JP2010077832A - Fuel property determining device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel property determining device for an internal combustion engine that accurately determines the property of fuel supplied to the internal combustion engine. <P>SOLUTION: The operating state of a diesel engine 10 is detected (Step 100). An exhaust gas air-fuel ratio is controlled to ABYF1 (Step 102). Rich spike is executed (Step 104). An A/F peak amount ΔPABYF1 is obtained (Step 106). The exhaust gas air-fuel ratio is controlled to ABYF2 (Step 108). Rich spike is executed (Step 110). An A/F peak amount ΔPABYF2 is obtained (Step 112). A deviation ΔP (=ΔPABYF1-ΔPABYF2) is calculated (Step 114). The fuel property (T90) is determined according to a map defining the relation of the deviation ΔP and the fuel property T90 (Step 116). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel property determination device for an internal combustion engine that determines the property of fuel supplied to the internal combustion engine.

  Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 2007-187094, in catalyst bed temperature control when the internal combustion engine is cold, a fuel property is determined by comparing a parameter value calculated from an air-fuel ratio with a reference value. Devices are known to do. In this apparatus, in the catalyst bed temperature control at the time of cold start, the air-fuel ratio is transiently changed to lean by retarding the ignition timing. The lean degree varies depending on the amount of fuel attached to the port or the like, that is, the fuel evaporability. For this reason, the property of the fuel can be determined based on the parameter calculated from the lean air-fuel ratio.

JP 2007-187094 A JP 2006-161788 A

  However, when the fuel evaporative parameter is detected based on only a specific condition as in the above-described conventional apparatus, the detected value includes various errors due to factors such as individual differences in engine performance and sensor deterioration. It will be superimposed. Therefore, the conventional apparatus for determining the fuel property by comparing the detected value with the predetermined value may not be able to accurately determine the fuel property.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a fuel property determination device for an internal combustion engine that can accurately determine the property of fuel supplied to the internal combustion engine. To do.

In order to achieve the above object, a first invention is a fuel property determination apparatus for an internal combustion engine,
Air-fuel ratio control means for controlling the air-fuel ratio of the exhaust gas of the internal combustion engine to a control target air-fuel ratio;
An air-fuel ratio detecting means provided in an exhaust passage of the internal combustion engine for detecting the air-fuel ratio;
Exhaust flow rate control means for controlling the flow rate of exhaust gas (hereinafter referred to as exhaust flow rate);
Rich spike means for temporarily changing the air-fuel ratio to a richer side than the control target air-fuel ratio;
Change of the air-fuel ratio when the rich spike means is executed under a situation where the exhaust flow rate is a predetermined exhaust flow rate, and the rich spike means is executed under a situation where the exhaust flow rate is different from the predetermined exhaust flow rate Determination means for determining a fuel property of the fuel supplied to the internal combustion engine based on the change in the air-fuel ratio in the case;
It is characterized by providing.

According to a second invention, in the first invention,
The air-fuel ratio control means controls the air-fuel ratio to the control target air-fuel ratio by changing the exhaust flow rate using the exhaust flow rate control means.

According to a third invention, in the second invention,
The determination means includes
A deviation between the peak of the air-fuel ratio and the first air-fuel ratio (hereinafter referred to as a first air-fuel ratio deviation) when the rich spike means is executed in a situation where the control target air-fuel ratio is a predetermined first air-fuel ratio. First computing means for computing
Deviation between the peak of the air-fuel ratio and the second air-fuel ratio when the rich spike means is executed under the condition that the control target air-fuel ratio is a predetermined second air-fuel ratio richer than the first air-fuel ratio. (Hereinafter, the second air-fuel ratio deviation) is calculated, and
The fuel property of the fuel of the internal combustion engine is determined based on the first air-fuel ratio deviation and the second air-fuel ratio deviation.

According to a fourth invention, in the third invention,
The determination means includes third calculation means for calculating a deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation, and determines the fuel property based on a comparison between the deviation and a predetermined value. It is characterized by that.

According to a fifth invention, in the third invention,
The determination means calculates a ratio (hereinafter referred to as a first ratio) of a deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation with respect to a deviation between the first air-fuel ratio and the second air-fuel ratio. The fuel property is determined based on a comparison between the first ratio and a predetermined value.

A sixth invention is the invention according to any one of the third to fifth inventions,
A temperature control means for controlling the temperature of the exhaust gas;
The exhaust gas temperature when the control target air-fuel ratio is the first air-fuel ratio is controlled to be lower than that when the control target air-fuel ratio is the second air-fuel ratio.

A seventh invention is the sixth invention, wherein
The determination means includes the first air-fuel ratio deviation with respect to the deviation between the temperature of the exhaust gas when the control target air-fuel ratio is the first air-fuel ratio and the temperature of the exhaust gas when the control target air-fuel ratio is the second air-fuel ratio. Including a fifth calculating means for calculating a ratio of the deviation from the second air-fuel ratio deviation (hereinafter referred to as a second ratio), and determining the fuel property based on a comparison between the second ratio and a predetermined value. It is characterized by.

According to an eighth invention, in any one of the first to seventh inventions,
The rich spike means includes a fuel injection valve provided in the exhaust passage on the upstream side of the air-fuel ratio detection means, and injects a predetermined amount of fuel into the exhaust passage from the fuel injection valve. .

