JP6459450B2 - Engine control device - Google Patents

Description

  The present invention relates to a control device for controlling a fuel pressure (fuel pressure) of an engine.

  2. Description of the Related Art Conventionally, a technique for controlling the injection pressure of fuel injected from an injector according to the operating state of an engine is known. For example, there is a control for reducing the fuel injection pressure in an acceleration operation state in which an accelerator pedal is depressed. The acceleration operating state can be determined based on the magnitude of the accelerator opening change amount obtained by subtracting the previous value from the current value of the accelerator opening. By such control, the fuel injection pressure is reduced at the time of shifting to an acceleration operation in which a supercharge delay of the supercharger is likely to occur, and fuel atomization and combustion speed are suppressed (see Patent Document 1).

Japanese Patent No. 4510704

  However, the amount of intake air introduced into the cylinder changes according to the running state of the vehicle and environmental conditions. Therefore, even in the same acceleration operation state, the fuel injection pressure suitable for the state is not always constant. For example, if the injection pressure when the outside air temperature is high and the injection pressure when it is low are set to be the same, the degree of progress of atomization and the change in the combustion speed due to the temperature will not be taken into consideration. The combustion state inside can be unstable. Such a technical problem may occur not only in the acceleration operation state but also in the deceleration operation state.

  In addition, in an engine equipped with an EGR (Exhaust Gas Recirculation) system, the in-cylinder oxygen concentration changes according to the amount of EGR introduced into the cylinder, so the time from when fuel is injected until ignition is changed. , The penetration of fuel spray (penetration) varies. If this penetration force is not properly controlled, spray droplets are likely to approach and adhere to the cylinder inner wall and piston of the engine, making it difficult to optimize the combustion state. Such a technical problem becomes more prominent as the path length and path volume of EGR gas increase, as in, for example, a dual loop EGR (an EGR system having both a high pressure EGR passage and a low pressure EGR passage).

  The present case has been devised in view of the above-described problems, and an object of the engine control device is to improve the in-cylinder combustion state. It should be noted that the present invention is not limited to this purpose, and is an operational effect that is derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

(1) The engine control device disclosed herein includes a calculation unit that calculates a deviation obtained by subtracting a measured value of the in-cylinder pressure from a target value of the in-cylinder pressure set based on the operating state of the engine. Moreover, the control part which lowers | hangs the fuel pressure (fuel pressure) of the said engine, so that the said deviation calculated by the said calculation part is large is provided. The control unit changes the fuel pressure largely as the reduction ratio of the transmission connected to the engine is small.
For example, when the deviation is in a positive range, the amount of decrease in the fuel pressure at the second speed is larger than the first speed.
It is preferable to do. Further, when the deviation is in a negative range, the fuel pressure at the second speed rather than the first speed.
It is preferable to increase the amount of increase. That is, the smaller the reduction ratio, the more the fuel pressure is corrected.
It is preferred to increase the amount.
The measured value is preferably a value acquired based on an actually measured value of a parameter correlated with the in-cylinder pressure. For example, an actual measurement value of a parameter correlated with the in-cylinder pressure may be used as it is as the measurement value, or an estimated value of the in-cylinder pressure based on the actual measurement value may be used as the measurement value.

(2) It is preferable that the said control part reduces the said fuel pressure, so that the absolute value is large when the said deviation is a positive range, and raises the said fuel pressure, so that the absolute value is large when the said deviation is a negative range.
That is, it is preferable that the fuel pressure is corrected to decrease if the measured value is larger than the target value, and the fuel pressure is corrected to increase if the measured value is smaller than the target value. At this time, it is preferable to increase the correction amount of the fuel pressure as the absolute value of the deviation is larger.

( 3 ) It is preferable that the said calculation part makes the combustion pressure measured with the cylinder pressure sensor the said measured value.
The in-cylinder pressure sensor may be a sensor that directly detects the in-cylinder pressure, or a sensor that indirectly detects the in-cylinder pressure by detecting internal stress on a cylinder inner wall or a side wall of a water jacket. May be.

( 4 ) It is preferable that the said calculation part estimates the said measured value based on the intake pressure measured with the intake manifold pressure sensor (intake manifold pressure sensor).
Here, the value of the combustion pressure measured by the in-cylinder pressure sensor is referred to as “measured value”, and the value estimated based on the intake pressure measured by the intake manifold pressure sensor is referred to as “estimated value”. Call. The calculation unit may calculate the deviation by subtracting one of the actually measured value and the estimated value from the target value, or subtract an average value of the actually measured value and the estimated value from the target value. Then, the deviation may be calculated. That is, the actual measurement value and the estimated value can be used together.

( 5 ) It is preferable that the calculation unit calculates the deviation at the ignition time of the engine. The ignition time of the engine can be defined using, for example, the pressure increase rate, heat generation rate, combustion rate, etc. in the cylinder.
( 6 ) It is preferable that the control unit controls the fuel pressure on the condition that a rapid acceleration request for rapidly accelerating the vehicle is detected based on a driving operation of the driver. For example, the condition may be that the time change rate of the accelerator opening is equal to or higher than a predetermined change rate.

