JP2018031341A - Fuel property determination device and combustion control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the high-level satisfaction of both accurately determining fuel property and securing the opportunities of determining the fuel property as many as possible.SOLUTION: A fuel property determination device retards a fuel injection timing and determines fuel property (for example, a cetane value) on the basis of a combustion fluctuation of an engine at this time. On the basis of either the combustion fluctuation right after starting retarding the fuel injection timing or the average of the combustion fluctuations when performing the retard of the fuel injection timing over a predetermined period, the fuel property is determined. On the basis of the determination result, a combustion control amount such as the fuel injection timing at the time of normal operation is decided.SELECTED DRAWING: Figure 3

Description

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

  In the engine, the fuel property greatly affects the combustion property (for example, the ignition property) of the engine, but the fuel property may vary greatly depending on the region. For this reason, when the combustion control amount of the engine is set to the same value, when the fuel property is changed, the combustibility is greatly different. Patent Document 1 discloses a method in which the fuel injection timing is retarded and the cetane number as a fuel property is detected based on the combustion state (misfire or ignition) at that time.

JP 2009-36027 A

  In order to accurately determine the fuel properties, it is preferable to perform retarding of the fuel injection timing over a predetermined period and to determine the fuel properties based on the average (average value) of combustion fluctuations during the predetermined period. . However, since the fuel injection timing may not be retarded over a predetermined period, it is not desirable from the viewpoint of securing as many opportunities as possible to determine the fuel properties.

  The present invention has been made in view of the circumstances as described above, and the first object thereof is to both accurately determine the fuel properties and to ensure as many fuel property determination opportunities as possible. It is an object of the present invention to provide an engine fuel property determination device that can be satisfied at a high level.

  A second object of the present invention is to provide an engine combustion control device that can appropriately perform engine combustion control in accordance with the difference in fuel properties.

In order to achieve the first object, the following first solution is adopted in the present invention. That is, as described in claim 1,
The fuel injection timing is retarded, and the fuel property is determined based on the combustion fluctuation of the engine at that time,
First detection means for detecting combustion fluctuations immediately after the start of retarding the fuel injection timing;
Second detection means for detecting an average of combustion fluctuations when retarding the fuel injection timing over a predetermined period;
First determination means for determining fuel properties based on any of the combustion fluctuations detected by each of the detection means;
It is supposed to be equipped with.

  According to the above-described solution method, it is possible to perform accurate determination based on the average of combustion fluctuations and determination based on combustion fluctuations immediately after the start of retarding, which can ensure a large number of determination opportunities, as determination of fuel properties. As a result, it is possible to satisfy both of the determination accuracy and the determination opportunity at a high level.

In order to achieve the first object, the following second solution is adopted in the present invention. That is, as described in claim 2,
The fuel injection timing is retarded, and the fuel property is determined based on the combustion fluctuation of the engine at that time,
A first detecting means for detecting a combustion fluctuation immediately after the start of the retard at the fuel injection timing in a state where the retard amount at the fuel injection timing is set to the first set amount;
Second detection means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the first set amount;
First determination means for determining a fuel property based on any of the combustion fluctuations detected by the first detection means and the second detection means;
Third detection means for detecting a combustion fluctuation immediately after the start of the retard of the fuel injection timing in a state where the retard amount of the fuel injection timing is set to a second set amount larger than the first set amount;
Fourth detecting means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the second set amount;
Second determination means for determining a fuel property based on any of the combustion fluctuations detected by the third detection means and the fourth detection means;
With
On the condition that the fuel property determined by the first determining means is good enough to be a predetermined value or more, the fuel injection timing is retarded at the second set amount, and the determination by the second determining means is performed. Called
It is like that.

  According to the above solution, the effect corresponding to claim 1 can be obtained. Also, initially, by setting the retard amount to a small first set amount, when the fuel property currently in use is poor, a situation of misfire or engine stop may occur due to the retard of the fuel injection timing. Can be prevented. Furthermore, when it is confirmed that the fuel property is good to a certain degree, the retard amount at the fuel injection timing is set to a large second set amount, and the fuel property for the fuel having a good fuel property to a certain degree is determined. Can do.

