KR101568643B1 - Control device for internal combustion engine - Google Patents

Abstract

The control device 100 of the internal combustion engine is provided with an ignition energy calculation section for calculating ignition energy which is energy required for ignition of fuel in the cylinder 11 of the internal combustion engine 5 based on the cetane number of the fuel, An ignition delay time calculating unit that calculates an ignition delay time which is a time required until the accumulated value of the in-cylinder energy becomes equal to or higher than the ignition energy after the fuel is injected into the cylinder, And a time calculating unit.

Description

[0001] CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE [0002]

The present invention relates to a control apparatus for an internal combustion engine.

BACKGROUND ART Conventionally, a technique has been known that calculates the ignition delay time which is the time from the injection of fuel from the fuel injection valve to the ignition of the fuel. For example, Patent Document 1 discloses a technique for calculating the ignition delay time when fuel is injected at the base fuel injection timing based on the cylinder inner temperature and the cylinder inner pressure at the base fuel injection timing.

Japanese Patent Application Laid-Open No. 2008-101591

However, in the technology related to Patent Document 1, since the cetane number is not used as the parameter used for calculating the ignition delay time, the ignition delay time according to the cetane number must be precisely set to a high accuracy I could not say that I could calculate the road.

An object of the present invention is to provide a control apparatus for an internal combustion engine capable of accurately calculating ignition delay time according to cetane number.

The control apparatus for an internal combustion engine according to the present invention includes an ignition energy calculating section for calculating an ignition energy which is energy required for ignition of fuel in a cylinder of an internal combustion engine based on the cetane number of fuel, And an ignition delay time calculating unit that calculates an ignition delay time for calculating a time required until the integrated value of the in-cylinder energy becomes equal to or higher than the ignition energy after the fuel is injected into the cylinder, And a calculating unit.

According to the control apparatus for an internal combustion engine according to the present invention, the time required until the integrated value of the in-cylinder energy becomes equal to or higher than the ignition energy calculated based on the cetane number after the fuel is injected into the cylinder is calculated as the ignition delay time . Thereby, the ignition delay time according to the cetane number can be calculated with high accuracy.

The configuration may include a control unit for controlling the fuel injection timing based on the ignition delay time calculated by the ignition delay time calculating unit.

According to this configuration, the fuel injection timing can be controlled based on the ignition delay time corresponding to the cetane number. Thereby, even when cetane fuel different from the cetane number originally assumed as the fuel of the internal combustion engine is used, deterioration of the combustion state such as fuel consumption and emission can be suppressed.

According to the present invention, it is possible to provide a control apparatus for an internal combustion engine capable of accurately calculating ignition delay time according to cetane number.

1 is a schematic view showing an example of an internal combustion engine to which a control device is applied.
2 is a diagram showing an example of a flow chart when the control apparatus executes ignition delay time calculation control.
Fig. 3 (a) is a schematic diagram showing an example of a map defined by associating the ignition energy with the cetane number.
FIG. 3 (b) is a schematic diagram for visually explaining a calculation method of the ignition delay time.

Hereinafter, embodiments for carrying out the present invention will be described.

<Examples>

A control apparatus for an internal combustion engine (hereinafter referred to as control apparatus 100) according to an embodiment of the present invention will be described. First, an example of the configuration of the internal combustion engine to which the control device 100 is applied will be described, and then the details of the control device 100 will be described. 1 is a schematic diagram showing an example of an internal combustion engine 5 to which a control device 100 is applied. The internal combustion engine 5 shown in Fig. 1 is mounted on a vehicle. In this embodiment, as an example of the internal combustion engine 5, a compression ignition type internal combustion engine, specifically, a diesel engine is used. The internal combustion engine 5 includes an engine main body 10, an intake passage 20, an exhaust passage 21, a throttle 22, a fuel injection valve 30, a common rail 40, 41, an exhaust gas recirculation (EGR) passage 50, an EGR valve 51, a turbocharger 60, an intercooler 70, an air flow sensor 80, a temperature sensor 81, An internal pressure sensor 82, a fuel property sensor 83, and a control device 100. [

The engine main body 10 has a cylinder block in which a cylinder 11 is formed, a cylinder head disposed in an upper portion of the cylinder block, and a piston arranged in the cylinder 11. In the present embodiment, the number of the cylinders 11 is plural (specifically, four). The downstream side of the intake passage 20 is branched and connected to the respective cylinders 11. Fresh air flows in from the end on the upstream side of the intake passage (20). The exhaust passage 21 is branched on the upstream side and connected to the respective cylinders 11. The throttle (22) is disposed in the intake passage (20). The throttle 22 adjusts the amount of air introduced into the cylinder 11 by opening and closing the throttle 22 in response to an instruction from the control device 100.

