JP5061972B2 - Control device for internal combustion engine and fuel property determination device - Google Patents

Description

  The present invention relates to an internal combustion engine control device and a fuel property determination device.

In an internal combustion engine, in order to realize stable combustion, it is necessary to control the fuel injection amount, the injection timing, etc. according to the properties of the fuel used. Therefore, a technique for determining the properties of the fuel used has been conventionally known. For example, Patent Document 1 includes pressure detection means for detecting the pressure in the combustion chamber and volume detection means for detecting the volume of the combustion chamber, and the combustion chamber is determined from the detected pressure in the combustion chamber and the volume of the combustion chamber. It is described that a heat generation amount parameter having a correlation with the heat generation amount is calculated and the cetane number of the fuel is measured based on the change of the heat generation amount parameter.
JP 2005-344550 A

  However, in the above conventional technique, it is necessary to detect the pressure in the combustion chamber by a relatively expensive in-cylinder pressure sensor or the like, but higher accuracy is required because it is necessary to detect a change in one cycle. In particular, problems remain in terms of cost.

  Accordingly, an object of the present invention is to determine the properties of the fuel used and maintain the combustion state of the internal combustion engine appropriately without using an expensive device such as an in-cylinder pressure sensor.

The present invention includes a control means for setting a control parameter related to the ignitability of fuel in a cylinder based on a temperature change of exhaust gas with respect to a timing of post-injection performed after main injection, and a control corresponding to the ignitability of fuel Set parameters.
Specifically, the first internal combustion engine control device according to the present invention detects the timing of post-injection when the temperature of the exhaust discharged from the engine changes from rising to decreasing by changing the timing of post-injection performed after the main injection. And a control means for setting a control parameter related to the ignitability of the fuel in the cylinder based on the detected post-injection timing, and the control parameter includes the timing of the preliminary injection performed before the main injection, Control parameters that correspond to the ignitability of the fuel, including at least one of the preliminary injection amount, main injection timing, starting fuel injection amount, supercharging pressure, intake air temperature, and fuel injection pressure. is there.

The control apparatus for a second internal combustion engine according to the present invention detects the timing of post-injection in which the amount of increase in the temperature of the exhaust gas that has passed through the exhaust purification catalyst exceeds a predetermined value by changing the timing of post-injection performed after the main injection. And control means for setting a control parameter related to the ignitability of the fuel in the cylinder based on the detected post-injection timing. The control parameter includes the timing of the preliminary injection performed before the main injection, the preliminary injection The control parameter is set according to the ignitability of the fuel, including at least one of the amount, the timing of the main injection, the fuel injection amount at the start, the supercharging pressure, the intake air temperature, and the fuel injection pressure.

In the present invention, the fuel property is determined based on the temperature change of the exhaust with respect to the timing of the post-injection performed after the main injection.
Specifically, the fuel property determination device for a first internal combustion engine according to the present invention changes the timing of post-injection performed after main injection, and the temperature of exhaust discharged from the engine reaches a peak on the high temperature side. The timing is detected, and the fuel property is determined based on the detected injection timing.

  The fuel property determination apparatus for a second internal combustion engine according to the present invention changes the timing of post-injection performed after main injection, and determines the timing of post-injection when the amount of increase in the temperature of exhaust gas that has passed through the exhaust purification catalyst exceeds a predetermined value. Then, the fuel property is determined based on the detected post-injection timing.

  If the fuel properties (ignitability, cetane number) are different, the temperature change of the exhaust with respect to the timing of post-injection will differ, more specifically, the post-injection in which the temperature of the exhaust discharged from the engine has a peak on the high temperature side It has been confirmed that the post-injection timing changes when the temperature rise of the exhaust gas that has passed through the exhaust purification catalyst exceeds the predetermined value.

  According to the present invention, based on the temperature change of the exhaust with respect to the timing of the post-injection performed after the main injection, more specifically, the time of the post-injection when the temperature of the exhaust discharged from the engine becomes a peak on the high temperature side, or Since control parameters related to the ignitability of fuel in the cylinder are set based on the timing of post-injection when the amount of increase in the temperature of the exhaust gas that has passed through the exhaust purification catalyst exceeds a predetermined value, an expensive device such as an in-cylinder pressure sensor Without using this, it is possible to set a control parameter corresponding to the fuel property being used to maintain the combustion state of the engine properly, and to determine the fuel property being used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an internal combustion engine (diesel engine) according to an embodiment of the present invention. In FIG. 1, an intake compressor 2 of the turbocharger 4 is provided in the intake passage 2 of the engine 1 on the downstream side of the air cleaner 3. The intake compressor 41 is coaxially coupled to an exhaust turbine 42 that is provided in the exhaust passage 5 and is rotationally driven by the energy of the exhaust. The turbocharger 4 includes an intake compressor 41, an exhaust turbine 42, and a variable nozzle 43, and the intake compressor 41 rotates as the exhaust turbine 42 rotates, so that air is compressed and sent. The variable nozzle 43 is driven via an actuator 44 by a control signal from an engine control unit (ECU) 10 to vary the turbine volume.

  An intercooler 6 is provided on the downstream side of the intake compressor 41. The intercooler 6 cools the air (supercharged air) compressed by the intake compressor 41. The supercharged air cooled by the intercooler 6 is further supplied to the combustion chamber of each cylinder of the engine 1 via the intake throttle valve 7, the collector portion 8 and the intake manifold 9 on the downstream side. The intake throttle valve 7 is driven via an actuator 71 by a control signal from the ECU 10.

