JP5370207B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, an engine control device described in Patent Document 1 below is known as a technology in such a field. This control device AD-converts a first type of detection value to be sampled at a predetermined time period and a second type of detection value to be sampled at a predetermined crank angle period by a single common AD converter. . When the AD conversion timings of the first type and second type detection values overlap, the AD conversion processing of the other detection value is waited until the AD conversion processing of one detection value ends. .

Japanese Patent Laid-Open No. 2003-243985

  However, when waiting for AD conversion processing occurs in the control device, the other detected value is acquired with a delay of the waiting time, and in the control using the other detected value, The real-time property of control is impaired. In view of such a problem, an object of the present invention is to provide a control device that can ensure real-time control of an internal combustion engine.

  The control apparatus for an internal combustion engine according to the present invention includes a first conversion process for AD-converting a detection value of the first sensor at a predetermined time period, and a second sensor at a predetermined crank angle period in synchronization with the crank angle of the internal combustion engine. An AD converter that performs AD conversion of the detected value of the detected signal, an estimation unit that estimates the detected value of the second sensor and obtains an estimated detected value, and a first sensor that has undergone the first conversion process. First control execution means for executing control based on the detection value, and second control execution means for executing control based on the detection value of the second sensor after the second conversion process or the estimated detection value obtained by the estimation means When the execution timing of the first conversion process overlaps with the execution timing of the second conversion process, the AD converter does not execute the second conversion process. The first conversion process is executed, and the second control execution means And executes a control based on the estimated detection value obtained by.

  According to this control device, when the execution timing of the first conversion process and the execution timing of the second conversion process overlap, the AD converter converts only the detection value of the first sensor by the first conversion process. To do. Then, the estimated detection value is obtained by the estimation means, and the control of the second control execution means is performed based on the estimated detection value. Therefore, by using the estimated detection value instead of the detection value without waiting for the AD conversion of the detection value of the second sensor, the real-time property of the control in the second control execution unit can be ensured. In this case, since the first conversion process by the AD converter is executed, the real-time property of the control in the first control execution means can be ensured.

  The second sensor may be an in-cylinder pressure sensor that detects the pressure in the cylinder in correspondence with the crank angle of the internal combustion engine. The pressure in the cylinder corresponding to the crank angle (in-cylinder pressure) can be used for various internal combustion engine controls, and real-time performance can be ensured in various controls.

  Further, the estimation means may employ the detection value obtained in the previous second conversion process as the estimated detection value when the crank angle of the internal combustion engine is within a predetermined range. Depending on the range of the crank angle, there is a range where the variation of the in-cylinder pressure is small. Therefore, in the crank angle range where the fluctuation of the in-cylinder pressure is small, even if the previous detection value is the estimated detection value, the deviation from the actual is small, and the processing load is larger than when the estimated detection value is obtained by calculation or the like. Can be suppressed.

  According to the control device for an internal combustion engine of the present invention, it is possible to ensure real-time control of the internal combustion engine.

It is a figure which shows the internal combustion engine to which the control apparatus of this invention is applied. It is a figure which shows the control apparatus of this invention. It is a figure which shows the in-cylinder pressure and the timing of a 1st and 2nd conversion process corresponding to a crank angle. It is a flowchart which shows the process by the control apparatus of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an engine 100 of a vehicle (automobile) 200 to which an engine control apparatus 1 according to an embodiment of the present invention is applied. The engine 100 shown in FIG. 1 burns a mixture of fuel and air in a combustion chamber 3a of a cylinder 3 formed in a cylinder block 2, and reciprocates a piston 4 in the combustion chamber 3a to generate power. It is what happens. The engine 100 may be configured as a multi-cylinder engine including a plurality of cylinders 3.

