. Specifically, as shown in FIG. 6B, the crank angle at which the pressure change rate dp / dθ output from the phase delay correction unit 72 exceeds the detection threshold DPP is determined as the actual ignition timing CAFM.

  FIG. 6A shows an injection pulse INJM starting from the crank angle CAIM, and FIG. 6B shows an angle range RDET (for example, 10 degrees) for detecting the actual ignition timing CAFM. Yes. Thus, by limiting the detection angle range RDET to a relatively narrow range, it is possible to accurately determine the ignition timing without increasing the calculation load on the CPU 14.

  Returning to FIG. 3, in step S17, the ignition delay angle DCA is converted into the ignition delay time TDFM using the engine speed NE, the CET table shown in FIG. 7 is searched according to the ignition delay time TDFM, and the cetane number CET Is calculated.

  According to the processing of FIG. 3, when the predetermined execution condition is satisfied in the idle operation state, the fuel injection is changed from the double injection to the single injection, and the fuel injection timing is changed in the advance direction. The cetane number can be estimated even in the operating state, and the cetane number of the fuel in use can be determined quickly and accurately.

  FIG. 11 is a graph showing the transition of the heat release rate HRR in a specific cylinder of the engine 1, where the solid line corresponds to fuel with a high cetane number (for example 57) and the broken line represents fuel with a low cetane number (for example 41). Correspond. The horizontal axis is the crank angle CA (when the piston is at the compression top dead center, it is set to “0” degree). FIG. 6A corresponds to the case where pilot injection and main injection are performed. In this case, fuel injection is performed in the vicinity of a crank angle of 0 degrees (compression top dead center), and 5 to 10 after top dead center. The heat release rate HRR reaches a peak at a degree. The difference in peak position due to the difference in cetane number is about 1 degree. FIG. 6B corresponds to the case where only the main injection is executed by advancing the fuel injection timing. In this case, the fuel injection is performed near a crank angle of −20 degrees (20 degrees before compression top dead center). The heat release rate HRR reaches a peak at 5 to 10 degrees before top dead center. The difference in peak position due to the difference in cetane number is about 8 degrees. That is, by making the fuel injection only the main injection (single injection) and advancing the injection timing, the difference in the ignition timing due to the difference in cetane number becomes more remarkable, and the calculation accuracy of the cetane number CET can be improved. .

  In addition, when performing single injection, the amount of hydrocarbon (HC) in the exhaust gas tends to increase compared to when performing multiple injections, and the EGR valve 26 is stuck or the catalytic converter 28 is easily clogged. In the process of FIG. 3, such a problem can be avoided by including in the predetermined execution condition that the exhaust temperature TE is equal to or higher than the predetermined temperature TE0.

  In this embodiment, the fuel injection valve 6 corresponds to the fuel injection means, the exhaust temperature sensor 34, the cooling water temperature sensor 36, and the oil temperature sensor 37 correspond to the state detection means, and the ECU 4 controls the fuel injection control means and the operation control. And cetane number estimating means. Specifically, fuel injection control (not shown) by the ECU 4 corresponds to fuel injection control means, steps S13 and S14 in FIG. 3 correspond to operation control means, and steps S14 to S17 correspond to cetane number estimation means. To do. In-cylinder pressure sensor 2 and ECU 4 correspond to actual ignition timing detection means.

(Modification 1)
FIG. 8 is a flowchart showing a modified example of the processing of FIG. 3 described above. In this process, step S21 is added between steps S14 and S15. In step S21, other operation parameters are changed. Specifically, any one, any two, or all three of the following processes 1) to 3) are executed:
1) Decrease the target engine speed in the idling state by about 100 rpm, for example.
2) Control the throttle valve 22 in the valve closing direction to reduce the amount of intake air.
3) The EGR valve 26 is closed.