  According to the engine control device disclosed herein, the penetration force of the fuel spray can be reduced by reducing the fuel pressure as the deviation increases. As a result, the ease of spreading of the fuel spray can be optimized in accordance with the delay in the rise of the in-cylinder pressure due to the intake transportation delay or the supercharging delay, and the combustion state in the cylinder can be improved.

It is a figure which illustrates the composition of the engine and engine control device of an embodiment. 3 is a coefficient map illustrating the relationship between a gear stage of a transmission, a deviation ΔP, and a coefficient K. It is an example of a flowchart which shows the procedure of rail pressure control. It is a graph for demonstrating the effect | action of rail pressure control, (A) is an accelerator opening, (B) is in-cylinder pressure, (C) shows the time-dependent fluctuation | variation of the coefficient K. FIG.

  An engine control apparatus as an embodiment will be described with reference to the drawings. The embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment, and can be selected or combined as necessary.

[1. engine]
The engine control device 1 of the present embodiment is an electronic control device of the engine 10 that includes the dual loop EGR system shown in FIG. FIG. 1 illustrates one of a plurality of cylinders provided in the engine 10. The engine 10 is a diesel engine using light oil as fuel. An intake port and an exhaust port are provided on the top surface of the cylinder, and an intake valve and an exhaust valve are provided in each port opening. Further, an in-cylinder injection valve 11 is provided at the upper part in the cylinder in a state where its tip protrudes toward the combustion chamber. The in-cylinder injection valve 11 is a direct injection injector that injects fuel into each cylinder, and each in-cylinder injection valve 11 is connected to a common rail 27 that is a common pressure accumulation chamber. A fuel pump 28 is connected to the common rail 27 to store high-pressure fuel. The fuel pressure (fuel pressure, rail pressure F) in the common rail 27 changes according to the output of the fuel pump 28.

  The fuel injection amount and injection timing supplied from the in-cylinder injection valve 11 are controlled by the engine control device 1. For example, when a control pulse signal is transmitted from the engine control device 1 to the in-cylinder injection valve 11, the nozzle hole of the in-cylinder injection valve 11 is opened only for a period corresponding to the magnitude of the control pulse signal. At this time, the fuel injection amount is an amount corresponding to the rail pressure F in the common rail 27 and the magnitude (drive pulse width) of the control pulse signal, and the fuel injection timing (injection timing) corresponds to the time when the control pulse signal is transmitted. Will be.

  The intake passage 12 and the exhaust passage 13 of the engine 10 are provided with a turbocharger 14 (supercharger) for supercharging by forcibly sending the air on the intake passage 12 into the cylinder using the exhaust pressure. Is done. The turbocharger 14 has a structure in which the rotating shafts of the turbine and the compressor are connected via a bearing. The turbine is disposed on the exhaust passage 13 and the compressor is disposed on the intake passage 12. The operating state of the turbocharger 14 is controlled by the engine control device 1 according to the operating state of the engine 10.

  In the intake passage 12, an air cleaner (filter) 16, a low pressure throttle valve 17, a turbocharger 14, an intercooler 18, and a high pressure throttle valve 19 are provided in this order from the upstream side. On the other hand, an exhaust purification device 15 is interposed in the exhaust passage 13 on the downstream side of the turbocharger 14. The exhaust purification device 15 includes a DOC (diesel oxidation catalyst) 15A, a DPF (diesel particulate filter) 15B, and the like.

  In addition, the engine 10 is provided with two EGR passages for recirculating a part of the exhaust gas to the intake side, that is, a high pressure EGR passage 20 and a low pressure EGR passage 23. The high-pressure EGR passage 20 is an EGR passage that connects portions closer to the cylinder than the turbocharger 14 in the intake passage 12 and the exhaust passage 13, and is located downstream of the turbocharger 14 (compressor) in the intake passage 12 and the exhaust passage. 13 is connected to the upstream side of the turbocharger 14 (turbine). In the high pressure EGR passage 20 of the present embodiment, the connection location (exit location) with the intake passage 12 is set downstream of the high pressure throttle valve 19. The high pressure EGR passage 20 is provided with a high pressure EGR cooler 21 and a high pressure EGR valve 22 (one of EGR valves). The amount of EGR gas introduced into the intake system via the high pressure EGR passage 20 (high pressure EGR amount) is an amount corresponding to the pressure of the EGR gas and the opening degree of the high pressure EGR valve 22.

  The low-pressure EGR passage 23 is an EGR passage that connects portions farther from the cylinder than the turbocharger 14 in the intake passage 12 and the exhaust passage 13, and is located upstream of the turbocharger 14 (compressor) in the intake passage 12 and the exhaust passage. 13 is connected to the downstream side of the turbocharger 14 (turbine). In the low-pressure EGR passage 23 of the present embodiment, the connection location (inlet location) with the exhaust passage 13 is set downstream of the exhaust purification device 15, and the connection location (exit location) with the intake passage 12 is low-pressure throttle. It arrange | positions rather than the valve 17 downstream. The low pressure EGR passage 23 is provided with a low pressure EGR filter 24, a low pressure EGR cooler 25, and a low pressure EGR valve 26 (one of EGR valves). The amount of EGR gas (low pressure EGR amount) introduced into the intake system via the low pressure EGR passage 23 is an amount corresponding to the pressure of the EGR gas and the opening degree of the low pressure EGR valve 26. The valve openings of the high pressure EGR valve 22 and the low pressure EGR valve 26 are variable, and are controlled by the engine control device 1 according to the operating state of the engine 10.