The fuel injection valve 30, the common rail 40, and the pump 41 communicate with each other through a pipe. The fuel (diesel fuel is used as fuel in the present embodiment) stored in the fuel tank 42 mounted on the vehicle is fed under pressure to the common rail 40 by the pump 41 and is supplied to the common rail 40 And is supplied to the fuel injection valve 30 after the pressure becomes high. A plurality of fuel injection valves 30 according to the present embodiment are arranged in the engine main body 10 so as to inject fuel directly to the respective cylinders 11. [

The EGR passage 50 is a passage through which a part of the exhaust gas discharged from the cylinder 11 is recirculated to the cylinder 11. Thereafter, the exhaust introduced into the cylinder 11 may be referred to as EGR gas. The EGR passage 50 according to the present embodiment connects between the passage of the intake passage 20 and the passage of the exhaust passage 21. [ The EGR valve 51 is disposed in the EGR passage 50. The EGR valve 51 receives an instruction from the control device 100 and opens and closes it to adjust the amount of EGR gas.

The turbocharger (60) is a device for compressing the air sucked into the internal combustion engine (5). The turbocharger 60 includes a turbine 61 disposed in the exhaust passage 21 and a compressor 62 disposed in the intake passage 20. The turbine 61 is disposed in the exhaust passage 21, The turbine 61 and the compressor 62 are connected by a connecting member. When the turbine 61 is rotated by receiving force from the exhaust passing through the exhaust passage 21, the compressor 62 connected to the turbine 61 also rotates. As the compressor 62 rotates, the air in the intake passage 20 is compressed. Thereby, the air flowing into the cylinder 11 is supercharged. The intercooler 70 is disposed on the downstream side of the compressor 62 of the intake passage 20 and on the upstream side of the throttle 22. The refrigerant is introduced into the intercooler 70. The intercooler 70 cools the air in the intake passage 20 by the refrigerant introduced into the intercooler 70. The control device 100 controls the flow rate of the refrigerant introduced into the intercooler 70. [

The air flow sensor 80 is a sensor for detecting the amount of air (g / s) of the intake passage 20. The air flow sensor 80 transmits the detection result to the control device 100. The air flow sensor 80 according to the present embodiment is disposed on the upstream side of the compressor 62 of the intake passage 20 but the location of the air flow sensor 80 is not limited to this. The temperature sensor 81 is a sensor for detecting the temperature of the air in the intake passage 20. The temperature sensor 81 transmits the detection result to the control device 100. The temperature sensor 81 according to the present embodiment is disposed at a portion on the downstream side of the throttle 22 of the intake passage 20. The location of the temperature sensor 81 is not limited to this. The inside pressure sensor 82 is a sensor for detecting the inside pressure of the inside of the cylinder 11. The internal pressure sensor 82 transmits the detection result to the control device 100. The inside pressure sensor 82 according to the present embodiment is disposed in the engine main body 10. The fuel property sensor 83 is a sensor for detecting the property of the fuel. The fuel property sensor 83 transmits the detection result to the control device 100. The fuel property sensor 83 according to the present embodiment is disposed in the fuel tank 42 and detects the fuel property of the fuel tank 42. However, the location of the fuel property sensor 83 is not limited thereto. In addition to these sensors, the internal combustion engine 5 also includes various sensors such as a crank position sensor.

The control device 100 is an apparatus for controlling the internal combustion engine 5. The control device 100 according to the present embodiment controls the throttle 22 of the internal combustion engine 5, the fuel injection valve 30, the pump 41, the EGR valve 51 and the intercooler 70. [ Further, the control device 100 calculates the ignition delay time of the fuel and controls the injection timing of the fuel based on the calculated ignition delay time (hereinafter, this control processing will be referred to as ignition delay time calculation control). In this embodiment, as an example of the control apparatus 100, an electronic control apparatus (hereinafter, referred to as &quot; control apparatus &quot;) 101 including a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102 and a RAM Electronic Control Unit (ECU). In addition, each step of each flow chart described later is executed by the CPU 101. [ The ROM 102 and the RAM 103 have a function as a storage unit for storing information necessary for the operation of the CPU 101. [

Next, details of the ignition delay time calculation control of the control device 100 will be described using a flowchart. 2 is a diagram showing an example of a flowchart when control device 100 executes ignition delay time calculation control. The control device 100 repeatedly executes the flowchart of Fig. 2 at a predetermined cycle. First, the control device 100 acquires the cetane number CN of the fuel (step S10). Here, the cetane number refers to an index indicating the ignitability. The larger the value, the more easily the fuel is ignited. The smaller the value, the more difficult the ignition of the fuel. The control device 100 according to the present embodiment acquires the cetane number based on the detection result of the fuel property sensor 83. [ Further, as a specific method for obtaining the cetane number from the detection result of the fuel property sensor 83, a known method can be applied, and a detailed description will be omitted.