By changing to these operating parameters, the difference in actual ignition timing CAFM due to the difference in cetane number increases, and the estimation accuracy of the cetane number can be improved.
When executing the process 2), the throttle valve 22 is closed so that the detected intake air amount GA becomes a desired value, or the throttle valve opening TH is detected, and the detected throttle valve opening is detected. The throttle valve 22 is closed so that the degree TH becomes a predetermined opening degree.

  FIG. 9A is a diagram showing the relationship between the intake air amount GA and the actual ignition timing CAFM. A rectangular point corresponds to a fuel having a cetane number of 41 and a circular point corresponds to a fuel having a cetane number of 57. To do. When the intake air amount GA is the first value GA1, the difference in the ignition timing is about 6 degrees, but by reducing the intake air amount GA to the second value GA2, the difference in the ignition timing is 10 degrees. Can be increased to a degree.

Further, by closing the EGR valve 26 and stopping the exhaust gas recirculation, a decrease in the cetane number estimation accuracy due to the air-fuel ratio error can be avoided, and the estimation accuracy can be improved.
Step S21 added in this modification corresponds to a part of the operation control means.

(Modification 2)
You may make it add immediately after refueling to the predetermined execution conditions in step S12. That is, if it is not immediately after refueling, cetane number estimation may not be performed, but cetane number estimation may be performed only immediately after refueling. Immediately after refueling is determined based on the increase in the fuel meter, the opening / closing of the filler cap, and the change of the engine switch from OFF to ON.

In this modification, a sensor (not shown) for determining that it is immediately after refueling is included in the state detection means.
Note that the exhaust temperature TE, the cooling water temperature TW, or the oil temperature TOIL may be excluded from the predetermined execution condition, and only immediately after refueling may be set as the predetermined execution condition.

(Modification 3)
In the case of an engine that does not include the throttle valve 22, the amount of intake air cannot be reduced by the throttle valve 22 in the first modification. Therefore, in step S21, either or both of the following 1) and 2) are performed. Execute:
1) Decrease the target engine speed in the idling state by about 100 rpm, for example.
2) The EGR valve 26 is controlled in the valve opening direction to reduce the intake air amount GA.

  FIG. 9B is a diagram showing the relationship between the intake air amount GA and the actual ignition timing CAFM. A rectangular point corresponds to a cetane number 41 fuel and a circular point corresponds to a cetane number 57 fuel. To do. When the intake air amount GA is the first value GA1, the difference in ignition timing is about 6 degrees, but by opening the EGR valve 26 and reducing the intake air amount GA to the second value GA2, The difference in ignition timing can be increased to about 8 degrees.

  In the present modification, the processing for executing one or both of the above 1) and 2) corresponds to a part of the operation control means.

[Second Embodiment]
If the cetane number estimation process described above is performed immediately after the high-load operation of the engine, the wall surface temperature of the combustion chamber is high, so that the estimation accuracy of the cetane number CET decreases. Therefore, in this embodiment, the cetane number estimation process is performed in consideration of the wall surface temperature of the combustion chamber.

  FIG. 12 shows the transition of the estimated cetane number CET when the cetane number estimation process described above is executed from time t0 when the cetane number of the fuel changes from the cetane number CETBF before refueling to the cetane number CETAF after refueling by refueling. Indicates. The solid line corresponds to the case where the wall surface temperature is low, not immediately after the high load operation, and the broken line corresponds to the case where the wall surface temperature is high immediately after the high load operation. As shown in this figure, the estimated cetane number CET gradually increases from the cetane number CETBF before refueling and almost coincides with the cetane number CETAF after refueling unless immediately after the high load operation. On the other hand, immediately after the high load operation, the fuel is easily ignited, so that the estimated cetane number CET is initially higher than the actual cetane number CETAF after refueling, and gradually converges to the cetane number CETAF after refueling. Go.

  Therefore, in the present embodiment, the cetane number estimation process is performed with one of the execution conditions that the wall surface temperature has decreased.