  The high-pressure throttle valve 19 is disposed upstream of the connection portion with the high-pressure EGR passage 20 in the intake passage 12 and downstream of the connection portion with the low-pressure EGR passage 23. Further, the low pressure throttle valve 17 is disposed upstream of the connection portion of the intake passage 12 with the low pressure EGR passage 23 and downstream of the air cleaner 16. Note that the amount of EGR passing through the high pressure EGR passage 20 has a characteristic of decreasing as the opening degree of the high pressure throttle valve 19 is increased. Similarly, the amount of EGR passing through the low pressure EGR passage 23 has a characteristic of decreasing as the opening degree of the low pressure throttle valve 17 is increased.

An engine speed sensor 31 that detects the engine speed Ne is provided in the vicinity of the crankshaft of the engine 10. Further, on the downstream side of the high-pressure throttle valve 19 in the intake passage 12, an intake manifold pressure sensor 32 that detects the pressure of intake air (intake manifold pressure P _IM ) introduced into the cylinder, and oxygen concentration (intake oxygen concentration in intake air) An oxygen concentration sensor 33 for detecting D) is provided. The detected intake oxygen concentration D is the same as the oxygen concentration in the atmosphere when the low pressure EGR amount and the high pressure EGR amount are zero, and decreases as the low pressure EGR amount and the high pressure EGR amount increase.

  At an arbitrary position of the vehicle, an accelerator opening sensor 34 that detects an accelerator pedal depression amount (accelerator opening APS), a shift position sensor 35 that detects an operation position SP of a shift lever, and a vehicle speed that detects a vehicle speed V. A sensor 36 is provided. The accelerator opening APS and its time change rate ΔAPS are parameters corresponding to the magnitude of output (torque) requested by the driver to the engine 10, for example. Further, the operation position SP of the shift lever corresponds to a transmission gear stage (for example, 1st speed, 2nd speed,..., 6th speed, etc.) of a transmission mounted on the vehicle.

In the vicinity of the in-cylinder injection valve 11 in the cylinder, a glow plug having a built-in cylinder pressure sensor 37 is provided. This glow plug is an ignition assist device that improves the ignitability by heating the air in the cylinder when the engine 10 is cold-started, for example. The in-cylinder pressure sensor 37 is a pressure sensor built in the glow plug, and detects an actual in-cylinder pressure P _CYL that is an actual combustion pressure. The common rail 27 is provided with a fuel pressure sensor 38 that detects the rail pressure F. Various information detected by the various sensors 31 to 38 is transmitted to the engine control device 1.

[2. Engine control unit]
A vehicle equipped with the engine 10 is provided with an engine control device 1 (Engine Electronic Control Unit). The engine control device 1 is an electronic control device that comprehensively controls a wide range of systems such as an ignition system, a fuel system, an intake / exhaust system, and a valve system related to the engine 10, and the amount of intake air supplied to each cylinder of the engine 10. The fuel injection amount, the fuel injection timing, the EGR amount, and the like are controlled. The engine control device 1 is connected to other electronic control devices (for example, transmission ECU, air conditioner ECU, brake ECU, vehicle body control ECU, body ECU, etc.) and various sensors 31 to 38 via an in-vehicle network.

  The engine control device 1 is an electronic device in which a processor (microprocessor) such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, and the like are integrated. It is a device. The processor is an arithmetic processing unit that incorporates a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (register group), and the like. The ROM, RAM, and nonvolatile memory are memory devices that store programs and working data. The control contents in the engine control device 1 are recorded in ROM, RAM, nonvolatile memory, and removable media as application programs, for example. When the program is executed, the contents of the program are expanded in the memory space in the RAM and executed by the processor.

  The engine control apparatus 1 of the present embodiment performs rail pressure control that increases or decreases the rail pressure F in the common rail 27 according to the traveling state of the vehicle. The traveling state of the vehicle is determined based on various information detected by various sensors 31 to 38, for example. The specific method for increasing / decreasing the rail pressure F is arbitrary. For example, a method for increasing / decreasing the output of the fuel pump 28 or a rail pressure control valve provided in the return path from the common rail 27 to the fuel pump 28 side. A technique for controlling the opening can be employed.

In the rail pressure control, the rail pressure F is controlled based on the deviation ΔP between the in-cylinder pressure target value P _TGT and the measured value P _MEA . For example, the rail pressure F is corrected in the decreasing direction in an operation state in which the measured value P _MEA is smaller than the target value P _TGT of the in-cylinder pressure. On the other hand, in an operating state where the measured value P _MEA is larger than the target value P _TGT of the in-cylinder pressure, the rail pressure F is corrected in the increasing direction. Thereby, the penetration force of the fuel spray is optimized according to the actual pressure in the cylinder, and the combustion state is improved.

  The engine control device 1 is provided with a calculation unit 2 and a control unit 6 as elements for performing rail pressure control. Each of these elements may be realized by an electronic circuit (hardware), or may be programmed as software. Alternatively, a part of these functions may be provided as hardware and the other part may be software. The software may be recorded and stored in a ROM or an auxiliary storage device in the engine control device 1 or may be recorded in a recording medium that can be read by the engine control device 1.