The specific method of obtaining the cetane number by the control device 100 is not limited to the above-described method. As another example, the lower the cetane number, the more the misfire tends to occur in the internal combustion engine 5. Therefore, the lower the cetane number, the greater the number of misfires (i.e., the misfire frequency) in a predetermined period. Therefore, the control apparatus 100 can detect the number of misfires during a predetermined period using a known method, and obtain the cetane number based on the detection result.

After step S10, the control device 100 calculates the ignition energy Ei based on the cetane number obtained in step S10 (step S20). The ignition energy refers to the energy required for ignition (specifically compression ignition) of the fuel in the cylinder 11. More specifically, the ignition energy refers to the energy required for the fuel to be injected from the fuel injection valve 30 into the cylinder 11, Refers to thermal energy that is required to be given to the air in the cylinder 11 during the period until the fuel becomes ignited.

More specifically, step S20 of the present embodiment is executed as follows. 3 (a) is a schematic diagram showing an example of a map defined by associating the ignition energy with the cetane number. The curve shown in FIG. 3 (a) shows the ignition energy Ei, and a lower value is adopted as the cetane number CN increases. That is, the map of FIG. 3 (a) is a map defining the ignition energy associated with the cetane number so that the ignition energy decreases as the cetane number increases. The map of FIG. 3 (a) is obtained in advance by experiment, simulation, and the like, and is stored in the storage unit. In step S20, the control device 100 extracts the ignition energy corresponding to the cetane number acquired in step S10 from the map of FIG. 3A and temporally stores the extracted ignition energy in the storage section, Thereby obtaining the ignition energy. For example, when the cetane number obtained in step S10 is A, the control device 100 acquires the value of B as the ignition energy. For example, the control apparatus 100 calculates the ignition energy based on a predetermined arithmetic expression. For example, the ignition energy is calculated based on the predetermined arithmetic expression, You may.

After step S20, the control device 100 calculates the in-cylinder energy integrated value Ea, which is the integrated value of the in-cylinder energy (step S30). The in-cylinder energy integration value refers to the integrated value of the energy (i.e., the in-cylinder energy) given in the cylinder 11 (i.e., in the cylinder) after the fuel is injected into the cylinder 11. To explain this in another expression to facilitate understanding, the in-cylinder energy integrated value refers to the integrated value of the energy (in-cylinder energy) given in the cylinder from the fuel injection start time in the cylinder 11, Means the accumulated heat energy given to the air, the fuel, and the mixer (fuel + air) in the cylinder 11 as the starting point of the fuel injection start point in the cylinder 11 as the starting point of the accumulation.

The concrete execution method of step S30 is not particularly limited as long as it can calculate the integrated energy value in the cylinder. However, the control apparatus 100 according to the present embodiment calculates the in-cylinder energy integrated value by the following method as an example do. Specifically, the control apparatus 100 according to the present embodiment calculates the in-cylinder energy integrated value based on the in-cylinder pressure (the pressure in the cylinder 11) and the in-cylinder temperature (the temperature in the cylinder 11). More specifically, the control apparatus 100 calculates the in-cylinder energy integrated value Ea based on Equation 1 (which is known as Livengood-Wu equation) shown below. The expression Livengood-Wu in the expression (1) is an expression for calculating the energy integration value in the tube based on the tube internal pressure and the tube internal temperature, and the storage section of the control device 100 stores in advance.

In Equation (1),? 0 is the time at which the fuel is injected into the cylinder 11, which is the time at which the fuel injection valve 30 injects the fuel. This will be described later, but the control apparatus 100 according to this embodiment executes step S30 until it is determined in step S40 that ignition has occurred. Therefore, in this embodiment, tau 1 is a time at which it is determined that ignition occurs in step S40. Therefore, the in-cylinder energy integrated value Ea relating to the present embodiment may be regarded as the integrated value of the in-cylinder energy during the period from when the fuel is injected into the cylinder 11 until it is determined that ignition has occurred.