FIG. 13 is a flowchart showing a procedure of cetane number estimation processing in the present embodiment. This process is obtained by adding steps S31 to S34 to the process of FIG.
When the operating state of the engine 1 is not an idle state, an estimated wall surface temperature value (hereinafter simply referred to as “wall surface temperature”) TWALL of the combustion chamber is calculated in step S31. Specifically, the basic value is calculated according to the fuel injection amount TOUT and the engine speed NE, and the basic value is corrected according to the engine coolant temperature TW, the engine oil temperature TOIL, the exhaust gas temperature TE, and the intake air temperature TA. To calculate the wall surface temperature TWALL.

  When the operating state of the engine 1 shifts to the idle state, the process proceeds from step S11 to step S32, and it is determined whether or not the wall surface temperature TWALL is lower than a predetermined temperature TWLTH (for example, 100 ° C.). If this answer is affirmative (YES), the process proceeds to step S12.

  If TWALL ≧ TWLTH in step S32, the system waits for a predetermined time ΔTWAIT (for example, 30 seconds) (step S33), and decreases the wall surface temperature TWALL by the set decrease amount ΔT (step S34). Thereafter, the process returns to step S11. The setting decrease amount ΔT is set to a larger value as the wall surface temperature TWALL is higher.

  If Steps S32 to 34 are repeatedly executed and the answer to Step S32 is affirmative (YES), the process proceeds to Step S12. If the predetermined execution condition is satisfied in step S12, steps S13 to S17 are executed to calculate the estimated cetane number CET.

  According to the process of FIG. 13, when the engine 1 is in an operating state other than the idle state, the wall surface temperature TWALL is calculated, and is reduced by a predetermined decrease amount ΔT each time a predetermined time ΔTWAIT has elapsed after shifting to the idle state. . When the wall surface temperature TWALL becomes lower than the predetermined temperature TWLTH and the predetermined execution condition is satisfied, the cetane number is estimated. Therefore, when the state immediately shifts from the high load operation state to the idle state, the cetane number is not estimated until the wall surface temperature TWALL becomes lower than the predetermined temperature TWLTH. High estimation can be prevented and an accurate estimated cetane number CET can be calculated.

  In the present embodiment, step S31 of FIG. 13 corresponds to the initial wall surface temperature estimating means, step S34 corresponds to the gradually decreasing means, and steps S31 to S34 correspond to the wall surface temperature condition determining means.

(Modification)
FIG. 14 is a flowchart showing a modification of the process shown in FIG. In this process, steps S32 to S34 in FIG. 13 are deleted and steps S35 and S36 are added.

  In step S35, a TWAIT table (not shown) is searched according to the wall surface temperature TWALL, and a standby time TWAIT is calculated. The TWAIT table is set so that the standby time TWAIT becomes longer as the wall surface temperature TWALL becomes higher.

  When the engine 1 shifts to the idle state, the process proceeds to step S36, and it is determined whether or not the value of the upcount timer TIDL that measures the elapsed time from the transition to the idle state is equal to or longer than the standby time TWAIT. When the answer to step S11 is negative (NO), the process returns to step S11. When the value of the timer TIDL reaches the standby time TWAIT, the process proceeds to step S12.

  According to the process of FIG. 14, when the elapsed time after shifting to the idle operation state reaches the standby time TWAIT set according to the wall surface temperature TWALL, the wall surface temperature TWALL is lower than the predetermined temperature TWLTH. If the predetermined execution condition of step S12 is established, the estimated cetane number CET is calculated. Therefore, since the cetane number is not estimated until the wall surface temperature TWALL becomes lower than the predetermined temperature TWLTH, the cetane number of the fuel in use is prevented from being estimated to be higher than the actual, and an accurate estimated cetane number CET is calculated. be able to.

  In this modification, step S31 in FIG. 14 corresponds to the initial wall surface temperature estimating means, step S35 corresponds to the standby time setting means, and steps S31, S35, and S36 correspond to the wall surface temperature condition determining means.