In the exhaust passage 5, a diesel oxidation catalyst (corresponding to “exhaust purification catalyst” of the present invention, hereinafter referred to as “DOC”) 11 and a diesel particulate filter (hereinafter referred to as “DPF”) 12 are provided downstream of the exhaust turbine 42. Is intervening. The DOC 11 oxidizes HC and CO in the exhaust and generates NO ₂ , and the DPF 12 collects particulate matter (PM) in the exhaust gas discharged from the engine 1.

  An EGR cooler 14 and an EGR valve 15 are provided in the EGR passage 13 that connects the exhaust passage 5 upstream of the exhaust turbine 42 and the collector portion 8 of the intake passage 2. The EGR passage 13 is a passage that recirculates exhaust gas toward the intake side, and the EGR cooler 14 cools the exhaust gas that recirculates through the EGR passage 13. The EGR valve 15 is driven to open and close by a control signal from the ECU 10 and adjusts the recirculation amount of the exhaust gas to the intake side so that a predetermined EGR rate corresponding to the operating state is obtained.

  The engine 1 also includes a common rail combustion injection device 16. The fuel injection device 16 includes a supply pump 17, a common rail 18, and a fuel injection valve 19. The fuel pumped from the supply pump 17 is stored in the common rail 18. The supply pump 17 is controlled by the ECU 10 so that the fuel pressure in the common rail 18 becomes a predetermined pressure. The fuel injection valve 19 is driven to open by the ECU 10 and injects pressurized fuel supplied via the common rail 18 into the cylinder of each cylinder. This fuel injection device 16 (fuel injection valve 19) can divide and inject fuel, and specifically, performs a preliminary injection that injects a predetermined amount (a small amount) of fuel before the main injection. In addition, post-injection can be performed in which a predetermined amount (small amount) of fuel is injected after the main injection.

  The ECU 10 receives detection signals output from various sensors, and executes various controls based on these detection signals. In particular, the ECU 10 determines the fuel property in a steady operation state such as during idle operation, and sets each control parameter of the engine 1 based on the determination result.

  Here, as various sensors, an accelerator sensor 21 that detects an accelerator opening (depression amount), a crank angle sensor (also functions as an engine speed sensor) 22, a water temperature sensor 23 that detects an engine cooling water temperature, and intake air An air flow meter 24 for detecting the amount, a first temperature sensor (in the present embodiment, upstream of the exhaust turbine 42) provided on the upstream side of the DOC 11 and detecting the temperature of the exhaust gas discharged from the engine 1 (" (Corresponding to “upstream exhaust temperature detecting means”) 25, a second temperature sensor (detecting the inlet exhaust temperature of the DPF 12) provided downstream of the DOC 11 and detecting the exhaust temperature passing through the DOC 11 (in other words, the present invention) 26), a third temperature sensor 27 for detecting the outlet exhaust temperature of the DPF 12, and a differential pressure detection passage 28 for bypassing the DPF 12. It is in the like differential pressure sensor 29 for detecting a pressure difference between an upstream side and a downstream side of the DPF 12 (the pressure loss).

Next, control executed by the ECU 10 in a steady operation state such as during idle operation will be described. Here, the post-injection performed after the main injection intended for idling after the engine is started is mainly performed to raise the temperature of the exhaust gas. The temperature of the exhaust gas discharged from the engine 1 varies depending on the timing of post-injection (the injection amount is substantially constant). Normally, the later the timing of post-injection (the more retarded), the higher the temperature of the exhaust gas. However, if the timing of post-injection is further delayed, this time the temperature of the exhaust begins to decrease. This is because the in-cylinder temperature decreases as the working gas expands due to the lowering of the piston, so that the fuel injected later is not burned sufficiently and the temperature of the combustion gas decreases. That is, if the timing of post-injection is changed (to the retard side), the temperature of the exhaust gas changes from rising to lowering.

  On the other hand, the ignition delay of the fuel injected into the cylinder also changes depending on the ignitability of the fuel being used. When the ignitability of the fuel is good (that is, the cetane number is high), the ignition delay is short, and conversely, when the fuel ignitability is bad (that is, the cetane number is low), the ignition delay is long. That is, the worse the ignitability of the fuel, the longer the ignition delay becomes, and the in-cylinder temperature decreases due to the expansion of the working gas. Therefore, when using fuel with poor ignitability, the retarding limit of the timing of post-injection is lower than when using fuel with good ignitability, and the temperature of the exhaust is changed by changing the timing to post-injection. When (change) is monitored, the post-injection timing is advanced (advanced side) after the temperature of the exhaust gas changes from rising to decreasing.

FIG. 2 shows the relationship between the timing of post-injection (PoIT) and the temperature (Tex) of exhaust exhausted from the engine 1. In FIG. 2, the solid line indicates a case where a reference fuel (for example, a fuel widely distributed in the market) is used. In this case, the post-injection timing at which the exhaust gas temperature changes from rising to lowering, that is, the post-injection timing PoITp at which the exhaust gas temperature reaches the high temperature side is equivalent to CA1 (hereinafter referred to as “reference time” of the present invention. Reference time PoITp _ST ").

