JP2007100653A - Control device of compressed self-ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the ignition timing while maintaining amenity in a compressed self-ignition type internal combustion engine. <P>SOLUTION: An ECU 100 executes ignition timing control processing. In the ignition timing control processing, a reference value (a) is acquired as a threshold value for regulating a high area and a low area of sensitivity of the actual ignition timing CAr to the injection timing CAi of fuel. When the ignition timing CAi at present time belongs to an area on the ignition timing advance side more than the reference value (a) being such a low area of the sensitivity, the ECU 100 controls the actual ignition timing CAr by the valve closing timing CAv of an intake valve 207. While, when the the injection timing Cai belongs to an area on the ignition timing delay side more than the reference value (a) being such a high area of the sensitivity, the ECU 100 controls the actual ignition timing CAr by the injection timing CAi. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technical field of a control device for a compression self-ignition internal combustion engine for controlling a compression self-ignition internal combustion engine having a variable valve mechanism such as VVT (Variable Valve Timing).

  In this type of technical field, one that controls the fuel injection timing has been proposed (see, for example, Patent Document 1). According to the engine combustion control method and apparatus (hereinafter referred to as “conventional technology”) disclosed in Patent Document 1, the ignition timing of fuel in each cylinder is estimated, and each cylinder is estimated based on this estimated value. It is said that variations in combustion can be reduced by correcting the injection timing at.

  A technique has also been proposed in which the injection timing when the in-cylinder pressure is controlled high by the variable valve mechanism is retarded with respect to the injection timing when the in-cylinder pressure is controlled low (see, for example, Patent Document 2). ).

  A technique for controlling the compression pressure by operating the valve opening / closing timing in accordance with the operating state has also been proposed (see, for example, Patent Document 3).

  In addition, when the ignition timing of at least one cylinder of the multi-cylinder internal combustion engine deviates from the target, a technique for changing the intake valve closing timing of all cylinders has also been proposed (see, for example, Patent Document 4).

  As a technique similar to the conventional technique, a technique for controlling the injection timing so that the estimated ignition timing becomes the target ignition timing has been proposed (for example, see Patent Document 5).

JP 2002-221071 A JP 2003-83141 A Japanese Patent Laid-Open No. 11-257108 JP 2005-2803 A JP-A-11-125141

  The ignition timing of the fuel in the compression ignition type internal combustion engine needs to be controlled in real time from the viewpoint of maintaining the comfort of the vehicle. However, in the compression self-ignition internal combustion engine, there is an injection timing region in which the sensitivity to the ignition timing is relatively low. In such a region, it is difficult to control the fuel ignition timing in real time. That is, the conventional technique has a technical problem that the comfort of the vehicle may be impaired.

  This invention is made | formed in view of the problem mentioned above, and makes it a subject to provide the control apparatus of the compression self-ignition internal combustion engine which can maintain comfort.

  In order to solve the above-described problems, a control device for a compression self-ignition internal combustion engine according to the present invention (hereinafter referred to as a “control device” where appropriate) includes injection means for injecting fuel and at least a closing timing of an intake valve. Is a control device for a compression self-ignition internal combustion engine for controlling a compression self-ignition internal combustion engine having a variable A, and a target ignition timing specifying means for specifying a target ignition timing of the injected fuel, and the injection An actual ignition timing specifying means for specifying an actual fuel ignition timing, a difference calculating means for calculating a difference between a value defining the target ignition timing and a value defining the actual ignition timing, and corresponding to the actual ignition timing In accordance with the fuel injection timing, (i) a first control for controlling the valve closing timing of the intake valve based on the difference so that the actual ignition timing becomes the target ignition timing; and (ii) the actual ignition. The timing is the target ignition timing The selection means for selecting at least one of the second controls for controlling the fuel injection timing based on the difference, and the actual ignition timing for controlling the actual ignition timing by executing at least one of the selected controls. And a timing control means.

  The “compression self-ignition internal combustion engine” according to the present invention is a concept that encompasses an engine that converts explosive power obtained by self-igniting fuel into power, and typically refers to a diesel engine for a vehicle. . Furthermore, the compression self-ignition internal combustion engine according to the present invention includes fuel injection means and at least the closing timing of the intake valve is variable.

  Here, the fuel injection means is a concept encompassing means for injecting fuel into a cylinder provided in the compression self-ignition internal combustion engine, and refers to, for example, an injector. In this case, the injector may have a mode in which fuel is injected into the cylinder using a piezoelectric phenomenon such as a piezoelectric element (for example, a piezoelectric element).