A preferred mode based on the first solution technique or the second solution technique is as described in claims 3 to 6. That is,
When the retard is performed over the predetermined period, the first determination unit determines the fuel property based on the average of the combustion fluctuations detected by the second detection unit, while over the predetermined period. When all the retards are not performed, the fuel property is determined based on the combustion fluctuation detected by the first detection means (corresponding to claim 3). In this case, it is preferable to determine the fuel property with emphasis on ensuring the determination accuracy.

  When the retard is performed over the predetermined period, the second determination unit determines the fuel property based on the average of the combustion fluctuations detected by the fourth detection unit, while over the predetermined period. When all the retards are not performed, the fuel property is determined based on the combustion fluctuation detected by the third detecting means (corresponding to claim 4). In this case, it is preferable to determine the fuel property with emphasis on ensuring the determination accuracy.

  The combustion fluctuations are assumed to be engine speed fluctuations (corresponding to claim 5). In this case, the fuel property can be determined by accurately reflecting the combustion fluctuation and using the engine speed that is easy to detect.

  The fuel property to be determined is the cetane number (corresponding to claim 6). In this case, the cetane number that greatly affects the ignitability can be determined.

In order to achieve the second object, the following third solution is adopted in the present invention. That is, as described in claim 7,
When a predetermined operating condition is satisfied, the fuel injection timing is retarded, and the engine combustion control amount in the normal operating state is determined based on the combustion fluctuation of the engine at that time,
First detection means for detecting combustion fluctuations immediately after the start of retarding the fuel injection timing;
Second detection means for detecting an average of combustion fluctuations when retarding the fuel injection timing over a predetermined period;
First control amount determining means for determining a combustion control amount of the engine in a normal operating state based on any of the combustion fluctuations detected by each of the detecting means;
It is supposed to be equipped with. According to the above solution, it is possible to appropriately determine the combustion control amount in accordance with the fuel property while obtaining the effect corresponding to the first aspect.

In order to achieve the second object, the following fourth solution is adopted in the present invention. That is, as described in claim 8,
When a predetermined operating condition is satisfied, the fuel injection timing is retarded, and the engine combustion control amount in the normal operating state is determined based on the combustion fluctuation of the engine at that time,
A first detecting means for detecting a combustion fluctuation immediately after the start of the retard at the fuel injection timing in a state where the retard amount at the fuel injection timing is set to the first set amount;
Second detection means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the first set amount;
First control amount determining means for determining a combustion control amount of the engine in a normal operation state based on any of the combustion fluctuations detected by the first detecting means and the second detecting means;
Third detection means for detecting a combustion fluctuation immediately after the start of the retard of the fuel injection timing in a state where the retard amount of the fuel injection timing is set to a second set amount larger than the first set amount;
Fourth detecting means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the second set amount;
Second control amount determining means for determining a combustion control amount of the engine in a normal operating state based on any of the combustion fluctuations detected by the third detecting means and the fourth detecting means;
With
On the condition that the combustion control amount determined by the first control amount determination means does not correspond to a bad combustion state, the fuel injection timing is retarded at the second set amount, and the first (2) The combustion control amount is determined by the control amount determination means.
It is like that. According to the above-described solution technique, it is possible to appropriately determine the combustion control amount according to the fuel property while obtaining the effect corresponding to the second aspect.

A preferred mode based on the third solution technique and the fourth solution technique is as set forth in claim 9. That is,
The predetermined operating condition is set to an idling operation of the engine (corresponding to claim 9). In this case, it is preferable in securing a sufficient opportunity to set the combustion control amount. Moreover, since it is based on the combustion fluctuation at the time of idling operation in which the engine speed is substantially constant, it is preferable for more appropriately setting the combustion control amount.

  According to the present invention, it is possible to satisfy both high-precision determination of fuel properties and ensuring as many opportunities for determination of fuel properties as possible, and appropriate combustion according to fuel properties. Control amount can be set.