  On the other hand, when a fuel having lower ignitability than the reference fuel (lower cetane number) is used, as shown by the broken line, the post-injection timing PoITp at which the exhaust gas temperature reaches the high temperature side is higher than CA1. When the fuel has a better ignitability (higher cetane number) than that of the reference fuel, as shown by the alternate long and short dash line, the post-injection temperature at which the exhaust gas temperature reaches the high temperature side is shown. The timing PoITp is CA3 that is retarded from CA1.

  Therefore, the temperature of the exhaust gas is monitored by changing the timing of the post-injection, and the timing of the post-injection when the exhaust gas temperature changes from rising to lowering, that is, the exhaust gas temperature reaches a peak on the high temperature side (actually, it is almost The fuel with good ignitability and the fuel with poor ignitability can be distinguished by the post-injection timing PoITp.

  Therefore, in the first embodiment of the present invention, the timing of the post-injection performed after the main injection is changed to detect the post-injection timing PoITp at which the temperature of the exhaust discharged from the engine 1 becomes a peak on the high temperature side, Based on the detected post-injection timing PoITp, the fuel properties (ignitability, cetane number) are determined, and control parameters related to the in-cylinder ignitability of the injected fuel (hereinafter simply referred to as “control parameters”). ) To maintain the combustion state of the engine 1 properly regardless of the properties of the fuel used (ignitability, cetane number).

FIG. 3 is a flowchart of a fuel property determination and control parameter setting routine according to the first embodiment, which is executed during idle operation after engine startup.
In FIG. 3, in step S1, post-injection is performed in which a predetermined amount of fuel is injected at a predetermined time PoIT _n after the main injection. The post-injection performed here may be performed for the present control, or may be performed for the purpose of raising the temperature of the exhaust gas to activate the DOC11.

In step S2, the exhaust temperature Tex _n detected by the first temperature sensor 25 after a predetermined time ts1 from the post-injection is read. Here, the predetermined time ts1 is set in consideration of the time during which the post-injected fuel burns.

In step S3, the post-injection timing PoIT _n and the exhaust gas temperature Tex _n detected in step S2 are recorded.
In step S4, the timing of post-injection is retarded by a predetermined amount set in advance. As a result, the post-injection performed next time is executed after a predetermined time later than the post-injection performed this time.

In step S5, post-injection is performed at the retarded timing POIT _{n + 1} .
In step S6, as in step S2, the exhaust temperature Tex _{n + 1} detected by the first temperature sensor 25 is read after a predetermined time ts1 from the post-injection executed in step S5.

In step S7, the retarded post-injection timing PoIT _{n + 1} and the exhaust gas temperature Tex _{n + 1} detected in step S6 are recorded.
In step S8, the calculated difference between the temperature Tex _n of exhaust gas by post-injection temperature _{Tex n + 1} and the previous exhaust gas by after this injection ΔTex a _{(= Tex n + 1 -Tex n} ).

In step S9, it is determined whether or not ΔTex (= Tex _{n + 1} −Tex _n ) is smaller than a predetermined value DTex (≦ 0). If ΔTex ≧ DTex, the process proceeds to step S10, PoIT _{n + 1} is set to PoIT _n , Tex _{n + 1 is set} to Tex _n , and the process returns to step S4. Then, Steps S4 to S9 are repeated, and when ΔTex <DTex, the process proceeds to Step S11. As a result, it is determined that the temperature change of the exhaust gas discharged from the engine 1 has changed from rising to lowering by retarding the timing of post-injection.

  In step S11, the timing of post-injection after the temperature of the exhaust gas changes from rising to lowering, that is, the timing of post-injection PoITp when the temperature of the exhaust gas reaches a peak on the high temperature side is detected (see FIG. 2).

  In step S12, the fuel properties (ignitability, cetane number) are determined based on the post-injection timing PoITp detected in step S11. Specifically, the relationship between the post-injection timing PoITp at which the temperature of the exhaust gas reaches a substantially high temperature side and the cetane number of the fuel is obtained in advance and a table as shown in FIG. 4 is created and detected in step S11. The cetane number of the fuel is determined by referring to this table based on the post-injection timing PoITp. In addition, you may progress to following step S12, without determining a fuel property in this step S12.

In step S13, a control parameter is set based on the post-injection timing PoITp detected in step S11.
As described above, the post-injection timing PoITp at which the exhaust gas temperature reaches a peak on the high temperature side changes depending on the ignitability of the fuel, and the earlier the worse the ignitability, the more advanced the ignitability. Slow (retard side).

  Therefore, control parameters are set so as to ensure stable ignition of the fuel injected mainly by the main injection according to the post-injection timing PoITp detected in step S11. Specifically, as the post-injection timing PoITp detected in step S11 is on the advance side, it is determined that the ignitability of the fuel being used is poor, and ignition failure and ignition delay are prevented to prevent injection fuel from being injected. Control parameters are controlled to ensure stable ignition.

  Here, the control parameters include the timing of preliminary injection performed before the main injection, the preliminary injection amount, the supercharging pressure, the starting fuel injection amount, the main injection timing, and the fuel injection pressure (fuel pressure in the common rail 18). The control parameters are set by referring to tables as shown in FIGS. Basically, as the post-injection timing PoITp detected in step S11 is on the advance side, the in-cylinder temperature is increased, the starting fuel injection amount is increased, the main injection timing is advanced, and the fuel injection timing is increased. Increase injection pressure (fuel pressure in common rail 18).

  Note that it is not necessary to set all the control parameters, and any one or a combination thereof may be used. Further, as will be apparent from the following description, the control parameter is set by correcting the control parameter, that is, correcting the basic value of each control parameter based on the post-injection timing PoITp detected in step S11. Is also included.