In Equation (1), P is the internal pressure and T is the internal temperature. The control apparatus 100 according to the present embodiment acquires the internal pressure based on the detection result of the internal pressure sensor 82. [ The specific method of obtaining the internal pressure is not limited to this. For example, the control device 100 may acquire the internal pressure based on the index correlated with the internal pressure. Further, the control device 100 according to the present embodiment acquires the in-cylinder temperature based on the index correlated with the in-cylinder temperature. As an example of this indicator, the controller 100 uses the temperature of the air in the intake passage 20 (air temperature) and the load of the internal combustion engine 5. In addition, the higher the air temperature, the higher the temperature in the cylinder, and the higher the load, the higher the cylinder temperature. In this case, a map is stored in the storage unit of the control device 100, in which the in-cylinder temperature is associated with the air temperature and the load (in this embodiment, the rotational speed is used as an example of the load). The control device 100 acquires the air temperature of the intake passage 20 based on the detection result of the temperature sensor 81 and acquires the revolution number of the internal combustion engine 5 based on the detection result of the crank position sensor . The control device 100 extracts the in-cylinder temperature from the map of the storage section based on the acquired air temperature and the number of revolutions, and uses the extracted in-cylinder temperature as the in-cylinder temperature T of the equation (1).

The method of obtaining the in-cylinder temperature by the control apparatus 100 is not limited to the above method. For example, the control apparatus 100 may acquire the in-cylinder temperature based on the in-cylinder pressure detected by the in-cylinder pressure sensor 82, because the inside pressure and the in-cylinder temperature are correlated, for example. Further, when the internal combustion engine 5 is provided with a temperature sensor capable of directly detecting the in-cylinder temperature, the control device 100 may acquire the in-cylinder temperature based on the detection result of the temperature sensor.

In Equation (1), a, b and n are predetermined constants. In the present embodiment, values a, b, and n corresponding to the fuel having a predetermined cetane number are used as a, b, and n in Equation (1). Specifically, in this embodiment, as an example of a predetermined cetane number, 53, which is a fuel having a general cetane number, is used. When a fuel having a cetane number of 53 is used, the values a, b and n satisfying the expression (1) are obtained in advance, and the values of a, b and n are used as a, b and n in the expression (1). As described above, the control apparatus 100 according to the present embodiment does not use different values depending on the cetane number, but uses a predetermined cetane number (specifically, the fuel is the general cetane number 53) as a, b, The values of a, b, and n (constants) corresponding to the fuel of the engine 1 are used.

After step S30, the control device 100 determines whether or not the in-cylinder energy integrated value Ea acquired in step S30 is equal to or greater than the ignition energy Ei acquired in step S20 (step S40). When the in-cylinder energy integration value Ea is determined to be equal to or greater than the ignition energy Ei (in the case of "YES"), the control device 100 also determines that the fuel in the cylinder 11 is ignited ). Control device 100 determines that ignition does not occur when the in-cylinder energy integration value Ea has not been determined to be equal to or greater than ignition energy Ei (in the case of "NO"). Further, if the control device 100 determines "NO" in the step S40, the control device 100 executes the step S30, and subsequently executes the step S40. As a result, the control apparatus 100 according to the present embodiment repeatedly executes the operation of the equation (1) related to the step S30 until it is determined as "YES " in the step S40.

If "YES" in the step S40, the control device 100 calculates the ignition delay time (step S50). The control apparatus 100 according to the present embodiment is configured such that the fuel is injected from the fuel injection valve 30 into the cylinder 11 and then the in-cylinder energy integration value Ea acquired in step S30 is supplied to the ignition The time required until the energy becomes equal to or greater than the energy Ei is calculated as the ignition delay time. Specifically, the control apparatus 100 according to the present embodiment acquires the time required until the determination process of the step S40 is determined to be "YES " after the fuel is injected from the fuel injection valve 30, And acquires the acquired time as the ignition delay time.

Step S50 will be described using the drawings as follows. FIG. 3 (b) is a schematic diagram for visually explaining a calculation method of the ignition delay time. The ordinate of FIG. 3 (b) represents the in-tube energy integration value Ea, and the abscissa represents the elapsed time from the start of injection. The inclined straight line shown in Fig. 3 (b) is a straight line indicating the time variation of the in-cylinder energy integration value, and rises from the horizontal axis toward the right side. Here, it is assumed that the in-cylinder energy integration value Ea becomes equal to or greater than the ignition energy Ei at the time when the elapsed time from the start of injection reaches C. In this case, it is determined at step C that step S40 is "YES " In this case, the control device 100 calculates the time C as the ignition delay time in step S50.