[2-1. Calculation unit]
The calculation unit 2 calculates a deviation ΔP used in rail pressure control. The calculation unit 2 includes an actual in-cylinder pressure acquisition unit 3, a target in-cylinder pressure calculation unit 4, and a deviation calculation unit 5.
The actual in-cylinder pressure acquisition unit 3 acquires the actual measured value P _MEA of the in-cylinder pressure. The measured value P _MEA here includes both the “actual value” and the “estimated value” of the in-cylinder pressure, and also includes an “calculated value” calculated based on these values. That is, not only the actual in-cylinder pressure P _CYL actually measured by the in-cylinder pressure sensor 37 but also the estimated value of the in-cylinder pressure estimated based on the actually measured values of the parameters that affect the combustion state of the engine 10 are measured values P _MEA. It can be one of

For example, the estimated value of the estimated in-cylinder pressure based on the intake manifold pressure P _IM detected by the intake manifold pressure sensor 32 is one of the measured values P _MEA. In this case, it is preferable to estimate the measured value P _MEA not only based on the intake manifold pressure _PIM but also based on the intake oxygen concentration D, the intake air temperature, the rotational speed of the turbocharger 14, the coolant temperature, the EGR gas amount, and the like. Further, when the measured value of the in-cylinder pressure is used as the measured value P _MEA , the actual in-cylinder pressure P _CYL detected by the in-cylinder pressure sensor 37 may be used as it is as the measured value P _MEA . Further, it may be used an average value between the estimated value and the actual cylinder pressure P _CYL from the intake manifold pressure P _IM as a measurement value P _MEA. The information of the measured value P _MEA acquired here is transmitted to the deviation calculation unit 5.

The measured value _PMEA obtained by the actual in-cylinder pressure acquisition unit 3 represents the in-cylinder pressure at a preset timing within the combustion cycle of the engine 10. The predetermined timing here can be arbitrarily set, and may be a timing at which the piston reaches compression top dead center, or the ignition time [combustion rate (mass ratio of burned fuel out of all fuels) Or the time of combustion center of gravity (the time when the combustion rate becomes 50%). In the present embodiment, the deviation ΔP is calculated based on the target value P _TGT and the measured value P _{MEA at} the ignition time of the engine 10.

The target in-cylinder pressure calculation unit 4 calculates a target value P _TGT for the in-cylinder pressure based on the operating state of the engine 10. For example, a rotational load map of the engine 10 is preset in the target in-cylinder pressure calculation unit 4, and a target value P _{TGT of the in-} cylinder pressure is calculated based on this rotational load map. The rotational load map defines at least the relationship among the engine rotational speed Ne, the engine load Ec, and the target value P _TGT, and preferably defines a four-way relationship in which the engine coolant temperature is added thereto. The in-cylinder pressure target value P _TGT defined on the rotational load map corresponds to a standard in-cylinder pressure in a steady operation state of the engine 10. The engine load Ec is a parameter corresponding to an output request for the engine 10, and is based on, for example, the accelerator opening APS, the vehicle speed V, the intake air amount, the intake manifold pressure P _IM , the outside air temperature, the outside air pressure, the engine coolant temperature, and the like. Calculated. Information on the target value P _TGT calculated here is transmitted to the deviation calculation unit 5.

The deviation calculation unit 5 calculates a deviation ΔP of the measurement value P _MEA with the target value P _TGT as a reference. The deviation ΔP has a value obtained by subtracting the measured value P _MEA from the target value P _TGT as shown in the following Equation 1. When the measured value P _MEA coincides with the target value P _TGT , that is, in the steady operation state of the engine 10, the deviation ΔP becomes zero. On the other hand, if the measured value P _MEA is smaller than the target value P _TGT, ΔP becomes a positive value, and the absolute value of ΔP increases as the measured value P _MEA is smaller. Further, if the measured value P _MEA is larger than the target value P _TGT, ΔP becomes a negative value, and as the measured value P _MEA is larger, the absolute value of ΔP increases. Information on the deviation ΔP calculated here is transmitted to the control unit 6.

[2-2. Control unit]
The control unit 6 performs rail pressure control. The control unit 6 is provided with a condition determination unit 7 and a rail pressure control unit 8.
The condition determination unit 7 determines a start condition and an end condition for performing rail pressure control. The start condition is, for example, that the following condition 1 is satisfied. Condition 1 is to determine whether or not there is a sudden acceleration request for rapidly accelerating the vehicle. For example, when the time change rate of the accelerator opening APS is equal to or greater than a predetermined positive value, it is determined that there is a sudden acceleration request. The Conditions 2 to 4 are additional conditions, and the rail pressure control may be started when all the conditions 1 to 4 are satisfied.