  First, preliminary injection timing (FIG. 5), preliminary injection amount (FIG. 6), and supercharging pressure (FIG. 7) as control parameters will be described. These are set mainly to increase or decrease the in-cylinder temperature during main injection.

As shown in FIG. 5, the preliminary injection timing PiIT is set to an advance side as the post-injection timing PoITp detected in step S11 is on the advance side. This is because even if fuel with poor ignitability is used, preliminary combustion is surely performed before main injection to increase the in-cylinder temperature and prevent ignition delay of fuel due to main injection. More specifically, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _{ST, the} preliminary injection timing PiIT _ST (that is, normally set based on the operating state) (ie, , Which is a preliminary injection timing adapted to the reference fuel, and is set to an advance side with respect to the "basic preliminary injection timing"). Conversely, the post-injection timing PoITp detected in step S11 is the reference timing. when in the retard side than PoITp _ST it is set to the retard side with respect to the basic pre-injection timing PiIT _ST.

Here, a correction amount is calculated with reference to a table or the like based on the deviation ΔPoIT between the post-injection timing PoITp detected in step S11 and the reference timing PoITp _ST, and the basic preliminary injection timing is corrected with the calculated correction amount. It is good also as composition to do. In this case, when the post-injection timing PoITp detected in step S11 is on the advance side of the reference time PoITp _ST , the preliminary injection timing is corrected, and when it is on the retard side, the preliminary injection timing is retarded. It will be corrected.

As shown in FIG. 6, the preliminary injection amount QPi is set to increase as the post-injection timing PoITp detected in step S11 is on the advance side. This is because the in-cylinder temperature at the time of main injection accompanying the preliminary combustion is increased or decreased by increasing or decreasing the preliminary injection amount QPi. More specifically, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _{ST, the} preliminary injection amount QPi _ST (that is, normally set based on the operating state) (ie, The preliminary injection amount QPi which is a preliminary injection amount adapted to the reference fuel and is hereinafter referred to as “basic preliminary injection amount”) is set. Conversely, the post-injection timing PoITp detected in step S11 is the reference timing. When it is on the retard side with respect to PoITp _ST , a preliminary injection amount QPi smaller than the basic preliminary injection amount QPi _ST is set.

Of course, similarly to the preliminary injection timing, a correction amount is calculated with reference to a table or the like based on the deviation ΔPoIT between the post-injection timing PoITp detected in step S11 and the reference timing PoITp _ST, and the calculated correction amount Thus, the basic preliminary injection amount may be corrected. In this case, when the post-injection timing PoITp detected in step S11 is on the advance side with respect to the reference time PoITp _ST , the preliminary injection amount is corrected to be increased, and when it is on the retard side, the preliminary injection amount is corrected to be decreased. Become.

As shown in FIG. 7, the supercharging pressure Pc is set higher as the post-injection timing PoITp detected in step S11 is on the advance side. This is because the in-cylinder temperature is increased or decreased by increasing or decreasing the supercharging pressure Pc. More specifically, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _{ST, the} supercharging pressure Pc _ST (hereinafter referred to as “basic supercharging” set during normal operation). In contrast, when the post-injection timing PoITp detected in step S11 is on the more retarded side than the reference timing PoITp _ST , the basic supercharging pressure Pc _{ST is set.} A lower supercharging pressure is set.

Also for this supercharging pressure, a correction amount is calculated with reference to a table or the like based on the difference ΔPoIT between the post-injection timing PoITp and the reference timing PoITp _ST detected in step S11, and the basic supercharging pressure Pc is calculated with this correction amount. _It is good also as a structure which correct _| amends _ST . In this case, when the post-injection timing PoITp detected in step S11 is on the advance side with respect to the reference time PoITp _{ST, the} boost pressure is corrected to increase, and when it is on the retard side, the boost pressure is corrected to decrease. Become.

Here, as a method other than the above, the in-cylinder temperature may be increased by increasing the temperature of the intake air flowing into the cylinder. Although not shown, for example, in FIG. 1, a bypass passage that bypasses the intercooler 6 and an on-off valve that opens and closes the bypass passage (variable cross-sectional area of the passage) are provided, and the post-injection timing detected in step S11 When PoITp is more advanced than the reference time PoITp _ST, the opening of the on-off valve is adjusted according to the deviation ΔPoIT so that a part of the supercharged air passes through the bypass passage. Similarly, an EGR bypass passage that bypasses the EGR cooler 14 and an opening / closing valve that opens and closes the EGR bypass passage (variable in the cross-sectional area of the passage) are provided, and the post-injection timing PoITp detected in step S11 is the reference time. When it is on the more advanced side than PoITp _ST, the opening of the on-off valve is adjusted according to the deviation ΔPoIT so that a part of the EGR gas passes through the bypass passage. Further, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _ST , the EGR gas amount is increased in accordance with the deviation ΔPoIT. By executing any one or a combination of these, the temperature of the air (intake air) flowing into the cylinder can be increased, and thus the in-cylinder temperature can be increased.