  According to the first aspect of the invention, the air-fuel ratio when the means (rich spike) for temporarily changing the exhaust air-fuel ratio to the rich side from the control target air-fuel ratio is executed under the condition that the exhaust gas flow rate is the predetermined exhaust flow rate. The fuel property of the fuel supplied to the internal combustion engine is determined based on the change and the air-fuel ratio change when the rich spike is executed under a situation where the exhaust flow rate is different from the predetermined exhaust flow rate. Here, in the air-fuel ratio change due to the rich spike, a steady error component due to individual differences between devices, deterioration over time, or the like, that is, an error component that does not depend on the properties of the fuel or the exhaust flow rate is superimposed. According to the present invention, since the error component can be canceled based on the air-fuel ratio change under different exhaust flow conditions, compared with the case where the fuel property is determined simply by the air-fuel ratio change at one exhaust flow rate. The determination accuracy can be effectively improved.

  According to the second invention, the exhaust gas flow rate can be controlled by controlling the air-fuel ratio of the exhaust gas.

  According to the third aspect of the invention, the deviation (air-fuel ratio deviation) between the peak of the air-fuel ratio and the control target air-fuel ratio when the rich spike means is executed under the condition where the air-fuel ratio is controlled to each control target air-fuel ratio. Each is calculated. These air-fuel ratio deviations directly reflect the influence of fuel properties in each air-fuel ratio environment (each exhaust flow rate environment). Therefore, according to the present invention, the fuel property can be accurately determined based on these air-fuel ratio deviations.

  According to the fourth aspect of the invention, the fuel property is determined based on a comparison between the deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation and a predetermined value. Each air-fuel ratio deviation is superposed with a steady error component caused by individual differences in the apparatus, aging deterioration, or the like. Therefore, according to the present invention, the error component can be canceled by calculating the deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation. Therefore, by comparing the deviation with a predetermined value, The fuel property can be accurately determined.

  According to the fifth aspect of the present invention, the ratio of the deviation (first ratio) between the first air-fuel ratio deviation and the second air-fuel ratio deviation with respect to the deviation between the first air-fuel ratio and the second air-fuel ratio is compared with a predetermined value. Based on this, the fuel property is determined. In the first ratio, a steady error component superimposed on each air-fuel ratio deviation is cancelled. In addition, there is no restriction on the selection of the control target air-fuel ratio in the calculation of the first ratio. For this reason, according to the present invention, the degree of freedom in selecting the air-fuel ratio is increased, so that an appropriate air-fuel ratio can be appropriately set according to the fuel to be used.

  The lower the temperature of the exhaust gas, the lower the evaporability of the rich spike introduced into the exhaust passage. For this reason, the lower the temperature of the exhaust gas, the more easily the difference in evaporability due to the fuel appears. According to the sixth aspect of the invention, the exhaust temperature when the rich spike is performed at the first air-fuel ratio is controlled to be lower than that at the second air-fuel ratio. For this reason, according to this invention, the determination precision of a fuel property can be improved effectively.

  According to the seventh aspect, the ratio of the deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation with respect to the deviation between the exhaust temperature at the first exhaust flow rate and the exhaust temperature at the second exhaust flow rate (second ratio). ) And a predetermined value, the fuel property is determined. There is a certain correlation between the second ratio and the fuel properties. Therefore, according to the present invention, it is possible to accurately determine the fuel property based on the relationship.

  According to the eighth aspect of the invention, the rich spike means is realized by injecting fuel into the exhaust gas into the exhaust passage. Therefore, according to the present invention, rich spike can be implemented with a simple configuration without performing special air-fuel ratio control.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a schematic configuration of an internal combustion engine system as a first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes a four-cycle diesel engine 10 having a plurality of cylinders (four cylinders in FIG. 1). It is assumed that the diesel engine 10 is mounted on a vehicle and is used as a power source for the vehicle.

  Each cylinder of the diesel engine 10 is provided with an injector 12 for directly injecting fuel into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the diesel engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port (not shown) of each cylinder. An exhaust turbine of the turbocharger 24 is connected to the downstream side of the exhaust passage 18. A post-processing device 26 for purifying exhaust gas is provided further downstream of the turbocharger 24 in the exhaust passage 18. As the post-processing device 26, for example, an oxidation catalyst, a NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or the like can be used.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air drawn through the air cleaner 30 is compressed by the intake compressor of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by an intake manifold 34 to intake ports (not shown) of each cylinder.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. One end of an exhaust gas recirculation (EGR) passage 40 is connected to the vicinity of the intake manifold 34 in the intake passage 28. The other end of the EGR passage 40 is connected to the vicinity of the exhaust manifold 20 in the exhaust passage 18. In this system, a part of the exhaust gas (burned gas) can be recirculated to the intake passage 28 through the EGR passage 40. Hereinafter, the exhaust gas recirculated to the intake passage 28 through the EGR passage 40 is referred to as “EGR gas”.

  An EGR cooler 42 for cooling the EGR gas is provided in the middle of the EGR passage 40. An EGR valve 44 is provided downstream of the EGR cooler 42 in the EGR passage 40. By changing the opening degree of the EGR valve 44, the amount of exhaust gas passing through the EGR passage 40, that is, the EGR amount can be adjusted.

  The exhaust manifold 20 of the diesel engine 10 is provided with an exhaust injection injector 46 for injecting fuel into the exhaust gas exhausted from the exhaust port. The exhaust injector 46 can make the air-fuel ratio of the exhaust gas temporarily excessive (rich) than the control target air-fuel ratio by supplying excess fuel (rich spike) to the exhaust gas. Further, an A / F sensor 52 for detecting an air-fuel ratio (A / F) of the exhaust gas is installed on the upstream side of the aftertreatment device 26 in the exhaust passage 18.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 50 as shown in FIG. In addition to the A / F sensor 52 described above, various sensors for controlling the diesel engine 10 are connected to the input unit of the ECU 50. In addition to the injector 12, the intake throttle valve 36, the EGR valve 44, and the exhaust injection injector 46 described above, various actuators for controlling the diesel engine 10 are connected to the output portion of the ECU 50. The ECU 50 drives each device in accordance with a predetermined program based on various types of input information.