= Rail pressure control start condition =
Condition 1: A sudden acceleration request for rapidly accelerating the vehicle is detected. Condition 2: The accelerator opening APS is equal to or greater than a predetermined opening. Condition 3: An acceleration operation is performed from a low-load driving condition. Condition 4: The vehicle speed V is a predetermined vehicle speed. Running at V ₀ or higher

In addition, the rail pressure control end condition is, for example, that any of the following conditions 5 to 8 is satisfied.
= Rail pressure control end condition =
Condition 5: The elapsed time from the start of control is a predetermined time or more Condition 6: The intake manifold pressure P _IM (measured value) has reached the target intake manifold pressure P _TGT (target value) Condition 7: The vehicle speed V is less than the predetermined vehicle speed V ₀ Condition 8: ΔP is almost zero

The target intake manifold pressure P _{TGT in} condition 6 is calculated based on the operating state of the engine 10. For example, a rotational load map of the engine 10 is preset in the condition determination unit 7, and the target intake manifold pressure P _TGT is calculated based on the rotational load map. The rotational load map defines at least the relationship among the engine speed Ne, the engine load Ec, and the target intake manifold pressure _PTGT, and preferably defines a four-way relationship including the engine coolant temperature. The value of the target intake manifold pressure P _TGT defined on a rotating load map corresponds to the standard intake manifold pressure P _IM in the steady operating state of the engine 10.

The rail pressure control unit 8 performs rail pressure control based on the deviation ΔP calculated by the calculation unit 2. Here, a reference rail pressure F _RAIL based on the operating state of the engine 10 is calculated, and a coefficient K for correcting the reference rail pressure F _RAIL is calculated. The rail pressure F in the common rail 27 is controlled based on the reference rail pressure F _RAIL and the coefficient K.
For example, a rotational load map of the engine 10 is preset in the rail pressure control unit 8, and the reference rail pressure F _RAIL is calculated based on this rotational load map. The rotational load map defines at least the relationship between the engine speed Ne, the engine load Ec, and the reference rail pressure F _RAIL, and preferably defines a four-way relationship including the engine coolant temperature. The value of the reference rail pressure F _RAIL defined on a rotating load map corresponds to a standard reference rail pressure F _RAIL in the steady operating state of the engine 10.

  The rail pressure control unit 8 is preset with a coefficient map in which at least the relationship between the deviation ΔP and the coefficient K is defined, and the coefficient K is calculated based on this coefficient map. As shown in FIG. 2, the coefficient map of this embodiment defines a three-way relationship of deviation ΔP, shift lever operating position SP, and coefficient K. On this coefficient map, the characteristic is such that the coefficient K is 1 when the deviation ΔP is zero, and the coefficient K decreases in the range greater than 0 and less than 1 as the deviation ΔP increases in the positive range. Is given. Further, as the deviation ΔP decreases in the negative range, the characteristic that the coefficient K increases in the range of more than 1 and less than 2 is given. Such a characteristic is a characteristic that does not depend on the operation position SP (that is, the reduction ratio) of the shift lever, that is, a characteristic common to each operation position SP.

  Further, on the above coefficient map, the relationship between the deviation ΔP and the coefficient K is determined for each shift lever operation position SP, and the shift lever operation position SP is closer to the high speed gear (the smaller the reduction ratio is). ), The characteristic that the value of the coefficient K changes greatly. For example, when the deviation ΔP is positive, a smaller coefficient K is given to the same deviation ΔP when the operation position SP is the second speed than when the operation position SP is the first speed. On the other hand, when the deviation ΔP is negative, a larger coefficient K is given to the same deviation ΔP when the operation position SP is the second speed than when the operation position SP is the first speed.

  That is, the coefficient map is given a characteristic that the value of the coefficient K changes more greatly as the speed reduction ratio of the transmission connected to the engine 10 is smaller. However, the value range of the coefficient K is set to 0 <K <2 so that the coefficient K is not changed too much. Note that the relationship between the coefficient K and the deviation ΔP as shown in FIG. 2 may be defined by expressing the coefficient K with a function including the deviation ΔP and the shift lever operating position SP as an index.

  Further, the decrease amount of the coefficient K per unit deviation (that is, the decrease amount of the coefficient K when the deviation ΔP is increased by a minute amount, in other words, the decrease slope of the coefficient K) has a large deviation ΔP. It is set to become smaller. That is, the coefficient K is given a characteristic that the gradient of the graph becomes gentler as the deviation ΔP increases. Therefore, in the rail pressure control of the present embodiment, the rail pressure F is controlled such that the amount of decrease in the rail pressure F per unit deviation decreases as the deviation ΔP increases.

Further, the rail pressure control unit 8 calculates an indicated rail pressure F _COM that is a control command value of the rail pressure F based on the reference rail pressure F _RAIL and the coefficient K. In the present embodiment, as shown in Expression 2, the product of the reference rail pressure F _RAIL and the coefficient K becomes the command rail pressure F _COM . Rail pressure control section 8, so that the actual rail pressure F approaches the instruction rail pressure F _COM, controls the opening of the output and the fuel pressure control valve of the fuel pump 28.

[3. flowchart]
FIG. 3 is a flowchart illustrating the procedure of rail pressure control, and is repeatedly executed in the engine control device 1 at a predetermined calculation cycle.
In step A1, various types of information are input to the engine control device 1. Here, for example, information such as accelerator opening APS, vehicle speed V, engine speed Ne, shift lever operation position SP, actual in-cylinder pressure P _CYL is acquired.

  In step A2, the condition determination unit 7 of the control unit 6 determines whether or not the rail pressure control start condition is satisfied. Here, for example, it is determined whether or not the time change rate of the accelerator opening APS is equal to or greater than a predetermined positive value. Here, if the rail pressure control start condition is satisfied, it is determined that there is a rapid acceleration request, a start condition satisfaction flag is set, and the process proceeds to step A3. On the other hand, if the rail pressure control start condition is not satisfied, the process proceeds to step A9. If the start condition satisfaction flag has already been set in the previous calculation cycle, step A2 is skipped to proceed to step A3 in order to determine the end condition of the rail pressure control.