The figure which shows an example of the engine to which this invention was applied. The time chart which shows the relationship between the situation which retards fuel-injection time, and engine rotation fluctuation | variation. The flowchart which shows the example of control of this invention.

  In FIG. 1, reference numeral 1 denotes an engine (engine body), which is an in-line four-cylinder automobile diesel engine in the embodiment. The engine 1 has a cylinder 2, a cylinder head 3, and a piston 4 as is known. An intake port 6 and an exhaust port 7 are opened with respect to the combustion chamber 5 formed above the piston 4. The intake port 6 is opened and closed by an intake valve 8, and the exhaust port 7 is opened and closed by an exhaust valve 9. A fuel injection valve 10 is attached to the cylinder head 3 so as to face the combustion chamber 5. In the embodiment, the fuel injection is of a common rail type, and extremely high pressure fuel is injected from the fuel injection valve 10.

  In the intake passage 20 connected to the intake port 6, the air cleaner 21, the compressor wheel 22 a of the first exhaust turbocharger 22, and the compressor of the second exhaust turbocharger 23 are sequentially arranged from the upstream side to the downstream side. A wheel 23a, an intercooler 24, a throttle valve 25, and a surge tank 26 are provided. The surge tank 26 and each cylinder (the intake port 6 thereof) are independently connected by a branched intake passage 27.

  A bypass passage 28 is provided in the intake passage 20. The bypass passage 28 has an upstream end opened to the intake passage 20 between the compressor wheels 22a and 23a. Further, the downstream end of the bypass passage 28 is opened to the intake passage 20 between the compressor wheel 23 a and the intercooler 24. A control valve 29 is disposed in the bypass passage 28.

  In the exhaust passage 30 connected to the exhaust port 7, the turbine wheel 23 b of the second exhaust turbocharger 23, the turbine wheel 22 b of the first exhaust turbocharger 22, sequentially from the upstream side to the downstream side thereof, An oxidation catalyst / NOx catalyst 31, a DPF 32, a urea catalyst 33, and an ammonia processor 34 are connected.

  The exhaust passage 30 has a bypass passage 33 and a wastegate passage 34. The upstream end of the bypass passage 33 is opened to the exhaust passage 30 on the upstream side of the turbine wheel 23b. The downstream end of the bypass passage 33 is opened to the exhaust passage 30 between the turbine wheels 22b and 23b. A control valve 35 for controlling the exhaust gas flow rate is disposed in the bypass passage 33.

  The upstream end of the wastegate passage 34 is opened in the exhaust passage 30 between the turbine wheels 22b and 23b. The downstream end of the waste gate passage 34 is opened to the exhaust passage 30 between the turbine wheel 22 b and the catalyst 31. The wastegate passage 34 is provided with a wastegate valve 36 for exhaust flow control.

  The intake passage 20 and the exhaust passage 30 are connected via an EGR passage 50. The upstream end of the EGR passage 50 is opened to the exhaust passage 30 upstream of the turbine wheel 23b. Further, the downstream end of the EGR passage 50 is opened to the intake passage 20 between the throttle valve 25 and the surge tank 26.

  An EGR cooler 51 is connected to the EGR passage 50, and an EGR valve 52 is disposed on the downstream side of the EGR cooler 51. The EGR passage 50 is provided with a bypass passage 53 that bypasses the EGR cooler 51. The bypass passage 53 has an upstream end opened to the EGR passage 50 upstream of the EGR cooler 51, and a downstream end opened to the EGR passage 50 downstream of the EGR valve 52. A control valve 54 is disposed in the bypass passage 54.

  The first exhaust turbo-type supercharger 22 is large, and the second exhaust turbo-type supercharger 23 is small. In the low rotation and low load range, supercharging is performed mainly by the small second exhaust turbocharger 23, and at this time, the control valves 29 and 35 are closed. In the high load range, supercharging is performed mainly by the large exhaust turbocharger 22, and at this time, the control valves 29 and 35 are opened. When the supercharging pressure exceeds a predetermined upper limit pressure, the waste gate valve 36 is opened.