Next, the starting fuel injection amount as a control parameter will be described.
As shown in FIG. 8, the starting fuel injection amount is set to increase as the post-injection timing PoITp detected in step S11 is on the advance side. This is because even when a fuel with poor ignitability is used, the starting can be performed more reliably. Note that the starting fuel injection amount set here is that at the next starting time. More specifically, when the post-injection timing PoITp detected in step S11 is more advanced than the reference timing PoITp _{ST, the} starting fuel injection amount that is normally set based on the engine coolant temperature (that is, The starting fuel injection amount adapted to the reference fuel, which is hereinafter referred to as “basic starting fuel injection amount”) is set, and conversely, the post-injection detected in step S11 When the timing PoITp is on the retarded side with respect to the reference timing PoITp _ST , the starting fuel injection amount with a small basic starting fuel injection amount is set.

Also for the starting fuel injection amount, a correction amount is calculated with reference to a table or the like based on the deviation ΔPoIT between the post-injection timing PoITp detected in step S11 and the reference timing PoITp _ST. The fuel injection amount may be corrected. In this case, when the post-injection timing PoITp detected in step S11 is on the advance side with respect to the reference time PoITp _{ST, the} fuel injection amount at the start is increased and corrected (the increase at the start is further increased), and the retarded side When it is, the fuel injection amount at start-up is corrected to decrease (the increase at start-up is decreased).

Further, the timing of main injection as a control parameter will be described.
As shown in FIG. 9, the main injection timing IT is set to an advance side as the post injection timing PoITp detected in step S11 is on the advance side. For fuels with poor ignitability, the main injection is performed early in consideration of the ignition delay period, and the injected fuel is ignited at an appropriate time, while for fuels with good ignitability, the pre-ignition is delayed by delaying the main injection. This is to prevent the above. More specifically, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _{ST, the} main injection timing IT _ST that is normally set based on the operating state or the like (ie, , The main injection timing adapted to the reference fuel, which is hereinafter referred to as “basic main injection timing”) is set, and the post injection timing detected in step S11 is conversely set. When PoITp is on the retard side with respect to the reference time PoITp _ST , the main injection timing on the retard side with respect to the basic main injection timing IT _ST is set.

Also for the main injection timing, a correction amount is calculated with reference to a table or the like based on the deviation ΔPoIT between the post-injection timing PoITp and the reference timing PoITp _ST detected in step S11, and the basic main timing is calculated based on the calculated correction amount. It is good also as composition which corrects injection timing. In this case, when the post-injection timing PoITp detected in step S11 is on the advance side of the reference time PoITp _ST , the main injection timing is corrected, and when it is on the retard side, the main injection timing is delayed. The angle will be corrected.

Furthermore, the fuel injection pressure (fuel pressure in the common rail 18) Pf as a control parameter is set higher as the post-injection timing PoITp detected in step S11 is on the advance side, as shown in FIG. The This is to suppress ignition delay and shorten the combustion period to ensure stable combustion. More specifically, when the post-injection timing PoITp detected in step S11 is on the more advanced side than the reference timing PoITp _{ST, the} injection pressure Pf _ST (hereinafter, “basic” If the injection pressure higher than (the injection pressure) is set, and the post-injection timing PoITp detected in step S11 is on the more retarded side than the reference timing PoITp _ST , the injection pressure is higher than the basic injection pressure Pf _ST . A low injection pressure is set.

Also for this injection pressure Pf, a correction amount is calculated with reference to a table or the like based on the deviation ΔPoIT between the post-injection timing PoITp and the reference timing PoITp _ST detected in step S11, and the basic injection pressure is calculated using this calculated correction amount. A configuration may be adopted in which _PfST is corrected. In this case, when the post-injection timing PoITp detected in step S11 is on the advance side with respect to the reference time PoITp _ST , the injection pressure is corrected to increase, and when it is on the retard side, the injection pressure is corrected to decrease. .

  In the present embodiment, the timing of post-injection performed after the main injection is changed to detect the timing of post-injection PoITp at which the temperature of the exhaust discharged from the engine 1 has a substantially high temperature peak (S1 to S11). Based on the detected post-injection timing PoITp, fuel properties (ignitability, cetane number) are determined (S12), and control parameters are set or corrected (S13). Thereby, the property (cetane number) of the fuel used can be determined without using an expensive device such as an in-cylinder pressure sensor, and the combustion state of the engine can be properly maintained regardless of the property of the fuel used. Moreover, since the property determination of the fuel used and the setting (correction) of the control parameter are performed every time the engine 1 is started, stable combustion of the engine 1 can be more effectively maintained.

  If the post-injection timing in step S1 in FIG. 3 is sufficiently retarded, the post-injection timing may be advanced in step S4. It is possible to detect the post-injection timing PoITp at which the exhaust gas temperature reaches a peak on the high temperature side.

In the above description, each control parameter is corrected when the post-injection timing PoITp detected in step S11 is on the advance side or on the retard side with respect to the reference time PoITp _ST . Instead of the reference time PoITp _ST , the post-injection timing PoITp detected in step S11 is on the advance side or on the retard side from the post-injection time PoITp (-1) detected at the previous start. At some time, each control parameter may be corrected. In this case, the correction amount of each control parameter may be calculated on the basis of the previous value, and the change amount of each control parameter associated with the correction can be reduced.

Next, fuel property determination and control parameter setting according to the second embodiment will be described.
In this embodiment, the timing of the post-injection performed after the main injection is changed to detect the timing of the post-injection in which the amount of increase in temperature (including the rate of increase) of the exhaust gas that has passed through the DOC 11 exceeds a predetermined value. Based on the timing of post-injection, fuel properties (ignitability, cetane number) are determined, and control parameters related to the in-cylinder ignitability of the injected fuel (hereinafter simply referred to as “control parameters”) are set. Thus, the combustion state of the engine 1 is kept appropriate regardless of the properties of the fuel used (ignitability, cetane number).