In step A3, the condition determination unit 7 determines whether or not a rail pressure control end condition is satisfied. Here, for example, it is determined whether or not any of the above conditions 5 to 7 is satisfied. If this condition is satisfied, the process proceeds to step A9 to end the rail pressure control, and if not, the process proceeds to step A4.
In step A4, the actual in-cylinder pressure acquisition unit 3 acquires the measured value P _MEA of the in-cylinder pressure. When using an estimate of the in-cylinder pressure is measured value P _MEA is estimated based on the intake manifold pressure P _IM detected by the intake manifold pressure sensor 32. Further, when the actually measured value of the in-cylinder pressure is used, the actual in-cylinder pressure P _CYL detected by the in-cylinder pressure sensor 37 is directly used as the measured value P _MEA .

In step A5, the target in-cylinder pressure calculation unit 4 calculates a target value P _TGT of the in-cylinder pressure. Since the target value P _TGT is calculated based on the rotational load map of the engine 10, the target value P _TGT is a value corresponding to the engine rotational speed Ne, the engine load Ec, the engine coolant temperature, and the like at that time. In Step A6, the deviation calculating unit 5 calculates a deviation ΔP between the target value P _{TGT of the in-} cylinder pressure and the measured value P _MEA according to the above equation 1.

In step A7, the rail pressure control unit 8 of the control unit 6 calculates a coefficient K for correcting the reference rail pressure F _RAIL . Here, for example, a coefficient map as shown in FIG. 2 is used, and a coefficient K having a value corresponding to the deviation ΔP at that time and the operation position SP of the shift lever is calculated.
In the subsequent step A8, a reference rail pressure F _RAIL is calculated based on the operating state of the engine 10, and a value obtained by multiplying the reference rail pressure F _RAIL by a coefficient K is calculated as the indicated rail pressure F _COM. as approaching the F _COM, the output of the fuel pump 28 is controlled.
In step A9, since the rail pressure control start condition is not satisfied or the end condition is satisfied, the value of the coefficient K is set to K = 1 and normal control is performed. That is, in this case, the output of the fuel pump 28 and the like are controlled so that the reference rail pressure F _RAIL is directly set to the command rail pressure F _COM and the actual rail pressure F approaches the command rail pressure F _COM .

[4. Action]
As shown in FIG. 4A, in the low load low rotation state (idling operation state) of the engine 10, if a rapid acceleration operation is performed between times t _{0 and} t ₁ , the accelerator opening APS increases. The engine load Ec increases. Further, the target value P _TGT of the in-cylinder pressure increases from time t ₀ so as to correspond to the increase in the accelerator opening APS. On the other hand, since the actual in-cylinder pressure is affected by the intake transportation delay and the supercharging delay, as shown in FIG. 4 (B), the measured value P _MEA is in response to an increase in the target value P _TGT . Slightly delayed and fluctuates to follow while taking a value lower than the target value P _TGT .

On the other hand, in the engine control apparatus 1 of the present embodiment, the deviation ΔP of the measured value P _MEA based on the in-cylinder pressure target value P _TGT is calculated, and a coefficient for correcting the reference rail pressure F _RAIL based on the deviation ΔP. K is calculated. As shown in FIG. 4C, the value of the coefficient K becomes a value smaller than 1 between times t _{0 and} t ₂ when the measured value P _MEA is smaller than the target value P _{TGT of the} in-cylinder pressure. As a result, rail pressure control in which the actual rail pressure F is corrected in a decreasing direction with respect to the reference rail pressure F _RAIL is performed between the times t ₀ and t ₂ . Thus, in the state where the actual in-cylinder pressure is lower than the target value P _TGT , the penetration force of the fuel spray is weakened, so that the approach and adhesion of the spray droplets to the cylinder inner wall and the piston are suppressed, and Combustion state is optimized.

In addition, if a deceleration operation is performed between time t _{3 and} t ₄ immediately after the sudden acceleration operation, the engine load Ec decreases as the accelerator opening APS decreases, and the target value P _{TGT of the in-} cylinder pressure also increases. Decrease. In contrast, the measured value P _MEA of the in-cylinder pressure slightly delayed with respect to decrease a change in the target value P _TGT, varies so as to follow while taking a value higher than the target value P _TGT. On the other hand, as shown in FIG. 4C, the value of the coefficient K becomes a value larger than 1 between times t _{3 and} t ₅ where the measured value P _MEA is larger than the target value P _{TGT of the} in-cylinder pressure. . As a result, the rail pressure control in which the actual rail pressure F is corrected in the increasing direction from the reference rail pressure F _RAIL is performed between the times t ₃ and t ₅ . Thus, in the state where the actual in-cylinder pressure is higher than the target value P _TGT , the penetration force of the fuel spray is strengthened, so that the local deviation of the fuel spray (for example, the local equivalent ratio becomes excessive) Non-uniform distribution) is suppressed, and the combustion state in the cylinder is optimized.