[Fuel injection timing suitable for cetane number estimation]
Next, the fuel injection timing suitable for cetane number estimation will be described. FIG. 15 is a diagram showing the relationship between the fuel injection timing (main injection timing) CAIM and the HC (hydrocarbon) emission amount THC in single injection. As is clear from FIG. 6A, as the fuel injection timing CAIM is advanced, the HC emission amount THC increases. Therefore, the fuel injection timing CAIM is larger than −25 degrees (more retarded). It is desirable to set it to a value.

  As is clear from FIG. 5B, the HC emission amount THC increases when the fuel injection timing CAIM is further retarded from the top dead center (0 degree), so the fuel injection timing CAIM is more than 2 degrees. It is desirable to set a smaller (more advanced side) value.

  FIG. 16 is a diagram showing the relationship between the fuel injection timing CAIM and the actual ignition timing CAFM ′. The actual ignition timing CAFM 'is an actual ignition timing when the crank angle is defined so that the angle at which the piston is located at the top dead center is 0 degree and the advance direction is positive. Also, the circular points in the figure correspond to fuels with a cetane number of 54.5, and the rectangular points correspond to fuels with a cetane number of 40.5.

  On the advance side from −20 degrees shown in FIG. 9A, the difference in actual ignition timing CAFM ′ due to the difference in cetane number becomes large, and the cetane number can be accurately estimated. However, referring also to FIG. 5B, in the range from -20 degrees to 2 degrees, the difference in the actual ignition timing CAFM 'due to the difference in cetane number becomes small, and it is difficult to estimate the cetane number accurately.

  From the above, the fuel injection timing CAIM when estimating the cetane number is, as shown in FIG. 17, the HC emission amount THC is equal to or less than a predetermined amount THCLH (for example, 5 mg / sec) and actual ignition due to the difference in cetane number It is desirable to set a range R0 (−25 to −20 degrees) that is equal to or greater than a difference ΔCACET predetermined value ΔCATH (for example, 0.14 degrees / cetane number) of the timing CAFM ′. The ranges R1 and R2 shown in FIG. 17 correspond to a range where the HC emission amount THC increases, and the range R3 corresponds to a range where the difference in the actual ignition timing CAFM ′ due to the difference in cetane number decreases.

  By setting the fuel injection timing CAIM within the range R0 and performing cetane number estimation, it is possible to perform accurate estimation while suppressing the HC emission amount THC to be equal to or less than the predetermined amount THCLH. Such setting of the fuel injection timing CAIM is effective in both the first and second embodiments.

  In the above-described embodiment, the actual ignition timing CAFM is detected as the time when the pressure change rate dp / dθ detected by the in-cylinder pressure sensor 2 exceeds the detection threshold value DPP, but is not limited thereto. The crank angle position at which the heat generation rate is 50% of the maximum value may be determined as the ignition timing.

  Further, the cetane number estimation process may be executed only for at least one cylinder of the engine 1 and normal combustion may be continued in the other cylinders. In that case, the process shown in FIG. 3, FIG. 8, FIG. 13, or FIG. 14 is executed only for the cylinders that are the target of the cetane number estimation process.

Moreover, you may make it add determination (FIG. 13, step S31-S34, FIG. 14, step S31, S35, S36) of wall surface temperature conditions to the modifications 1-3 of 1st Embodiment.
The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. FIG. 2 is a diagram more specifically showing a partial configuration of the control device shown in FIG. 1. It is a flowchart which shows the procedure of the process which estimates the cetane number of the fuel in use. It is a block diagram which shows the structure of an ignition timing calculation module. It is a time chart for demonstrating the band pass filter process of an in-cylinder pressure sensor output. It is a time chart for demonstrating the detection method of ignition timing. It is a figure which shows the table for calculating a cetane number (CET) from ignition delay time (TDFM). It is a flowchart which shows the modification of the process shown in FIG. It is a figure which shows the relationship between intake air amount (GA) and ignition timing (CAFM). It is a figure which shows a premix combustion area | region. It is a figure which shows transition of the heat release rate (HRR) in a specific cylinder. It is a time chart for demonstrating a problem when a high load driving | running is performed before idle state transfer. It is a flowchart which shows the procedure of the cetane number estimation process concerning the 2nd Embodiment of this invention. It is a flowchart which shows the modification of the process shown in FIG. It is a figure which shows the relationship between fuel injection timing (CAIM) and HC discharge | emission amount (THC). It is a figure which shows the relationship between fuel-injection time (CAIM) and actual ignition timing (CAFM '). It is a figure for demonstrating the setting range (R0) of the fuel injection time suitable for cetane number estimation.