[Operation of Embodiment 1]
Next, characteristic operations in the system of the present embodiment will be described. In the diesel engine 10 of the present embodiment, the opening degree of the EGR valve 44 is feedback-controlled so that the exhaust air-fuel ratio detected by the A / F sensor 52 becomes a predetermined control target air-fuel ratio. More specifically, for example, when the exhaust air-fuel ratio is changed in the lean direction without changing the fuel injection amount, the EGR gas amount is reduced. As a result, since the ratio of fresh air sucked into the diesel engine 10 increases, the flow rate of exhaust gas exhausted into the exhaust passage 18 (hereinafter referred to as “exhaust flow rate”) changes in a direction in which the amount increases. . On the other hand, when the exhaust air-fuel ratio is changed in the rich direction, the EGR gas is increased. Thereby, since the ratio of fresh air decreases, the exhaust gas flow rate changes in a direction of decreasing.

  Here, in the diesel engine 10 of the present embodiment, when a rich spike is performed from the exhaust injection injector 46, the injected fuel flows through the exhaust passage 18 while evaporating (vaporizing) into the exhaust gas. For this reason, when the exhaust gas at the time of rich spike reaches the A / F sensor 52, the sensor output temporarily changes to the rich side with respect to the control target air-fuel ratio.

  FIG. 2 is a diagram illustrating a change in the A / F sensor output when the rich spike is performed. In this figure, a solid line L1 indicates a case where a highly evaporative fuel is used as the fuel of the diesel engine 10, and a one-dot chain line L2 indicates a case where a low evaporative fuel is used as the fuel. As shown in this figure, in each fuel, the deviation (hereinafter referred to as “A / F peak amount”) between the peak of the air-fuel ratio due to a rich spike (hereinafter referred to as “peak air-fuel ratio”) and the control target air-fuel ratio. In comparison, the A / F peak amount ΔPL2 of the low evaporative fuel is smaller than the A / F peak amount ΔPL1 of the high evaporative fuel. This is because the higher the evaporative fuel, the more actively the fuel evaporates in the process of circulating in the exhaust passage 18.

  Therefore, it is also conceivable to determine the fuel properties by comparing the A / F peak amount with a predetermined value. However, the A / F peak amount is not only influenced by the fuel properties, but also by the effects of stationary errors such as individual differences in the engine performance of the diesel engine 10 and output deviations caused by deterioration of various sensors. ing. For this reason, even if the A / F peak amount is simply compared with the predetermined value, the fuel property cannot be accurately determined.

  Here, a change in the A / F peak amount when the control target air-fuel ratio is changed will be considered. FIG. 3 is a diagram showing an exhaust air-fuel ratio curve when a rich spike is performed. In this figure, a solid line L3 and an alternate long and short dash line L4 indicate that the fuel of the diesel engine 10 is a highly evaporative fuel and a low evaporation when the control target air-fuel ratio is a predetermined first air-fuel ratio (for example, A / F = 30). The solid line L5 and the one-dot chain line L6 indicate the exhaust air / fuel ratio when using the basic fuel when the control target air / fuel ratio is the second air / fuel ratio (for example, A / F = 20) smaller than the first air / fuel ratio. The exhaust air-fuel ratio when high evaporative fuel and low evaporative fuel are used is shown.

  As shown in this figure, when the control target air-fuel ratio is the first air-fuel ratio, the A / F peak amount ΔPL4 of the low evaporative fuel is significantly smaller than the A / F peak amount ΔPL3 of the highly evaporative fuel. ing. The exhaust flow rate is related to the difference in the A / F peak amount. That is, as the control target air-fuel ratio is increased, that is, as the exhaust gas flow rate is increased, the time for the rich spike to reach the A / F sensor 52 is shortened. For this reason, with low evaporative fuel with low evaporability, the rich spike fuel reaches the A / F sensor 52 before it evaporates sufficiently, resulting in a large difference in the A / F peak amount. It becomes.

  On the other hand, when the control target air-fuel ratio is the second air-fuel ratio (<first air-fuel ratio), the difference between the A / F peak amount ΔPL5 of the highly evaporative fuel and the A / F peak amount ΔPL6 of the low evaporative fuel There are few. This is because when the control target air-fuel ratio is small, that is, when the exhaust gas flow rate is small, the time for the rich spike to reach the A / F sensor 52 becomes long. For this reason, even if it is a low evaporation fuel, evaporation is accelerated | stimulated and, as a result, the difference of A / F peak amount becomes small.

  Thus, the amount of change in the A / F peak amount when the control target air-fuel ratio is changed (hereinafter referred to as “deviation ΔP”) varies depending on the evaporation performance of the fuel used. FIG. 4 is a graph showing the relationship between the deviation ΔP of the A / F peak amount at the time of rich spike at different control target air-fuel ratios and the fuel property (T90). As shown in this figure, the deviation ΔP increases as the T90 of the fuel increases, that is, as the fuel is a low-evaporation fuel (heavy fuel). This indicates that a certain correlation exists between the deviation ΔP of the A / F peak amount and the fuel property (T90). Further, since the deviation ΔP is calculated as a deviation of each A / F peak amount, a steady error component superimposed on each A / F peak amount is canceled.

  Therefore, in the present embodiment, the property (for example, T90) of the fuel used in the diesel engine 10 is determined based on the deviation ΔP. More specifically, the deviation ΔP of the A / F peak amount at different control target air-fuel ratios is calculated. Then, the fuel property (T90) is determined based on the calculated deviation ΔP and the correlation shown in FIG. Thereby, since the influence of the steady error component superimposed on the A / F peak amount can be eliminated, the fuel property (T90) of the fuel supplied to the diesel engine 10 can be accurately determined. .