[5. effect]
(1) In the engine control apparatus 1 described above, the rail pressure F of the engine 10 is lowered as the deviation ΔP between the in-cylinder pressure target value P _TGT and the measured value P _MEA increases. Thus, the penetration force of the fuel spray can be reduced by reducing the rail pressure F when the actual measurement value P _MEA is lower than the target value P _TGT of the in-cylinder pressure. Therefore, the ease of spreading of the fuel spray can be optimized in accordance with the increase in the in-cylinder pressure due to the intake transportation delay or the supercharging delay, and the combustion state in the cylinder can be improved.
Further, when the actual measured value P _MEA is higher than the target value P _TGT of the in-cylinder pressure, the penetration force of the fuel spray can be increased by increasing the rail pressure F. Therefore, the ease of spreading of the fuel spray can be optimized in accordance with the delay in lowering the in-cylinder pressure due to the intake transportation delay or the supercharging delay, and the combustion state in the cylinder can be improved.

(2) In the engine control apparatus 1 described above, as shown in FIG. 2, the coefficient K is set smaller than 1 when the deviation ΔP is positive, and the coefficient K is set larger than 1 when the deviation ΔP is negative. Is done. Further, the value of the coefficient K is set so that the correction amount increases as the absolute value of the deviation ΔP increases. For example, if the deviation ΔP is positive, the larger the value, the smaller the value of the coefficient K is set. If the deviation ΔP is negative, the smaller the value, the larger the value of the coefficient K is set.
In this way, by increasing the correction amount as the absolute value of the deviation ΔP is larger, the actual measurement value P _MEA can be brought closer to or coincident with the target value P _TGT at an early _stage . Therefore, for example, the in-cylinder combustion state at the time of sudden acceleration or sudden deceleration where the in-cylinder pressure changes rapidly can be improved.

(3) In the engine control apparatus 1 described above, the value of the coefficient K is set based on not only the deviation ΔP but also the operation position SP of the shift lever. For example, as shown in FIG. 2, the value of the coefficient K is changed to a smaller value for the same deviation ΔP in a transmission gear stage with a small reduction ratio than in a transmission gear stage with a large reduction ratio. This is because in a state where the reduction ratio is small, the engine load Ec with respect to the accelerator operation tends to increase, and the amount of fuel injected from the in-cylinder injection valve 11 tends to increase. In this way, by increasing the correction amount of rail pressure F in the operating state where the fuel injection amount is likely to increase, the dispersibility of the droplet particles (the ease with which the fuel spray spreads) can be greatly changed, and the transient The combustion state in the cylinder in the state can be improved.
On the other hand, when the speed reduction ratio is large, the engine speed Ne is more likely to increase than the engine load Ec with respect to the accelerator operation, and the fuel injection amount is less likely to increase. In this way, in the operating state where the fuel injection amount is difficult to increase, the dispersion of droplet particles close to normal (standard operating state in the steady operating state of the engine 10) is reduced by reducing the correction amount of the rail pressure F. The combustion state in the cylinder in the transient state can be stabilized.

(4) In the engine control apparatus 1 described above, the actual in-cylinder pressure P _CYL detected by the in-cylinder pressure sensor 37 can be used as the measured value P _MEA . Thus, by controlling the rail pressure F using the pressure value reflecting the actual combustion state in the cylinder, the combustion state in the cylinder can be accurately controlled. Further, when only the actual in-cylinder pressure P _CYL is used as the measured value P _MEA , for example, it is not necessary to estimate the measured value P _MEA based on the intake manifold pressure P _IM , and the control configuration can be simplified.

(5) In the above-described engine control device 1, also the estimated value of the estimated in-cylinder pressure based on the intake manifold pressure P _IM detected by the intake manifold pressure sensor 32, it can be used as a measurement value P _MEA. Thus, by controlling the rail pressure F by using the intake manifold pressure P _IM, also can be easily improved combustion conditions within the cylinder in the engine 10 is not equipped with the cylinder pressure sensor 37. Further, the in-cylinder pressure sensor 37 is easily affected by the vibration of the engine 10, whereas the intake manifold pressure sensor 32 is not easily affected by such vibration. Therefore, the influence of the presence or absence of vibration on the rail pressure control can be reduced, and the combustion state in the cylinder can be accurately controlled.

(6) In the engine control apparatus 1 described above, the deviation ΔP is calculated based on the target value P _TGT and the measured value P _{MEA at} the ignition time of the engine 10. Thereby, it is possible to accurately grasp the combustion state without being influenced by the variation shape of the in-cylinder pressure that is different for each combustion cycle, and it is possible to improve the in-cylinder combustion state.

  (7) In the engine control apparatus 1 described above, whether or not there is a rapid acceleration request for suddenly accelerating the vehicle is determined as a rail pressure control start condition. For example, when the time change rate of the accelerator opening APS is equal to or greater than a predetermined positive value, it is determined that there is a rapid acceleration request, and rail pressure control is started. In this way, by starting rail pressure control with a sudden acceleration request as a trigger, rail pressure F can be corrected only in situations where intake transport delays or supercharging delays are likely to occur. The combustion state with respect to the supply delay can be improved. On the other hand, since rail pressure F is not corrected unless rapid acceleration is being performed, the ease of spreading of fuel spray is not changed excessively, and the combustion state in steady operation can be stabilized.