  Next, a method for determining the fuel property by retarding the fuel injection timing and a method for determining the combustion control amount associated therewith will be described with reference to FIG. First, the retard of the fuel injection amount includes an initial period in which a small retard amount (first set amount) is performed for a predetermined period, and a late period in which a large retard amount (second set amount is greater than the first set amount) for a predetermined period. And divided. In FIG. 2, the period from time t1 to time t2 is the initial period, and the period from time t2 to time t3 is the late period. When the latter period has elapsed, the retard amount at the fuel injection timing is gradually decreased, and the retard amount is set to 0 at time t4 (return to normal operation). In the embodiment, the lengths of the initial period and the latter period are the same, but may be different from each other (particularly, the latter period is made longer than the initial period).

  The detection content of the combustion fluctuation due to the retarded amount of fuel injection is engine rotation fluctuation. Two types of rotational fluctuations are set, and the amount of decrease in engine speed (instantaneous fluctuation amount) immediately after the start of retard and the average (average) of engine speed angular velocity fluctuations for all cylinders during a predetermined period of retarding. The long-term fluctuation amount).

  In the initial period when the retard amount is small (first set amount), a first predetermined value is set for the amount of decrease in engine speed as a determination threshold value for fuel property determination, and the average of angular velocity fluctuations is set. A second predetermined value is set.

  In the latter period of the large retard amount (second set amount), a third predetermined value larger than the first predetermined value is set as the determination threshold value for determining the fuel property, with respect to the amount of decrease in engine speed. A fourth predetermined value larger than the second predetermined value is set for the average angular velocity fluctuation.

  In the initial period, when the average of the angular speed fluctuations of the engine rotation is equal to or higher than the second predetermined value, or when the decrease amount of the engine speed is equal to or higher than the first predetermined value when the initial period cannot be secured, the fuel It is determined that the properties are poor (for example, corresponding to a cetane number of less than 44 CN). In this case, the fuel injection timing that is the combustion control amount is set to the most advanced one.

  The determination of the fuel property in the latter period is executed on the condition that it was not determined that the fuel property based on the average of the angular velocity fluctuation was bad in the initial period. In this later stage determination, when the average of the angular speed fluctuations of the engine rotation is equal to or greater than the fourth predetermined value, or when the amount of decrease in the engine speed is equal to or greater than the third predetermined value when the latter period cannot be secured, It is determined that the property is moderate (for example, the cetane number corresponds to between 44 CN and 48 CN). In this case, the fuel injection timing, which is the combustion control amount, is set to a medium advanced angle.

  In the latter period, the fuel property is good when the amount of decrease in the engine speed is less than the third predetermined value, or when the average angular speed fluctuation of the engine rotation is less than the fourth predetermined value when the latter period cannot be secured ( For example, it is determined that the cetane number is 48 CN or more. In this case, the fuel injection timing as the combustion control amount is set to the most retarded one.

  Note that the retard amount of the fuel injection timing is reduced in the initial period in consideration of the possibility of causing a problem of misfire or engine stop when the currently used fuel property is poor. In the latter period, it is confirmed that the fuel properties are good to some extent, so that the retard amount is increased to improve detection accuracy.

  Next, a control example of the present invention will be described with reference to the flowchart of FIG. In the following description, Q indicates a step. The control content shown in FIG. 3 is the control content in the engine control controller (control unit) U shown in FIG. The input / output relationship for various sensors and devices with respect to the controller U will be described when the flowchart is described. Further, the amount of decrease in engine speed and the amount of change in angular velocity when the fuel injection timing is retarded are calculated (detected) in a separate routine.

  First, in Q1, it is determined whether or not a basic determination condition is satisfied. This determination eliminates environmental conditions severe to combustion. For example, it is determined whether or not the coolant temperature, the intake air temperature, the atmospheric pressure, and the atmospheric temperature input from various sensors to the controller U are within a predetermined range. Become. If the determination in Q1 is NO, it is determined that the environment is inappropriate for determination of fuel properties, and the process returns to Q1.