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 5, the specific content of the process performed in this Embodiment is demonstrated. FIG. 5 is a flowchart of a routine executed by the ECU 50 to determine the property (T90) of the supplied fuel.

  In the routine shown in FIG. 5, first, the operating condition of the diesel engine 10 is detected (step 100). Here, specifically, operating conditions such as the engine speed NE, the fuel injection amount TAU, the water temperature THW, and the like are detected.

  Next, the exhaust air-fuel ratio is controlled to ABYF1 (step 102). Specifically, the opening degree of the EGR valve 44 is feedback-controlled so that the exhaust air-fuel ratio detected by the A / F sensor 52 becomes ABYF1.

  If the exhaust air-fuel ratio is controlled to ABYF1 in step 102, then a rich spike is performed (step 104). Here, specifically, a predetermined amount of fuel is injected from the exhaust injector 46.

Next, an A / F peak amount ΔPABYF1 is acquired (step 106). Specifically, first, the peak air-fuel ratio PABYF1 is detected based on the output signal of the A / F sensor 52. Next, the A / F peak amount ΔPABYF1 is calculated according to the following equation (1).
ΔPABYF1 = PABYF1-ABYF1 (1)

  Next, the exhaust air-fuel ratio is controlled to ABYF2 (step 108). Next, a rich spike is performed (step 110). Next, an A / F peak amount ΔPABYF2 is acquired (step 112). Here, specifically, the same processing as in steps 102 to 106 is executed.

In the routine shown in FIG. 5, next, the deviation ΔP of the A / F peak amount is calculated (step 114). Specifically, ABYF1, ABYF2, and A / F peak amounts ΔPABYF1 and ΔPABYF2 detected in steps 106 and 112 are substituted into the following equation (2).
Deviation ΔP = ΔPABYF1−ΔPABYF2 (2)

  Next, the fuel property (T90) is determined (step 116). FIG. 6 shows a map defining the relationship between the deviation ΔP and T90 (° C.). As shown in this map, T90 has a larger value as the deviation ΔP of the A / F peak amount is larger. The ECU 50 stores a map shown in FIG. Specifically, T90 corresponding to the deviation ΔP calculated in step 114 is specified according to the map shown in FIG.

  As described above, according to the first embodiment, the fuel property (T90) can be determined based on the deviation ΔP of the A / F peak amount when the rich spike is performed in different exhaust air-fuel ratio environments. . As a result, the influence of the stationary error component superimposed on the sensor output can be eliminated, so that the fuel property (T90) of the fuel supplied to the engine can be accurately determined.

  By the way, according to Embodiment 1 mentioned above, although the fuel property of the fuel supplied to the diesel engine 10 is determined, the internal combustion engine to which the present invention is applied is not limited to the diesel engine. That is, a gasoline engine using gasoline as a fuel may be used, or another known internal combustion engine may be used.

  Further, according to the first embodiment described above, T90 is determined as the fuel property, but the fuel property that can be determined is not limited to T90. That is, if the relationship between the deviation ΔP of the A / F peak amount and other fuel properties (for example, T50) is stored in advance as a map, the same processing as the above processing is executed, so that other fuel properties are obtained. Can also be determined with high accuracy.

  Further, according to the first embodiment described above, the exhaust air-fuel ratio is controlled to ABYF1 and ABYF2 in order to form different exhaust flow rate environments. However, the control of the exhaust gas flow rate is not limited to the method using the air-fuel ratio control, and may be controlled to a desired exhaust gas flow rate using another known method. As a result, the present invention can be realized even when there is no fixed correlation between the exhaust air-fuel ratio and the exhaust flow rate.

  Further, according to the first embodiment described above, the control target air-fuel ratio is controlled to ABYF1 and ABYF2 smaller than ABYF1, but by setting ABYF2 to a smaller value, the fuel property determination accuracy is increased. Can be effectively increased. That is, when the control target air-fuel ratio is small, that is, when the exhaust gas flow rate is small, the A / F peak amount due to the rich spike increases. For this reason, if ABYF2 is set to a smaller value, the deviation ΔP of the A / F peak amount becomes a larger value, so that the determination error can be effectively reduced.

  Further, according to the first embodiment described above, the fuel property is determined based on the deviation ΔP of the A / F peak amount, but the parameter that can be used for the determination is not limited to the deviation ΔP. FIG. 7 is a diagram showing an exhaust air-fuel ratio curve when a rich spike is performed. As shown in this figure, based on the peak air-fuel ratios PABYF1 and PABYF2 due to the rich spike, these deviations ΔP ′ may be calculated to determine the fuel property (T90).

  In the first embodiment described above, the diesel engine 10 corresponds to the “internal combustion engine” in the first invention, and the A / F sensor 52 corresponds to the “air-fuel ratio detection means” in the first invention. ing. Further, when the ECU 50 executes the process of step 102 or 108, the “air-fuel ratio control means” and the “exhaust flow rate control means” in the first invention execute the process of step 104 or 110. Thus, the “rich spike means” in the first invention executes the processing of step 116, thereby realizing the “determination means” in the first invention.

  In the first embodiment described above, the ECU 50 executes the processing of step 102 or 108, thereby realizing the “air-fuel ratio control means” and the “exhaust flow rate control means” in the second invention. Has been.