  (8) In the engine control apparatus 1 described above, the rail pressure F is controlled so that the amount of decrease in the rail pressure F per unit deviation decreases as the deviation ΔP increases. By such control, it is possible to improve the complete combustibility of the fuel spray, and in particular, it is possible to improve the complete combustibility of the fuel spray when the deviation ΔP is large. For example, if the fuel injection pressure is excessively reduced in an acceleration operation state where the deviation ΔP is relatively large, it is difficult for each droplet to completely burn due to the expanded particle size of the droplet, and soot generation may increase. Will increase. On the other hand, the larger the deviation ΔP, the gentler the decreasing gradient of the rail pressure F, so that the increase in droplet diameter can be suppressed while lowering the rail pressure F, and the fuel spray is completely combustible. The exhaust performance can be improved.

[6. Modified example]
Regardless of the embodiment described above, various modifications can be made without departing from the spirit of the invention. Each structure of this embodiment can be selected as needed, or may be combined appropriately.

In the above-described embodiment, the control of the diesel engine has been described in detail, but this control can also be applied to a gasoline engine. Further, the dual loop EGR system and the turbo system are not essential elements for the engine 10 to be subjected to rail pressure control, and these can be omitted. As long as the rail pressure F is controlled based on the deviation ΔP obtained by subtracting the measured value P _MEA from the target value P _{TGT of the in-} cylinder pressure set based on the operating state of the engine 10, the same as in the above-described embodiment. Thus, the same effects as those of the above-described embodiment can be achieved.

  In the above-described embodiment, the example in which the coefficient K is set using the coefficient map as shown in FIG. 2 is illustrated, but the specific correspondence relationship between the gear stage of the transmission, the deviation ΔP, and the coefficient K is not limited to this. . In addition to these parameters, a coefficient map using another parameter related to the operating state of the engine 10 as an argument may be used. For example, the coefficient K may be set with reference to the intake oxygen concentration D, the low pressure EGR amount, the high pressure EGR amount, the intake air amount, the engine cooling water temperature, the intake air temperature, and the like. By taking these parameters into consideration, the shape and speed of the tumble flow and swirl flow in the cylinder, the progress rate of the combustion reaction in the cylinder can be estimated more accurately, and the combustion state in the cylinder can be estimated. It can be improved more accurately.

Conditions 1 to 8 in the above-described embodiment list conditions relating to the vehicle speed V, engine load Ec, time, intake manifold pressure P _IM , accelerator opening APS, and its rate of change over time. It is possible to add. For example, information such as the engine speed Ne, the rotation speed of the turbocharger, and the intake oxygen concentration D may be used together, or the contents of the conditions may be changed according to the operation position SP of the shift lever. On the contrary, it is good also as a control structure which abbreviate | omits Condition 1-Condition 8, and always performs rail pressure control during the driving | running | working of a vehicle (state which is not an idling driving state). Even with such rail pressure control, the in-cylinder combustion state can be improved.

  In the above-described embodiment, rail pressure control for increasing or decreasing the rail pressure F in the common rail 27 has been described in detail, but the fuel pressure to be controlled is not limited to the rail pressure F in the common rail 27. For example, in the case of the engine 10 without the common rail 27, the pressure of fuel supplied to the in-cylinder injection valve 11 or the pressure of fuel injected from the in-cylinder injection valve 11 may be controlled. Even in such control, the penetration force of the fuel spray and the ease of spreading of the fuel spray can be optimized, and the combustion state in the cylinder can be improved.

DESCRIPTION OF SYMBOLS 1 Engine control apparatus 2 Calculation part 3 Actual cylinder pressure acquisition part 4 Target cylinder pressure calculation part 5 Deviation calculation part 6 Control part 7 Condition determination part 8 Rail pressure control part 10 Engine 11 In-cylinder injection valve 27 Common rail 28 Fuel pump 32 In manifold pressure Sensor 35 Shift position sensor 37 In-cylinder pressure sensor
SP operation position
F _RAIL reference rail pressure
K factor
P _CYL actual cylinder internal pressure
P _TGT target value
P _MEA measured value ΔP Deviation

Claims (6)

A calculation unit that calculates a deviation obtained by subtracting a measured value of the in-cylinder pressure from a target value of the in-cylinder pressure set based on an operating state of the engine;
A controller that lowers the fuel pressure of the engine as the deviation calculated by the calculator increases .
The engine control apparatus according to claim 1, wherein the control unit changes the fuel pressure more greatly as a reduction ratio of a transmission connected to the engine is smaller . 2. The control unit according to claim 1, wherein the control unit decreases the fuel pressure as the absolute value increases in a positive range and increases the fuel pressure as the absolute value increases in a negative range. Engine control device. The calculating unit, characterized in that the combustion pressure measured by the cylinder pressure sensor and the measured value, the engine control apparatus according to claim 1 or 2, wherein. The calculating unit, and estimates the measured value based on the intake pressure measured by the intake manifold pressure sensor, an engine control apparatus according to any one of claims 1-3. The calculating unit, and calculates the deviations in the ignition time of the engine, the engine control apparatus according to any one of claims 1-4. Wherein the control unit, based on the driver's driving operation, on condition that it detects abrupt acceleration demand for rapid acceleration of the vehicle, which comprises carrying out the control of the fuel pressure, any one of claims 1 to 5 The engine control apparatus according to item 1.

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