  The intake port of the combustion chamber 3 a is connected to the intake pipe 5, and the exhaust port of the combustion chamber 3 a is connected to the exhaust pipe 6. The intake valve Vi opens and closes the intake port, and the exhaust valve Ve opens and closes the exhaust port. The intake pipe 5 is connected to a surge tank 8. An intake passage is connected to the surge tank 8, and the intake passage is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (in this embodiment, an electronically controlled throttle valve) 10 is incorporated in the intake passage (between the surge tank 8 and the air cleaner 9). On the other hand, to the exhaust pipe 6, for example, a front-stage catalyst device 11a including a three-way catalyst and a rear-stage catalyst device 11b including, for example, a NOx storage reduction catalyst are connected.

  The engine 100 further includes an engine control ECU 20 and a number of sensors including a crank angle sensor 14, an in-cylinder pressure sensor 15, and an accelerator opening sensor 16 that are electrically connected to the engine control ECU 20. Yes. The engine control ECU 20 uses the various maps and the like stored in the storage device and also obtains a desired output based on the detection values and the like of the various sensors, so that the spark plug 7, the throttle valve 10, the injector 12, and the valve Vi are obtained. , Ve is controlled.

  The in-cylinder pressure sensor 15 includes a semiconductor element, a piezoelectric element, a magnetostrictive element, an optical fiber detection element, or the like, and is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3a. Each in-cylinder pressure sensor 15 outputs a pressure (in-cylinder pressure) applied to the pressure receiving surface in the combustion chamber 3a as a relative value with respect to the atmospheric pressure, and a voltage corresponding to the pressure applied to the pressure receiving surface (in-cylinder pressure). A detection value signal (a signal indicating the detection value) is supplied to the engine control ECU 20.

  Crank angle sensor 14 is a sensor that detects a rotation angle (crank angle) of a crankshaft that is rotationally driven in engine 100. The crank angle sensor 14 transmits the detected rotation angle of the crankshaft to the engine control ECU 20 as a crank angle signal.

The engine control device 1 shown in FIG. 2 is applied to the engine 100 as described above. As shown in FIG. 2, the engine control apparatus 1 includes the above-described engine control ECU 20, and includes various sensors that are electrically connected to the engine control ECU 20. For example, in addition to the crank angle sensor 14 and the in-cylinder pressure sensor 15, the engine control device 1 of the present embodiment includes a water temperature sensor 41 that measures the temperature of the cooling water of the engine 100, and the intake air amount to the cylinder 3. There are provided a number of sensors such as an air flow meter 42 that measures the oxygen concentration and an O ₂ sensor 43 that measures the oxygen concentration in the exhaust gas. In the following description, among the many sensors, the above-described sensors 14, 15, 41, 42, and 43 will be described as examples. The engine control ECU 20 performs various controls (for example, control of the ignition timing of the spark plug 7, control of the fuel injection amount) of each part of the engine based on the detection values obtained from the sensors 14, 15, 41, 42, 43, etc. , Opening / closing control of the valves Vi and Ve).

  The engine control ECU 20 includes a control processing CPU 30. The control processing CPU 30 is configured as a computer including a CPU core, ROM, RAM, communication circuit, AD conversion circuit, and the like. The control processing CPU 30 includes an AD conversion unit 31, an in-cylinder pressure estimation unit 32, an in-cylinder stroke determination unit 33, and a control processing unit 34. Each of these components 31 to 34 is configured by software such that hardware such as a CPU core, ROM, RAM, communication circuit, and AD conversion circuit constituting the control processing CPU 30 operates in accordance with a predetermined program. It is a component realized in For example, the AD conversion unit 31 is physically a known AD converter mainly composed of an AD conversion circuit included in the control processing CPU 30.

The AD conversion unit 31 has a predetermined time period (here, 4 ms period), a water temperature detection signal from the water temperature sensor 41, an air amount detection signal from the air flow meter 42, and an oxygen concentration from the O ₂ sensor 43. The signal is subjected to AD conversion (analog-digital conversion), and each detected value is input to the control processing unit 34. Hereinafter, such AD conversion processing performed in a predetermined time period may be referred to as “first conversion processing”.