  In the first embodiment described above, the air-fuel ratio ABYF1 is set to the “first air-fuel ratio” in the third invention, the air-fuel ratio ABYF2 is set to the “second air-fuel ratio” in the third invention, and the A / F The peak amount ΔPABYF1 corresponds to the “first air-fuel ratio deviation” in the third invention, and the A / F peak amount ΔPABYF1 corresponds to the “first air-fuel ratio” in the third invention. In addition, when the ECU 50 executes the process of step 106, the “first arithmetic means” in the third invention executes the process of step 112, whereby the “first calculation means” in the third invention is executed. Two calculation means "are realized.

  In the first embodiment described above, the deviation ΔP corresponds to the “deviation” in the fourth aspect of the invention, and the ECU 50 executes the process of step 114, so that “ A “third calculating means” is realized.

  In the first embodiment, the exhaust injector 46 corresponds to the “fuel injection valve” in the eighth aspect of the invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 9 described later using the hardware configuration shown in FIG.

  In the first embodiment described above, rich spikes are performed at different control target air-fuel ratios, and the fuel property (T90) is determined based on the detected deviation ΔP of the A / F peak amount. Here, the fuel property is not limited to the deviation ΔP of the A / F peak amount, but is, for example, the change ratio of the A / F peak amount with respect to the change of the control target air-fuel ratio (hereinafter referred to as “A / F peak slope”). It is also possible to make a determination based on this. FIG. 8 is a diagram showing the relationship between the control target air-fuel ratio and the A / F peak amount in the air-fuel ratio curve shown in FIG. As shown in this figure, the A / F peak slope α1 of the highly evaporative fuel is smaller than the A / F peak slope α2 of the low evaporative fuel. That is, the A / F peak slope varies depending on the fuel properties.

  Therefore, in the second embodiment, rich spikes are performed at different control target air-fuel ratios, and the fuel property (T90) is determined based on the detected A / F peak slope. When calculating the A / F peak slope, there is no restriction on the selection of the control target air-fuel ratio. For this reason, for example, when a fuel with poor ignitability is used, the control target air-fuel ratio can be set within a region where no misfire occurs. As described above, since the selection range of the control target air-fuel ratio at the time of fuel property determination is increased, it is possible to effectively determine the fuel property corresponding to various conditions (fuel type, operating condition, etc.).

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 9, the specific content of the process performed in this Embodiment is demonstrated. FIG. 9 is a flowchart of a routine executed by the ECU 50 to determine the property (T90) of the supplied fuel.

  In the routine shown in FIG. 9, first, the operating condition of the diesel engine 10 is detected (step 200). Next, the exhaust air-fuel ratio is controlled to ABYF1 (step 202). If the exhaust air-fuel ratio is controlled to ABYF1 in step 202, then a rich spike is performed (step 204). Next, an A / F peak amount ΔPABYF1 is acquired (step 206). Next, the exhaust air-fuel ratio is controlled to ABYF2 (step 208). Next, a rich spike is performed (step 210). Next, the A / F peak amount ΔPABYF2 is detected (step 212). Here, specifically, the same processing as in steps 100 to 112 is executed.

In the routine shown in FIG. 9, next, the A / F peak slope α is calculated (step 214). Specifically, ABYF1, ABYF2, and the A / F peak amounts ΔPABYF1 and ΔPABYF2 detected in steps 206 and 212 are substituted into the following equation (3), and the A / F peak slope α is calculated. The
α = (ΔPABYF1-ΔPABYF2) / (ABYF1-ABYF2) (3)

  Next, the fuel property (T90) is determined (step 216). FIG. 10 shows a map defining the relationship between the A / F peak slope α and T90 (° C.). As shown in this map, T90 has a larger value as the A / F peak slope α is larger. The ECU 50 stores a map shown in FIG. Specifically, T90 corresponding to the A / F peak slope α calculated in step 214 is specified according to the map shown in FIG.

  As described above, according to the second embodiment, rich spikes can be performed at different control target air-fuel ratios, and the fuel property (T90) can be determined based on the detected A / F peak slope. . As a result, the influence of the stationary error component superimposed on the sensor output can be eliminated, so that the fuel property (T90) of the fuel supplied to the engine can be accurately determined.

  Further, according to the second embodiment described above, since the fuel property (T90) is determined based on the A / F peak slope, there is no restriction on the selection of the control target air-fuel ratio. For this reason, since the selection range of the control target air-fuel ratio becomes large, it is possible to effectively determine the fuel properties corresponding to various conditions (fuel type, operating conditions, etc.).

  By the way, according to Embodiment 2 mentioned above, although it is supposed that the fuel property of the fuel supplied to the diesel engine 10 is determined, the internal combustion engine to which this invention is applied is not restricted to a diesel engine. That is, a gasoline engine using gasoline as a fuel may be used, or another known internal combustion engine may be used.

  Further, according to the second embodiment described above, T90 is determined as the fuel property, but the fuel property that can be determined is not limited to T90. That is, if the relationship between the A / F peak slope α and other fuel properties (for example, T50) is stored in advance as a map, the same processing as the above processing is executed, so that other fuel properties can be accurately obtained. Can be judged well.

  Further, according to the second embodiment described above, the exhaust air-fuel ratio is controlled to ABYF1 and ABYF2 in order to form different exhaust flow rate environments. However, the control of the exhaust gas flow rate is not limited to the method using the air-fuel ratio control, and may be controlled to a desired exhaust gas flow rate using another known method. As a result, the present invention can be realized even when there is no fixed correlation between the exhaust air-fuel ratio and the exhaust flow rate.

  Further, according to the second embodiment described above, the control target air-fuel ratio is controlled to ABYF1 and ABYF2, but the set control target air-fuel ratio is not limited to this. That is, if the A / F peak slope α can be calculated, the fuel property (T90) can be determined according to the map shown in FIG.