  If the determination in Q1 is YES, it is determined in Q2 whether or not the engine is idling (for example, whether or not the engine is idling based on the engine speed and the vehicle speed input to the controller U). Determination). If the determination in Q2 is NO, the process returns to Q1. If the determination in Q2 is YES, it is determined in Q3 whether or not combustion is stable. In the embodiment, the determination of Q3 is a determination as to whether or not the fluctuation amount of the engine speed during idling is within a predetermined range (for example, 4 rpm or less).

  If the determination in Q3 is YES, in Q4, the retard of the fuel injection timing is started (the retard amount is a first set amount that is small) in order to perform the fuel property determination in the initial period. Thereafter, in Q5, it is determined whether or not an initial period is secured. If the determination in Q5 is YES, it is determined in Q6 whether or not the average angular velocity fluctuation amount is equal to or greater than a second predetermined value. If YES in Q7, it is determined in Q7 that the fuel property is poor, and the fuel injection timing during normal operation is determined (set) so as to be the most advanced.

  If the determination in Q5 is NO, that is, if the initial period is not secured, it is determined in Q8 whether or not the amount of decrease in engine speed is equal to or greater than a first predetermined value. If YES in Q8, the process proceeds to Q7 described above. If NO in Q8, the process returns to Q1 because the fuel property cannot be determined.

  When the determination at Q6 is NO, the routine proceeds to Q9, where retarding of the fuel injection timing is started in order to determine the fuel property in the later period (the retard amount is a large second set amount).

  After Q9, at Q10, it is determined whether or not the latter period is secured. If the determination in Q10 is YES, it is determined in Q11 whether or not the average angular velocity fluctuation amount is equal to or greater than a fourth predetermined value. If YES in Q11, the fuel property is determined to be medium in Q12, and the fuel injection timing during normal operation is determined (set) to be advanced to a medium level. The If NO in Q11, it is determined in Q13 that the fuel properties are good, and the fuel injection timing during normal operation is determined (set) so that it is most retarded.

  If the determination in Q10 is NO, it is determined in Q14 whether or not the amount of decrease in engine speed is greater than or equal to a third predetermined value. If the determination in Q14 is YES, the process proceeds to Q12. If NO in Q14, the process proceeds to Q13.

  Although the embodiment has been described above, the present invention is not limited to the embodiment, and can be appropriately changed within the scope described in the scope of claims. For example, the invention includes the following cases. . The number of cylinders of the engine 1 is not limited, for example, six cylinders. The combustion control amount that is changed according to the fuel property is not limited to the fuel injection timing, and an appropriate parameter related to the combustion property such as the EGR amount can be selected as appropriate. The combustion fluctuation when the fuel injection timing is retarded is not limited to the reduction amount of the engine speed or the angular velocity fluctuation amount, but an appropriate parameter such as the engine combustion pressure, combustion temperature, exhaust temperature, exhaust pressure, etc. is selected. be able to. The present invention can be applied not only to a diesel engine but also to a gasoline engine. In this case, the fuel property can be, for example, an octane number, and the combustion control amount can be, for example, an ignition timing. Each step or step group shown in the flowchart indicates the function of the controller U, and the name indicating the function can be attached to the name of the means so as to be grasped as a constituent requirement of the controller U.

  The present invention is suitable for application to, for example, an automobile diesel engine.