Referring to Fig. 2, after step S50, the control device 100 controls the fuel injection timing based on the ignition delay time calculated in step S50 (step S60). Specifically, the control device 100 corrects the injection timing of the fuel so that the index indicative of the combustion state of the internal combustion engine 5 such as the fuel consumption or the emission is an appropriate value in accordance with the ignition delay time calculated in step S50 have. More specifically, the ignition delay time serving as a reference (hereinafter referred to as a reference ignition delay time) is stored in the storage unit of the control device 100 in advance. In step S60, when the difference between the ignition delay time calculated in step S50 and the reference ignition delay time is larger (that is, the ignition delay time calculated in step S50 is longer than the preset reference ignition delay time) And the timing of injection is changing to a faster period. However, the specific control content of step S60 is not limited to this, as long as the fuel consumption and emission can be optimized in accordance with the ignition delay time calculated in step S50. After step S60, the control device 100 ends the execution of the flowchart.

The CPU 101 of the control device 100 executing the step S10 has a function as a cetane number acquisition section for acquiring the cetane number of the fuel used in the internal combustion engine 5. [ The CPU 101 executing the step S20 has a function as an ignition energy calculating section for calculating the ignition energy based on the cetane number. The CPU 101 executing the step S30 has a function as an in-cylinder energy integrated value calculating unit for calculating the in-cylinder energy integrated value. The CPU 101 executing the step S40 has a function as a judging section for judging whether or not the in-cylinder energy integrated value calculated by the in-cylinder energy integrated value calculating section is equal to or higher than the ignition energy calculated by the ignition energy calculating section And a function as an ignition determination section for determining whether or not an ignition has occurred based on the determination result. The CPU 101 executing the step S50 calculates an ignition delay time calculating section which calculates the time required until the in-cylinder energy integration value becomes equal to or higher than the ignition energy after the fuel is injected into the cylinder 11 As shown in Fig. The CPU 101 executing the step S60 has a function as a control section for controlling the fuel injection timing based on the ignition delay time calculated by the ignition delay time calculating section.

As described above, according to the control apparatus 100 of the present embodiment, it is possible to control the amount of energy required for the in-cylinder energy integration value to become equal to or higher than the ignition energy calculated based on the cetane number after the fuel is injected into the cylinder 11 The time can be calculated as the ignition delay time. Thereby, the ignition delay time according to the cetane number can be calculated with high accuracy.

The ignition delay time of the fuel is determined by analyzing the chemical composition such as the physical properties such as the viscosity of the fuel used in the internal combustion engine 5 and the composition ratio of the fuel using an analyzer, It is also possible to do. However, it is not easy to calculate the ignition delay time by the analyzer every time fuel is supplied by mounting such an analyzer in a vehicle. On the other hand, according to the control apparatus 100 of this embodiment, the ignition delay time according to the cetane number can be calculated by the electronic control unit (ECU), so that the mounting performance to the internal combustion engine 5 and the vehicle is good. As described above, the control apparatus 100 according to the present embodiment is highly likely to be used industrially because it can easily calculate the ignition delay time by the internal combustion engine 5 or the on-board (i.e., ECU) mounted on the vehicle I can tell.

Further, according to the control apparatus 100 of the present embodiment, since the fuel injection timing is controlled based on the ignition delay time calculated by the ignition delay time calculating section (step S60), the ignition delay time corresponding to the cetane number The injection timing of the fuel can be controlled based on this. Thereby, it is possible to suppress the deterioration of the combustion state such as the fuel consumption and the emission even when the cetane number fuel different from the cetane number originally assumed as the fuel of the internal combustion engine 5 is used.

Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to these specific embodiments, but various modifications and changes may be made within the scope of the present invention described in the claims.

5: Internal combustion engine
10: engine body
11: Cylinder
20: Intake passage
21: Exhaust passage
22: Throttle
30: Fuel injection valve
40: Common rail
50: EGR passage
51: EGR valve
60: supercharger
70: Intercooler
100: Control device

Claims (2)

An ignition energy calculation section for calculating, based on a cetane number of the fuel, ignition energy, which is energy required for ignition of the fuel in the cylinder of the internal combustion engine, based on a predetermined map or an arithmetic expression;
An in-cylinder energy integrated value calculation unit for calculating an integrated value of the in-cylinder energy, which is a value obtained by integrating the thermal energy given to the cylinder after the fuel is injected into the cylinder, based on the in-
And an ignition delay time calculating section for calculating the ignition delay time as a time required until the accumulated value of the energy in the cylinder becomes equal to or higher than the ignition energy after the fuel is injected into the cylinder. The method according to claim 1,
And a control unit for controlling an injection timing of the fuel based on the ignition delay time calculated by the ignition delay time calculation unit.

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