  It should be noted that the timing of the post-injection in which the amount of increase in the temperature of exhaust gas that has passed through the DOC 11 (including the rate of increase) detected in the present embodiment exceeds a predetermined value is exhausted from the engine 1 detected in the first embodiment. Therefore, in the following explanation, the timing of the post-injection in which the amount of increase in the temperature of the exhaust gas that has passed through the DOC11 exceeds a predetermined value Is also represented by “PoITp”.

  As described above, when the post-injection timing is retarded, the post-injected fuel is not sufficiently burned. When sufficient combustion is not performed in the cylinder, HC and CO in the exhaust discharged from the engine 1 increase, and the amount of oxidation reaction in the DOC 11 also increases. Due to this oxidation reaction, the temperature of the exhaust gas that has passed through DOC11, that is, the outlet temperature of DOC11, increases.

  And the worse the ignitability of the fuel, the longer the ignition delay becomes, and the later injected fuel tends to be in a state where it cannot be burned sufficiently. For this reason, when a fuel with poor ignitability is used, the outlet temperature of the DOC 11 starts to rise faster than when a fuel with good ignitability is used (on the advance side).

FIG. 11 shows the relationship between the post-injection timing (PoIT) and the outlet temperature (TCout) of the DOC11. In FIG. 11, the solid line indicates a case where a reference fuel (for example, a fuel widely distributed in the market) is used. In this case, when the post-injection timing is gradually retarded, the post-injection timing TCout of the DOC11 begins to increase rapidly, that is, the amount of increase in the outlet temperature TCout of the DOC11 exceeds the predetermined value. The time PoITp is CA1 (corresponding to the “reference time” of the present invention, and hereinafter referred to as “reference time PoITp _ST ”).

  On the other hand, when a fuel having lower ignitability (lower cetane number) than the reference fuel is used, as shown by a broken line, the post-injection timing PoITp at which the increase in the outlet temperature of the DOC 11 exceeds a predetermined value is When fuel is used which has a lead angle of CA2 than CA1 and has better ignitability (higher cetane number) than the reference fuel, as shown by the alternate long and short dash line, the amount of increase in the outlet temperature of the DOC11 reaches a predetermined value. The post-injection timing PoITp that exceeds this time is CA3 that is retarded from CA1.

  Accordingly, the outlet temperature of the DOC 11 is monitored by changing the timing of the post-injection, and the timing of the post-injection when the outlet temperature starts to rise rapidly, that is, the timing of the post-injection PoITp when the amount of increase in the outlet temperature exceeds a predetermined value Thus, it is possible to distinguish between a fuel with good ignitability and a fuel with poor ignitability.

  Therefore, in the present embodiment, the timing of the post-injection performed after the main injection is changed to detect the timing of the post-injection in which the outlet temperature of the DOC 11 rapidly increases, and the fuel property is determined based on the detected timing of the post-processing. Judgment is made and control parameters are set.

FIG. 12 is a flowchart of a fuel property determination and control parameter setting routine according to the second embodiment, which is executed during idle operation after engine startup.
In FIG. 12, in step S21, as in step S1 of FIG. 3, post-injection is performed in which a predetermined amount of fuel is injected at a predetermined time PoIT _n after the main injection.

In step S22, the exhaust temperature (DOC outlet temperature) TCout _n detected by the second temperature sensor 26 after a predetermined time ts2 from the post-injection is read. Here, the predetermined time ts2 (> ts1) is set in consideration of the time until the exhaust of the post-injected fuel reaches the DOC11.

In step S23, the post-injection timing PoIT _n and the DOC outlet temperature TCout _n detected in step S22 are recorded.
In step S24, as in step 4 of FIG. 3, the post-injection timing is retarded by a predetermined amount.

In step S25, post-injection is performed at the retarded timing POIT _{n + 1} .
In step S26, as in step S22, the DOC outlet temperature TCout _{n + 1} detected by the second temperature sensor 26 after a predetermined time ts2 from the post injection executed in step S25 is read.

In step S27, the retarded post-injection timing PoIT _{n + 1} and the DOC outlet temperature TCout _{n + 1} detected in step S26 are recorded.
At step S28, it calculates the difference (increase _{amount) ΔTCout (= TCout n + 1} -TCout n) of the DOC outlet temperature TCOUT _{n + 1} due to the injection after the time the DOC outlet temperature TCOUT _n by injection after the previous. Note that the rate of increase (TCout _{n + 1} / TCout _n ) may be calculated instead of the amount of increase.

In step S29, it is determined whether or not ΔTCout (= TCout _{n + 1} −TCout _n ) is larger than a predetermined value DTCout. The predetermined value DTCout is a value for determining that the DOC outlet temperature has rapidly increased, and is determined in advance by experiments or the like. If ΔTCout ≦ DTCout, the process proceeds to step S30, PoIT _{n + 1} is set to PoIT _n , TCout _{n + 1} is set to TCout _n , and the process returns to step S24. Then, Steps S24 to S29 are repeated, and when ΔTCout> DTCout, the process proceeds to Step S31. As a result, it is determined that the DOC outlet temperature has rapidly increased by retarding the timing of post-injection.