  The in-cylinder pressure obtained by the in-cylinder pressure sensor 15 is information that should be acquired corresponding to each crank angle. Therefore, the AD conversion unit 31 synchronizes with the crank angle signal from the crank angle sensor 14 and outputs the in-cylinder pressure signal from the in-cylinder pressure sensor 15 at a predetermined crank angle cycle (here, 5 ° CA cycle). AD conversion is performed, and the in-cylinder pressure detection value after AD conversion is input to the control processing unit 34. Hereinafter, such AD conversion processing performed at a predetermined crank angle cycle may be referred to as “second conversion processing”.

  The in-cylinder pressure estimation unit 32 calculates an in-cylinder pressure estimated value instead of the in-cylinder pressure detection value and inputs it to the control processing unit 34 when the in-cylinder pressure detection value from the AD conversion unit 31 cannot be obtained. The details when the in-cylinder pressure detection value cannot be obtained from the AD conversion unit 31 will be described later. The in-cylinder stroke determination unit 33 recognizes the current crank angle and the in-cylinder stroke based on the crank angle signal from the crank angle sensor 14 and inputs the recognized crank angle and in-cylinder stroke to the in-cylinder pressure estimation unit 32.

  The control processing unit 34 performs various controls of each part of the engine based on each detection value (water temperature detection value, intake air amount detection value, oxygen concentration detection value) obtained in the first conversion process. Engine control based on information acquired in synchronization with time in this way may be referred to as “first control” below. In addition, the control processing unit 34 sets the in-cylinder pressure value obtained by the second conversion process of the AD conversion unit 31 or the in-cylinder pressure estimation value obtained by the in-cylinder pressure estimation unit 32 to any in-cylinder pressure value. Based on this, various control of each part of the engine is performed. The engine control based on the information acquired in synchronization with the crank angle as described above may be hereinafter referred to as “second control”. The control processing unit 34 has both the function as the first control execution unit and the function as the second control execution unit described in the claims.

  Subsequently, as shown in FIG. 3, the AD conversion processing by the AD conversion unit 31 takes a certain time (for example, 5 μs per channel). In particular, in the first conversion process, the detection values of a large number of sensors need to be processed, so the processing time of the first conversion process is relatively long. The second conversion process is also performed with a relatively short cycle. For example, when the engine speed is 5000 rpm, the second conversion process with a cycle of 5 ° CA is performed every 167 μs. Therefore, the timing of the first conversion process may overlap with the timing of the second conversion process. However, the AD conversion unit 31 cannot perform the first and second conversion processes at the same time, and if the second conversion process is activated during the execution of the first conversion process, the result of the first conversion process is All will be destroyed. If the result of the first conversion process is discarded, the first control process of the control processing unit 34 uses the result of the first conversion process acquired last time. , Fuel efficiency, and exhaust gas properties deteriorate.

  Therefore, when the timing of the first conversion process and the timing of the second conversion process overlap, the AD conversion unit 31 performs only the first conversion process without performing the second conversion process. Therefore, even when the timing of the first conversion process and the timing of the second conversion process overlap, the detection value after the process related to the first conversion process is normally input to the control processing unit 34. On the other hand, since the in-cylinder pressure detection value by the second conversion process cannot be obtained, the in-cylinder pressure estimation unit 32 calculates the in-cylinder pressure estimation value instead of the in-cylinder pressure detection value as described above and inputs it to the control processing unit 34. To do.

  At this time, the in-cylinder pressure estimation unit 32 calculates an estimated in-cylinder pressure value based on the crank angle and the in-cylinder stroke obtained from the in-cylinder stroke determination unit 33. Specifically, when the current crank angle is within a predetermined range, the in-cylinder pressure estimation unit 32 determines the in-cylinder pressure detection value (in-cylinder pressure before 5 ° CA) obtained in the previous second conversion process. Detected value) is adopted as the estimated cylinder pressure. The “predetermined range” is set in advance as a range in which the in-cylinder pressure can be regarded as substantially constant, as shown as region A in FIG. That is, the “predetermined range” may be set so as to substantially correspond to the crank angle range from the exhaust stroke to the intake stroke. In such a range, even if the previous in-cylinder pressure detection value is adopted as the in-cylinder pressure estimation value, the deviation from the actual is small, and the processing load is larger than when obtaining the in-cylinder pressure estimation value by calculation or the like. Can be suppressed. Here, instead of using the previous in-cylinder pressure detection value, a value based on a prepared in-cylinder pressure model may be employed as the estimated in-cylinder pressure value.