Explanation of symbols

1 Internal combustion engine 2 In-cylinder pressure sensor (actual ignition timing detection means)
4 Electronic control unit (fuel injection control means, operation control means, actual ignition timing detection means, cetane number estimation means, wall surface temperature condition determination means, initial wall surface temperature estimation means, gradual decrease means, standby time setting means)
6 Fuel injection valve (fuel injection means)
34 Exhaust temperature sensor (state detection means)
36 Cooling water temperature sensor (state detection means)
37 Oil temperature sensor (state detection means)

Claims (7)

In a control apparatus for an internal combustion engine comprising fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine, and combusting the fuel by compressing an air-fuel mixture in the combustion chamber,
State detecting means for detecting the operating state of the engine including the exhaust gas temperature of the engine,
Fuel injection control means for controlling the fuel injection means;
In the idle operating state of the engine, operating state detected by the state detecting means when a predetermined condition is satisfied, the operation control means for changing the operating parameters of the engine,
Cetane number estimation means for estimating the cetane number of the fuel in use according to the ignition timing of the fuel detected after the change of the engine operating parameter ,
When the predetermined condition is satisfied, the operation control means sets the number of fuel injections to 1 and advances the fuel injection timing,
The control apparatus for an internal combustion engine, wherein the predetermined condition includes a condition that the exhaust temperature is equal to or higher than a predetermined temperature . Wall surface temperature condition determining means for determining a wall surface temperature condition that the wall surface temperature of the combustion chamber in the idle operation state is within a predetermined temperature range,
The control apparatus for an internal combustion engine according to claim 1 , wherein the predetermined condition includes the wall surface temperature condition. The wall surface temperature condition determining means is an initial wall surface temperature estimating means for estimating an initial wall surface temperature based on an engine operation state immediately before shifting to the idle operation state, and after the engine operation state has shifted to the idle operation state, And a gradually decreasing means for gradually decreasing the initial wall surface temperature, and it is determined that the wall surface temperature condition is satisfied when a temperature output from the gradually decreasing means is within the predetermined temperature range. Item 3. A control device for an internal combustion engine according to Item 2 . The wall temperature condition determining means, and the initial wall temperature estimating means for estimating the initial wall temperature based on the engine operating state immediately before the transition to the idle operating state, from the time when the engine operating state is shifted to the idling Standby time setting means for setting a standby time until the wall surface temperature condition is satisfied according to the initial wall surface temperature, and when the standby time has elapsed since the transition to the idle operation state, the wall surface The control apparatus for an internal combustion engine according to claim 2 , wherein it is determined that the temperature condition is satisfied. Said operation control means, when the predetermined condition is satisfied, according to the fuel injection timing, the difference between the actual ignition timing due to the difference in the cetane number, characterized in that set to be equal to or greater than a predetermined value Item 5. The control device for an internal combustion engine according to any one of Items 1 to 4 . It said operation control means, when the predetermined condition is satisfied, the pre Ki燃 fuel injection timing, to claim 5, hydrocarbon emissions of the engine and sets to be equal to or less than a predetermined amount The internal combustion engine control device described. It said fuel injection control means, wherein when a predetermined condition is satisfied, the pre Ki燃 fuel injection timing, the crank angle of 25 degrees before the 20 degrees from the crank angle corresponding piston reaches the top dead center in the combustion chamber The control device for an internal combustion engine according to claim 6 , wherein the control device is set within a range.

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