  Further, when setting the control target air-fuel ratio, the accuracy of determining the fuel property can be effectively increased by setting ABYF2 to a smaller value. That is, when the control target air-fuel ratio is small, that is, when the exhaust gas flow rate is small, the A / F peak amount due to the rich spike increases. For this reason, if ABYF2 is set to a smaller value, the A / F peak slope α becomes a larger value, so that the determination error can be effectively reduced.

  Further, according to the second embodiment described above, two different control target air-fuel ratios are set and the A / F peak slope α is calculated. However, the set control target air-fuel ratio is not limited to two. . That is, if the plurality of control target air-fuel ratios are set and the A / F peak slope is calculated, the accuracy of the A / F peak slope α can be effectively increased.

  In the second embodiment described above, the diesel engine 10 corresponds to the “internal combustion engine” in the first invention, and the A / F sensor 52 corresponds to the “air-fuel ratio detection means” in the first invention. ing. Further, when the ECU 50 executes the process of step 202 or 208, the “air-fuel ratio control means” and the “exhaust flow rate control means” in the first invention execute the process of step 204 or 210. Thus, the “rich spike means” in the first invention executes the processing of step 216, thereby realizing the “determination means” in the first invention.

  In the second embodiment described above, the ECU 50 executes the processing of step 202 or 208, whereby the “air-fuel ratio control means” and the “exhaust flow rate control means” in the second invention are realized. Has been.

  In the second embodiment described above, the air-fuel ratio ABYF1 is set to the “first air-fuel ratio” in the third invention, the air-fuel ratio ABYF2 is set to the “second air-fuel ratio” in the third invention, and the A / F The peak amount ΔPABYF1 corresponds to the “first air-fuel ratio deviation” in the third invention, and the A / F peak amount ΔPABYF1 corresponds to the “first air-fuel ratio” in the third invention. In addition, when the ECU 50 executes the process of step 206, the “first arithmetic means” in the third invention executes the process of step 212, whereby the “first arithmetic unit” in the third invention is executed. Two calculation means "are realized.

  In the second embodiment described above, the inclination α corresponds to the “first ratio” in the fifth invention, and the ECU 50 executes the process of step 214, whereby the fifth invention. The “fourth calculation means” in FIG.

  In the second embodiment described above, the exhaust injector 46 corresponds to the “fuel injection valve” in the eighth aspect of the invention.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIGS. In addition to the hardware configuration shown in FIG. 1, the system according to the present embodiment uses means for controlling the temperature of exhaust gas discharged from the diesel engine 10 (hereinafter referred to as “exhaust temperature”). Can be realized. The means for controlling the exhaust temperature can be realized by using known means such as a method for controlling the fuel injection timing and a method for controlling the bypass amount of the intercooler 32.

  In the first embodiment described above, rich spikes are performed at different control target air-fuel ratios, and the fuel property (T90) is determined based on the detected deviation ΔP of the A / F peak amount. Here, under the condition that the A / F peak amount increases to the vicinity of the maximum value (that is, the A / F peak amount when all the fuel is evaporated by the rich spike), the difference in fuel evaporability is A / F. It becomes difficult to appear in the peak amount. For this reason, when the deviation ΔP is detected based on such an A / F peak amount, it is assumed that the determination error becomes large.

  Here, under conditions where the exhaust gas temperature is low, the difference in evaporability due to fuel appears significantly. FIG. 11 is a diagram showing an exhaust air-fuel ratio curve when a rich spike is performed. As shown in this figure, the A / F peak amount ΔPABYF1 ′ when the exhaust gas temperature is controlled to 250 ° C. under the condition where the control target air-fuel ratio is ABYF1 (> ABYF2) is the case where the exhaust gas temperature is 300 ° C. It is smaller than the A / F peak amount ΔPABYF1.

  Therefore, in the third embodiment, the exhaust gas temperature condition is individually set for each control target air-fuel ratio in the fuel property determination in the first embodiment described above. More specifically, the exhaust temperature condition when the control target air-fuel ratio is ABYF1 is controlled to a condition where the exhaust temperature is low (for example, 250 ° C.). As a result, the evaporability of the fuel can be effectively reflected in the deviation ΔP of the A / F peak amount, so that the fuel property determination accuracy can be effectively increased.

  Further, the setting of the exhaust gas temperature condition can be applied to the determination of the fuel property in the second embodiment described above. FIG. 12 is a diagram showing the relationship between the control target air-fuel ratio and the A / F peak amount in the air-fuel ratio curve shown in FIG. As shown in this figure, if the exhaust temperature condition when the control target air-fuel ratio is ABYF1 is set to a condition where the exhaust temperature is low, the A / F peak slope increases. This indicates that the fuel evaporation is more reflected in the A / F peak slope. For this reason, the fuel property can be accurately determined by executing the fuel property determination process according to the second embodiment described above based on the A / F peak slope α ′ when different exhaust temperature conditions are set. it can.

  Further, in the third embodiment, the fuel property can be determined based on the relationship between the exhaust temperature condition and the A / F peak amount. FIG. 13 is a graph showing the relationship between the exhaust gas temperature and the A / F peak amount in the air-fuel ratio curve shown in FIG. As shown in this figure, when the ratio of the change in the A / F peak amount with respect to the change in the exhaust temperature is A / F peak slope β, there is a constant between the A / F peak slope β and the fuel property (T90). Correlation exists. FIG. 14 shows a map defining the relationship between the A / F peak slope β and T90 (° C.). As shown in this map, T90 has a larger value as the A / F peak slope β is larger. Therefore, the fuel property can be accurately determined by executing the fuel property determination process according to the map. Hereinafter, specific processing for determining the fuel property (T90) based on the A / F peak slope β will be described in detail with reference to flowcharts.