  In step S31, a post-injection timing at which ΔTCout> DTCout, that is, a post-injection timing PoITp in which the amount of increase in the DOC outlet temperature exceeds a predetermined value is detected (see FIG. 11).

  In step S32, the fuel properties (ignitability, cetane number) are determined with reference to the table shown in FIG. 4 based on the post-injection timing PoITp detected in step S31. Since the determination of the fuel property is the same as that in the first embodiment, the description thereof is omitted (see the description of step S12 in FIG. 3). Further, as in the first embodiment, the process may proceed to the next step S33 without determining the fuel property in this step S32.

  In step S33, each control parameter is set with reference to the tables shown in FIGS. 5 to 10 based on the post-injection timing PoITp detected in step S31. Since the setting of each control parameter is the same as that in the first embodiment, the description thereof is omitted (see the description of step 13 in FIG. 3).

  In this embodiment, the timing of post-injection performed after the main injection is changed to detect the post-injection timing PoITp at which the temperature rise of the exhaust gas that has passed through the DOC 11 exceeds a predetermined value (S21 to S31). Based on the post-injection timing PoITp, the fuel properties (ignitability, cetane number) are determined (S32), and control parameters are set or corrected (S33). Thereby, also by this embodiment, the effect similar to the said 1st Embodiment can be acquired.

  Also in the present embodiment, when the post-injection timing in step S21 is sufficiently retarded, the post-injection timing may be advanced in step S24. It is possible to detect the post-injection timing PoITp in which the amount of increase in the temperature of the exhaust gas that has passed through exceeds a predetermined value.

Furthermore, also in the present embodiment, each control parameter is corrected when the post-injection timing PoITp detected in step S31 is on the advance side or on the retard side with respect to the reference time PoITp _ST . However, instead of the reference time PoITp _ST , the post-injection timing PoITp detected in step S31 is more advanced or retarded than the post-injection timing PoITp (-1) detected at the previous start. In this case, each control parameter may be corrected. In this case, the correction amount of each control parameter may be calculated on the basis of the previous value, and the change amount of each control parameter associated with the correction can be reduced.

1 is an overall configuration diagram of an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the relationship between the timing (PoIT) of post-injection, and the temperature (Tex) of the exhaust gas discharged | emitted from an engine. 4 is a flowchart of a fuel property determination and control parameter setting routine according to the first embodiment. It is a figure which shows an example of the table which determines a fuel property (cetane number). It is a figure which shows an example of the table which sets the timing of the preliminary injection as a control parameter. It is a figure which shows an example of the table which sets the preliminary injection amount as a control parameter. It is a figure which shows an example of the table which sets the supercharging pressure as a control parameter. It is a figure which shows an example of the table which sets the fuel injection quantity at the time of a start as a control parameter. It is a figure which shows an example of the table which sets the time of the main injection as a control parameter. It is a figure which shows an example of the table which sets the injection pressure of the fuel as a control parameter. It is a figure which shows the relationship between the timing (PoIT) of post-injection, and the exit temperature (TCout) of DOC (diesel oxidation catalyst). 7 is a flowchart of a fuel property determination and control parameter setting routine according to a second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 4 ... Turbocharger, 5 ... Exhaust passage, 7 ... Intake throttle valve, 10 ... ECU (control means), 11 ... DOC (exhaust purification catalyst), 16 ... Fuel injection device (fuel injection means) , 17 ... Supply pump, 18 ... Common rail, 19 ... Fuel injection valve, 23 ... Water temperature sensor, 24 ... Air flow meter, 25 ... First temperature sensor (upstream exhaust temperature detecting means), 26 ... Second temperature sensor (downstream side) Exhaust temperature detection means), 29 ... Differential pressure sensor

Claims (21)

Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
An exhaust temperature detecting means provided in the exhaust passage of the engine for detecting the temperature of the exhaust;
Control means for setting a control parameter for setting a control parameter related to the ignitability of the fuel in the cylinder based on a temperature change of the exhaust with respect to a timing of post-injection performed after main injection;
With
The control parameter is at least one of a timing of preliminary injection performed before the main injection, a preliminary injection amount, a timing of the main injection, a starting fuel injection amount, a supercharging pressure, an intake air temperature, and a fuel injection pressure. And setting the control parameter corresponding to the ignitability of the fuel . Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
An upstream side exhaust temperature detecting means provided on the upstream side of the exhaust purification catalyst interposed in the exhaust passage of the engine and detecting the temperature of the exhaust discharged from the engine;
The timing of the post-injection performed after the main injection is changed to detect the timing of the post-injection when the temperature of the exhaust gas discharged from the engine has changed from rising to lowering, and based on the detected timing of the subsequent injection, Control means for setting a control parameter related to the ignitability of the fuel in
With
The control parameter is at least one of a timing of preliminary injection performed before the main injection, a preliminary injection amount, a timing of the main injection, a starting fuel injection amount, a supercharging pressure, an intake air temperature, and a fuel injection pressure. And setting the control parameter corresponding to the ignitability of the fuel . Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
A downstream side exhaust temperature detecting means provided on the downstream side of the exhaust purification catalyst interposed in the exhaust passage of the engine and detecting the temperature of the exhaust gas that has passed through the exhaust purification catalyst;
The timing of the post-injection performed after the main injection is changed to detect the timing of the post-injection in which the amount of increase in the temperature of the exhaust gas that has passed through the exhaust purification catalyst exceeds a predetermined value, and based on the detected timing of the post-injection Control means for setting control parameters related to the ignitability of fuel in the cylinder;
With
The control parameter is at least one of a timing of preliminary injection performed before the main injection, a preliminary injection amount, a timing of the main injection, a starting fuel injection amount, a supercharging pressure, an intake air temperature, and a fuel injection pressure. And setting the control parameter corresponding to the ignitability of the fuel . 4. The control unit according to claim 1, wherein the control means advances at least one of the preliminary injection timing and the main injection timing as the detected post-injection timing is on the advance side. A control device for an internal combustion engine according to claim 1. When the detected post-injection timing is on the advance side with respect to a preset reference timing, the control means performs at least the advance correction of the preliminary injection timing and the advance correction of the main injection timing. The control apparatus for an internal combustion engine according to claim 4, wherein one is performed. When the detected post-injection timing is on the retard side with respect to a preset reference timing, the control means performs at least a delay angle correction of the preliminary injection timing and a delay angle correction of the main injection timing. 6. The control apparatus for an internal combustion engine according to claim 4, wherein one of the operations is performed. The control means detects the timing of the post-injection every time the engine is started,
When the detected post-injection timing is more advanced than the previously detected post-injection timing, at least one of the advance injection correction of the preliminary injection timing and the advance correction of the main injection timing is performed. The control apparatus for an internal combustion engine according to claim 4. The control means detects the timing of the post-injection every time the engine is started,
When the detected post-injection timing is more retarded than the previously detected post-injection timing, at least one of the preliminary injection timing delay correction and the main injection timing delay correction is performed. 8. The control apparatus for an internal combustion engine according to claim 4, wherein the control apparatus is an internal combustion engine . The control means increases at least one of the preliminary injection amount and the starting fuel injection amount at the next start as the detected post-injection timing is on the advance side. 8. The control device for an internal combustion engine according to any one of 7 above. The control means performs at least one of an increase correction of the preliminary injection amount and an increase correction of the fuel injection amount at start-up when the detected post-injection timing is on the advance side with respect to a preset reference timing. 10. The control device for an internal combustion engine according to claim 9, wherein the control device is performed. The control means performs at least one of the preliminary injection amount reduction correction and the start-up fuel injection amount reduction correction when the detected post-injection timing is on the retarded side with respect to a preset reference timing. The control device for an internal combustion engine according to claim 9 or 10, wherein the control device is performed. The control means detects the timing of the post-injection every time the engine is started,
When the detected post-injection timing is more advanced than the previously detected post-injection timing, at least one of the preliminary injection amount increase correction and the start-up fuel injection amount increase correction is performed. The control device for an internal combustion engine according to claim 9. The control means detects the timing of the post-injection every time the engine is started,
When the detected post-injection timing is more retarded than the previously detected post-injection timing, at least one of the preliminary injection amount reduction correction and the start-up fuel injection amount reduction correction is performed. The control apparatus for an internal combustion engine according to claim 9 or 12. The control means increases at least one of the supercharging pressure and the injection pressure as the detected post-injection timing is on the advance side. The control apparatus of the internal combustion engine described in 1. The control means performs at least one of the correction correction for the boost pressure and the correction correction for the injection pressure when the detected post-injection timing is on the advance side with respect to a preset reference timing. The control apparatus for an internal combustion engine according to claim 14. The control means performs at least one of the correction correction for the supercharging pressure and the correction correction for the injection pressure when the detected post-injection timing is on the retard side with respect to a preset reference timing. 16. The control apparatus for an internal combustion engine according to claim 14 or 15, characterized in that: The control means detects the timing of the post-injection every time the engine is started,
The boost pressure increase correction and the injection pressure increase correction are performed when the detected post-injection timing is more advanced than the previously detected post-injection timing. Item 15. The control device for an internal combustion engine according to Item 14. The control means detects the timing of the post-injection every time the engine is started,
The boost pressure reduction correction or the injection pressure reduction correction is performed when the detected post-injection timing is more retarded than the previously detected post-injection timing. Item 18. The control device for an internal combustion engine according to item 14 or claim 17. Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
An exhaust temperature detecting means provided in the exhaust passage of the engine for detecting the temperature of the exhaust;
Fuel property determination means for determining combustion property based on a temperature change of the exhaust with respect to a timing of post-injection performed after main injection;
A fuel property determination apparatus for an internal combustion engine, comprising: Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
An upstream side exhaust temperature detecting means provided on the upstream side of the exhaust purification catalyst interposed in the exhaust passage of the engine and detecting the temperature of the exhaust discharged from the engine;
The timing of post-injection performed after the main injection is changed to detect the timing of post-injection when the temperature of the exhaust gas discharged from the engine has changed from rising to lowering, and the fuel property is determined based on the detected timing of post-injection. Fuel property determining means for determining
A combustion property determination device for an internal combustion engine, comprising: Fuel injection means capable of dividing and injecting fuel into the cylinder of the engine;
A downstream flow side exhaust temperature detecting means provided on the downstream side of the exhaust purification catalyst interposed in the exhaust passage of the engine and detecting the temperature of the exhaust gas that has passed through the exhaust purification catalyst;
The timing of the post-injection performed after the main injection is changed to detect the timing of the post-injection in which the increase in the temperature of the exhaust gas that has passed through the exhaust purification catalyst exceeds a predetermined value. Based on the detected timing of the post-injection Fuel property determining means for determining the fuel property;
A combustion property determination device for an internal combustion engine, comprising:

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