Further, the cylinder pressure estimation section 32, if the current crank angle is outside the predetermined range described above, using Equation (1) below, calculates the cylinder pressure estimate P _theta. This “outside the predetermined range” is a crank angle range in which the variation in the in-cylinder pressure is large, as shown as a region B in FIG. That is, “outside the predetermined range” generally corresponds to the crank angle range from the compression stroke to the combustion stroke.
P _θ = (1 / V _θ ^κ ) × <{1−exp [−a {(θ−θ0) / (θf−θ0)} ^{m + 1} ]} × (P _θf V _θf ^κ −P _θ0 V _θ0 ^κ ) + P _θ0 V _θ0 ^κ 〉… (1)

However,
P _θ : In-cylinder pressure at an arbitrary crank angle θ (in-cylinder pressure estimated value)
V _θ : In-cylinder volume at an arbitrary crank angle θ
P _θ0 : In-cylinder pressure at the combustion start timing θ0
V _θ0 : In-cylinder volume at combustion start timing θ0
P _θf : In-cylinder pressure at the combustion end timing θf
V _θf : In-cylinder volume at combustion end timing θf: Specific heat ratio a: Combustion speed m: Specified constant

According to this calculation method, the in-cylinder pressure at an arbitrary crank angle θ is estimated from two measured data of a combustion start timing θ0 (for example, −60 ° CA) and a combustion end timing θf (for example, 90 ° CA). Can do. Note that such an in-cylinder pressure estimation method is also disclosed in Japanese Patent Application Laid-Open No. 2007-32531.

  As a result, when the timing of the first conversion process and the timing of the second conversion process overlap, any of the in-cylinder pressure estimated values obtained as described above is replaced with the control processing unit 34 instead of the in-cylinder pressure detection value. The second control by the control processing unit 34 is performed based on the estimated in-cylinder pressure value.

  Next, specific processing for the control processing CPU 30 to acquire the in-cylinder pressure and perform engine control based on the in-cylinder pressure will be described with reference to the flowchart of FIG. When engine 100 is started, control processing CPU 30 repeats the processing shown in FIG. 4 at a predetermined crank angle cycle (here, 5 ° CA cycle) in synchronization with the crank angle signal from crank angle sensor 14. Do.

  First, the control processing CPU 30 determines whether or not the AD conversion unit 31 is executing the first conversion process when the timing of the second conversion process arrives (S101). Here, when the AD conversion unit 31 is not executing the first conversion process (No in S101), the AD conversion unit 31 executes the second conversion process of the in-cylinder pressure signal (S103), and the cylinder after AD conversion is performed. The internal pressure detection value is transmitted from the AD conversion unit 31 to the control processing unit 34 (S105). Then, the control processing unit 34 performs the second control based on this in-cylinder pressure detection value (S107). On the other hand, if the AD conversion unit 31 is executing the first conversion process in step S101 (Yes in S101), the AD conversion unit 31 stops the second conversion process of the in-cylinder pressure signal (S113). In this case, the AD conversion unit 31 continues the first conversion process being executed.

  Next, the in-cylinder stroke determination unit 33 determines whether or not the current crank angle is in the region B of FIG. 3 based on the crank angle signal (S115). Here, when the current crank angle is in the region B (Yes in S115), the in-cylinder pressure estimation unit 32 calculates the in-cylinder pressure estimated value from the above-described equation (1) based on the current crank angle (S117). ). On the other hand, when the current crank angle is not in the region B (when it is in the region A) in the process S115 (No in S115), the in-cylinder pressure estimation unit 32 detects the in-cylinder pressure by the second conversion process executed last time. The value is adopted as the estimated cylinder pressure (S119). Next, the in-cylinder pressure estimation unit 32 transmits the in-cylinder pressure estimated value determined in either of the processing S117 or S119 to the control processing unit 34 (S121). Then, the control processing unit 34 performs the second control based on the in-cylinder pressure estimated value (S107).