U: Controller 1: Engine 2: Cylinder
10: Fuel injection valve 20: Intake passage 22: First exhaust turbocharger 23: Second exhaust turbocharger 30: Exhaust passage 50: EGR passage 51: EGR cooler 52: EGR valve

Claims (9)

The fuel injection timing is retarded, and the fuel property is determined based on the combustion fluctuation of the engine at that time,
First detection means for detecting combustion fluctuations immediately after the start of retarding the fuel injection timing;
Second detection means for detecting an average of combustion fluctuations when retarding the fuel injection timing over a predetermined period;
First determination means for determining fuel properties based on any of the combustion fluctuations detected by each of the detection means;
An engine fuel property judging device comprising: The fuel injection timing is retarded, and the fuel property is determined based on the combustion fluctuation of the engine at that time,
A first detecting means for detecting a combustion fluctuation immediately after the start of the retard at the fuel injection timing in a state where the retard amount at the fuel injection timing is set to the first set amount;
Second detection means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the first set amount;
First determination means for determining a fuel property based on any of the combustion fluctuations detected by the first detection means and the second detection means;
Third detection means for detecting a combustion fluctuation immediately after the start of the retard of the fuel injection timing in a state where the retard amount of the fuel injection timing is set to a second set amount larger than the first set amount;
Fourth detecting means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the second set amount;
Second determination means for determining a fuel property based on any of the combustion fluctuations detected by the third detection means and the fourth detection means;
With
On the condition that the fuel property determined by the first determining means is good enough to be a predetermined value or more, the fuel injection timing is retarded at the second set amount, and the determination by the second determining means is performed. Called
An engine fuel property determination device characterized by the above. In claim 1,
When the retard is performed over the predetermined period, the first determination unit determines the fuel property based on the average of the combustion fluctuations detected by the second detection unit, while over the predetermined period. An engine fuel property determination device characterized by determining a fuel property based on a combustion fluctuation detected by the first detection means when no retarding is performed. In claim 2,
When the retard is performed over the predetermined period, the second determination unit determines the fuel property based on the average of the combustion fluctuations detected by the fourth detection unit, while over the predetermined period. An engine fuel property determination device characterized in that when all the retards are not performed, the fuel property is determined based on the combustion fluctuation detected by the third detection means. In any one of Claims 1 thru | or 4,
An engine fuel property determination device, wherein the combustion fluctuation is an engine speed fluctuation. In any one of Claims 1 thru | or 5,
An engine fuel property determining apparatus, wherein the determined fuel property is a cetane number. When a predetermined operating condition is satisfied, the fuel injection timing is retarded, and the engine combustion control amount in the normal operating state is determined based on the combustion fluctuation of the engine at that time,
First detection means for detecting combustion fluctuations immediately after the start of retarding the fuel injection timing;
Second detection means for detecting an average of combustion fluctuations when retarding the fuel injection timing over a predetermined period;
First control amount determining means for determining a combustion control amount of the engine in a normal operating state based on any of the combustion fluctuations detected by each of the detecting means;
An engine combustion control device comprising: When a predetermined operating condition is satisfied, the fuel injection timing is retarded, and the engine combustion control amount in the normal operating state is determined based on the combustion fluctuation of the engine at that time,
A first detecting means for detecting a combustion fluctuation immediately after the start of the retard at the fuel injection timing in a state where the retard amount at the fuel injection timing is set to the first set amount;
Second detection means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the first set amount;
First control amount determining means for determining a combustion control amount of the engine in a normal operation state based on any of the combustion fluctuations detected by the first detecting means and the second detecting means;
Third detection means for detecting a combustion fluctuation immediately after the start of the retard of the fuel injection timing in a state where the retard amount of the fuel injection timing is set to a second set amount larger than the first set amount;
Fourth detecting means for detecting an average of combustion fluctuations when the fuel injection timing is retarded over a predetermined period in a state where the retard amount of the fuel injection timing is the second set amount;
Second control amount determining means for determining a combustion control amount of the engine in a normal operating state based on any of the combustion fluctuations detected by the third detecting means and the fourth detecting means;
With
On the condition that the combustion control amount determined by the first control amount determination means does not correspond to a bad combustion state, the fuel injection timing is retarded at the second set amount, and the first (2) The combustion control amount is determined by the control amount determination means.
An engine combustion control device. In claim 7 or claim 8,
The engine combustion control apparatus according to claim 1, wherein the predetermined operating condition is an idling operation of the engine.

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