[Specific Processing in Embodiment 3]
Next, with reference to FIG. 15, the specific content of the process performed in this Embodiment 3 is demonstrated. FIG. 15 is a flowchart of a routine executed by the ECU 50 to determine the property (T90) of the supplied fuel based on the A / F peak slope β.

  In the routine shown in FIG. 15, first, the operating condition of the diesel engine 10 is detected (step 300). Next, the exhaust air-fuel ratio is controlled to ABYF1 (step 302). Here, specifically, the same processing as in steps 100 to 102 is executed.

  Next, the exhaust temperature is controlled to T1 (250 ° C.) (step 304). As the exhaust temperature T1, a preset temperature is used as a temperature at which a difference in evaporability of fuel supplied to the diesel engine 10 appears remarkably. If the exhaust temperature is controlled to T1 under the condition where the exhaust air-fuel ratio is controlled to ABYF1, then a rich spike is performed (step 306). Next, the A / F peak amount ΔPABYF1 ′ is detected (step 308). Next, the exhaust air-fuel ratio is controlled to ABYF2 (step 310). Here, specifically, the same processing as in steps 104 to 108 is executed.

  Next, the exhaust temperature is controlled to T2 (300 ° C.) (step 312). As the exhaust temperature T2, a temperature set in advance as a temperature higher than T1 is used. Next, a rich spike is performed (step 314). Next, the A / F peak amount ΔPABYF2 is detected (step 316). Here, specifically, the same processing as in steps 110 to 112 is executed.

In the routine shown in FIG. 15, the A / F peak slope β is then calculated (step 318). Specifically, the A / F peak amounts ΔPABYF1 ′ and ΔPABYF2 detected in steps 308 and 316 are substituted into the following equation (4), and the A / F peak slope β is calculated.
β = (ΔPABYF2−ΔPABYF1 ′) / (T2−T1) (4)

  Next, the fuel property (T90) is determined (step 320). The ECU 50 stores the map shown in FIG. 14 described above. Specifically, T90 corresponding to the A / F peak slope β calculated in step 318 is specified according to the map shown in FIG.

  As described above, according to the third embodiment, by separately setting the exhaust gas temperature conditions at different control target air-fuel ratios, it is possible to effectively reflect the fuel evaporation in the A / F peak slope β. it can. For this reason, the precision which determines the fuel property (T90) of the fuel supplied to an engine can further be improved.

  By the way, according to Embodiment 3 mentioned above, it is supposed that the fuel property of the fuel supplied to the diesel engine 10 is determined, but the internal combustion engine to which the present invention is applied is not limited to the diesel engine. That is, a gasoline engine using gasoline as a fuel may be used, or another known internal combustion engine may be used.

  Further, according to the third embodiment described above, T90 is determined as the fuel property, but the fuel property that can be determined is not limited to T90. That is, if the relationship between the A / F peak slope β and other fuel properties (for example, T50) is stored in advance as a map, the same processing as the above processing is executed, so that other fuel properties can be accurately obtained. Can be judged well.

  Further, according to the third embodiment described above, the exhaust air-fuel ratio is controlled to ABYF1 and ABYF2 in order to form different exhaust flow rate environments. However, the control of the exhaust flow rate is not limited to the method using the air-fuel ratio control, and may be controlled to a desired exhaust flow rate using another known method. As a result, the present invention can be realized even when there is no fixed correlation between the exhaust air-fuel ratio and the exhaust flow rate.

  Further, according to Embodiment 3 described above, the control target air-fuel ratio is controlled to ABYF1 and ABYF2, but the set control target air-fuel ratio is not limited to this. Also, regarding the exhaust temperatures T1 and T2, appropriate values can be set according to the fuel properties to be determined.

  Further, when setting the control target air-fuel ratio, the accuracy of determining the fuel property can be effectively increased by setting ABYF2 to a smaller value. That is, when the control target air-fuel ratio is small, that is, when the exhaust gas flow rate is small, the rich spike A / F peak amount increases. For this reason, if ABYF2 is set to a smaller value, the A / F peak slope β becomes a larger value, so that the determination error can be effectively reduced.

  In the third embodiment described above, the diesel engine 10 corresponds to the “internal combustion engine” in the first invention, and the A / F sensor 52 corresponds to the “air-fuel ratio detecting means” in the first invention. ing. Further, when the ECU 50 executes the process of step 302 or 310, the “air-fuel ratio control means” and the “exhaust flow rate control means” in the first invention execute the process of step 306 or 314. Thus, the “rich spike means” in the first invention executes the processing of step 320, thereby realizing the “determination means” in the first invention.

  In the third embodiment described above, the ECU 50 executes the processing of step 302 or 310, thereby realizing the “air-fuel ratio control means” and the “exhaust flow rate control means” in the second invention. Has been.

  In Embodiment 3 described above, the air / fuel ratio ABYF1 is set to the “first air / fuel ratio” in the third invention, the air / fuel ratio ABYF2 is set to the “second air / fuel ratio” in the third invention, and the A / F The peak amount ΔPABYF1 corresponds to the “first air-fuel ratio deviation” in the third invention, and the A / F peak amount ΔPABYF1 corresponds to the “first air-fuel ratio” in the third invention. Further, when the ECU 50 executes the process of step 308, the “first arithmetic means” in the third invention executes the process of step 316, whereby the “first arithmetic means” in the third invention is executed. Two calculation means "are realized.

  In the third embodiment described above, the “temperature control means” according to the sixth aspect of the present invention is implemented when the ECU 50 executes the process of step 304 or 312.