  In the process S113, the AD conversion unit 31 continues the first conversion process while stopping the second conversion process, and detects the detected values of the water temperature, the air amount, and the oxygen concentration after the AD conversion. 34. And the control process part 34 performs 1st control based on each detected value of water temperature, air volume, and oxygen concentration.

  According to the engine control device 1 described above, when the execution timing of the first conversion process overlaps with the execution timing of the second conversion process, the AD conversion unit 31 stops the second conversion process and performs the first conversion process. Continue processing. At this time, the in-cylinder pressure estimation value is obtained by the in-cylinder pressure estimation unit 32, and the in-cylinder pressure estimation value is used in the second control by the control processing unit 34. Therefore, the real-time property of the second control based on the in-cylinder pressure can be ensured by using the in-cylinder pressure estimated value instead of the in-cylinder pressure detection value without waiting for the second conversion process. On the other hand, since the first conversion process by the AD conversion unit 31 is continued, the result of the first conversion process is not discarded, and the real-time property of the first control is ensured. Further, according to this process, even when the timings of the first and second conversion processes overlap, it is possible to cope with one AD converter, and separate AD converters for the first and second conversion processes. There is no need to provide it. Therefore, the control processing CPU 30 has only one AD converter, and the CPU structure can be prevented from becoming complicated.

  Further, the calculation of the in-cylinder pressure estimated value using the above-described mathematical formula (1) is complicated in calculation, and thus the processing load on the control processing CPU 30 is high. However, the in-cylinder pressure estimation unit 32 does not perform calculation within the crank angle range where the variation in the in-cylinder pressure is small (region A in FIG. 3), and uses the previous in-cylinder pressure detection value as the in-cylinder pressure estimation value. Therefore, the processing load of the control processing CPU 30 can be suppressed as compared with the case where the calculation is performed with the crank angle in the entire range.

DESCRIPTION OF SYMBOLS 1 ... Engine control apparatus, 3 ... Cylinder, 14 ... Crank angle sensor, 15 ... In-cylinder pressure sensor (2nd sensor), 30 ... Control processing CPU, 31 ... AD converter (AD converter), 32 ... In-cylinder pressure estimation Part (estimating means), 34 ... control processing part (first control execution means, second control execution means), 41 ... water temperature sensor (first sensor), 42 ... air flow meter (first sensor), 43 ... O ₂ sensors (first sensor), 100... Engine (internal combustion engine).

Claims (3)

First conversion processing for AD conversion of the detection value of the first sensor at a predetermined time period, and second conversion for AD conversion of the detection value of the second sensor at a predetermined crank angle period in synchronization with the crank angle of the internal combustion engine An AD converter that performs processing;
Estimating means for estimating a detection value of the second sensor and obtaining an estimated detection value;
First control execution means for executing control based on a detection value of the first sensor after the first conversion processing;
Second control execution means for executing control based on the detection value of the second sensor after the second conversion process or the estimated detection value obtained by the estimation means;
An internal combustion engine control device comprising:
When the execution timing of the first conversion process and the execution timing of the second conversion process overlap,
The AD converter performs the first conversion process without performing the second conversion process,
The control apparatus for an internal combustion engine, wherein the second control execution means executes control based on the estimated detection value obtained by the estimation means. The second sensor is
2. The control device for an internal combustion engine according to claim 1, wherein the control device is an in-cylinder pressure sensor that detects a pressure in a cylinder in correspondence with a crank angle of the internal combustion engine. The estimation means includes
3. The internal combustion engine according to claim 2, wherein when the crank angle of the internal combustion engine is within a predetermined range, the detection value obtained in the previous second conversion process is adopted as the estimated detection value. Control device.

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