  In the third embodiment described above, the slope β corresponds to the “second ratio” in the seventh invention, and the ECU 50 executes the process of step 318, whereby the seventh invention. The “fifth computing means” in FIG.

  In the third embodiment described above, the exhaust injector 46 corresponds to the “fuel injection valve” according to the eighth aspect of the present invention.

It is a figure for demonstrating schematic structure of the internal combustion engine system as Embodiment 1 of this invention. It is a figure which shows the change of A / F sensor output when a rich spike is performed. It is a figure which shows the exhaust air fuel ratio curve at the time of implementing a rich spike. It is a figure which shows the relationship between deviation (DELTA) P of the A / F peak amount at the time of the rich spike in a different control target air fuel ratio, and fuel property (T90). It is a flowchart of the routine performed in Embodiment 1 of the present invention. The map which prescribed | regulated the relationship between deviation (DELTA) P and a fuel property (T90) is shown. It is a figure which shows the exhaust air fuel ratio curve at the time of implementing a rich spike. FIG. 4 is a diagram showing a relationship between a control target air-fuel ratio and an A / F peak amount in the air-fuel ratio curve shown in FIG. 3. It is a flowchart of the routine performed in Embodiment 2 of this invention. The map which prescribed | regulated the relationship between A / F peak inclination (alpha) and a fuel property (T90) is shown. It is a figure which shows the exhaust air fuel ratio curve at the time of implementing a rich spike. It is a figure which shows the relationship between a control target air fuel ratio and A / F peak amount in the air fuel ratio curve shown in FIG. It is a figure which shows the relationship between exhaust temperature and A / F peak amount in the air fuel ratio curve shown in FIG. The map which prescribed | regulated the relationship between A / F peak inclination (beta) and a fuel property (T90) is shown. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 16 Supply pump 18 Exhaust passage 20 Exhaust manifold 24 Turbocharger 26 Aftertreatment device 28 Intake passage 30 Air cleaner 32 Intercooler 34 Intake manifold 36 Inlet throttle valve 40 EGR passage 42 EGR cooler 44 EGR valve 46 Exhaust injector 50 ECU (Electronic Control Unit)
52 A / F sensor

Claims (8)

Air-fuel ratio control means for controlling the air-fuel ratio of the exhaust gas of the internal combustion engine to a control target air-fuel ratio;
An air-fuel ratio detecting means provided in an exhaust passage of the internal combustion engine for detecting the air-fuel ratio;
Exhaust flow rate control means for controlling the flow rate of exhaust gas (hereinafter referred to as exhaust flow rate);
Rich spike means for temporarily changing the air-fuel ratio to a richer side than the control target air-fuel ratio;
Change of the air-fuel ratio when the rich spike means is executed under a situation where the exhaust flow rate is a predetermined exhaust flow rate, and the rich spike means is executed under a situation where the exhaust flow rate is different from the predetermined exhaust flow rate Determination means for determining a fuel property of the fuel supplied to the internal combustion engine based on the change in the air-fuel ratio in the case;
A fuel property determination apparatus for an internal combustion engine, comprising:   2. The fuel for an internal combustion engine according to claim 1, wherein the air-fuel ratio control means controls the air-fuel ratio to the control target air-fuel ratio by changing the exhaust flow rate using the exhaust flow rate control means. Property determination device. The determination means includes
A deviation between the peak of the air-fuel ratio and the first air-fuel ratio (hereinafter referred to as a first air-fuel ratio deviation) when the rich spike means is executed in a situation where the control target air-fuel ratio is a predetermined first air-fuel ratio. First computing means for computing
Deviation between the peak of the air-fuel ratio and the second air-fuel ratio when the rich spike means is executed under the condition that the control target air-fuel ratio is a predetermined second air-fuel ratio richer than the first air-fuel ratio. (Hereinafter, the second air-fuel ratio deviation) is calculated, and
The fuel property determination device for an internal combustion engine according to claim 2, wherein the fuel property of the fuel of the internal combustion engine is determined based on the first air-fuel ratio deviation and the second air-fuel ratio deviation.   The determination means includes third calculation means for calculating a deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation, and determines the fuel property based on a comparison between the deviation and a predetermined value. The fuel property determination apparatus for an internal combustion engine according to claim 3.   The determination means calculates a ratio (hereinafter referred to as a first ratio) of a deviation between the first air-fuel ratio deviation and the second air-fuel ratio deviation with respect to a deviation between the first air-fuel ratio and the second air-fuel ratio. 4. The fuel property determination device for an internal combustion engine according to claim 3, wherein the fuel property is determined based on a comparison between the first ratio and a predetermined value. A temperature control means for controlling the temperature of the exhaust gas;
6. The exhaust gas temperature when the control target air-fuel ratio is the first air-fuel ratio is controlled to be lower than that when the control target air-fuel ratio is the second air-fuel ratio. 2. A fuel property determination device for an internal combustion engine according to item 1.   The determination means includes the first air-fuel ratio deviation with respect to the deviation between the temperature of the exhaust gas when the control target air-fuel ratio is the first air-fuel ratio and the temperature of the exhaust gas when the control target air-fuel ratio is the second air-fuel ratio. Including a fifth calculating means for calculating a ratio of the deviation from the second air-fuel ratio deviation (hereinafter referred to as a second ratio), and determining the fuel property based on a comparison between the second ratio and a predetermined value. The fuel property determination device for an internal combustion engine according to claim 6.   The rich spike means includes a fuel injection valve provided in the exhaust passage on the upstream side of the air-fuel ratio detection means, and injects a predetermined amount of fuel into the exhaust passage from the fuel injection valve. 8. The fuel property determination apparatus for an internal combustion engine according to claim 1,

Images