  On the other hand, “at least the closing timing of the intake valve is variable” means that the compression self-ignition internal combustion engine is provided with a mechanism, device, system, or the like that can variably control at least the closing timing of the intake valve. Such a mechanism, apparatus, or system may be, for example, VVT or a mechanism, apparatus, or system that conforms thereto. As long as the closing timing of the intake valve is variable, for example, the opening timing of the intake valve may be variable (that is, the intake valve timing may be variable). Furthermore, the valve timing of the exhaust valve may be configured to be variable. In this case, for example, the valve timing of the exhaust valve may be variably configured by a mechanism, apparatus, or system called EX (Exhaust) -VVT. Further, not only such valve timing but also a valve lift amount may be configured to be variable.

  The “time” in the present invention belongs to the concept of time in a broad sense, but the time representing the time may not be an absolute time. For example, the time from a certain time (or timing) It may be time. Furthermore, it may be some state quantity in the compression self-ignition internal combustion engine. As such a state quantity, for example, a crank angle is suitable. In this case, the crank angle is, for example, a CA ATDC (Crank Angle After TDC: crank after top dead center) with a crank angle (ie, zero degree) at a TDC (Top Death Center) as a reference time or reference timing. Angle). For example, a position where CA ATDC is 180 degrees (−180 degrees) indicates a BDC (Bottom Death Center). Therefore, for example, “the intake valve closing timing is variable” includes that the crank angle at which the intake valve should be closed can be arbitrarily controlled.

  It should be noted that the time from TDC until reaching an arbitrary crank angle inevitably changes according to the engine speed (that is, the speed per unit time). Therefore, precisely, what is represented by the crank angle is a position concept, which is different from the time concept, but by specifying the crank angle, the result corresponds to the event on the real time axis. Even if the “time” according to the present invention is expressed based on such a crank angle or other state quantity, no problem occurs. On the other hand, the timing according to the present invention is represented by a state quantity that can comprehensively define the operation timing of each part in the compression ignition type internal combustion engine, not just the opening / closing timing of the intake valve or the exhaust valve, such as the crank angle. In this case, each part of the compression ignition type internal combustion engine can be controlled cooperatively.

  According to the control device for a compression self-ignition internal combustion engine (hereinafter referred to as “internal combustion engine” as appropriate) according to the present invention, the target ignition timing of the fuel to be injected is specified by the target ignition timing specifying means during the operation. The

  Here, the “target ignition timing” is an ignition timing as a control target. For example, in an internal combustion engine, when the ignition timing is too early (premature ignition), excessive vibration and combustion noise are likely to occur, and comfort is significantly impaired. Further, if the ignition timing is too late, misfire is likely to occur, and comfort is easily impaired accordingly. Therefore, the target ignition timing is an ignition timing that does not impair the comfort in the vehicle as described above, or that can ensure comfort relatively, and preferably the engine speed and fuel of the internal combustion engine. It is set in advance based on various state quantities such as the injection quantity.

  When preset in this way, the target ignition timing is two-dimensionally held in a non-volatile storage medium such as a ROM (Read Only Memory) provided in an ECU (Electronic Control Unit), for example. Alternatively, it may be stored in a multidimensional map in association with these state quantities. In this case, the target ignition timing specifying means may specify the target ignition timing by reading a value corresponding to the state quantity at that time from the map. The target ignition timing specifying means may specify the target ignition timing according to some algorithm or application program each time. Note that the target ignition timing may be set experimentally, empirically, or based on a simulation or the like in advance so as to ensure such comfort.

  On the other hand, the actual ignition timing, that is, the actual ignition timing is specified by the actual ignition timing specifying means. Here, “specific” means in addition to directly or indirectly detecting changes in physical, mechanical, electrical or chemical state quantities caused by the ignition of injected fuel. Estimate and predict near-future or real-time actual ignition timing by substituting various state quantities set to correlate with actual ignition timing as parameters to numerical simulation systems such as actual ignition timing calculation models Or it is a concept including the aspect to determine.

  For example, when the actual ignition timing is detected directly or indirectly as a physical phenomenon, the actual ignition timing is obtained in association with the in-cylinder pressure, crank angle, etc. obtained by means for detecting the pressure in the cylinder (for example, an in-cylinder pressure sensor). The work amount obtained from the cylinder internal volume and the specific heat ratio may be monitored, and it may be detected that the ignition has occurred when the work amount exceeds a predetermined threshold. When the actual ignition timing is estimated based on simulation, parameters such as engine speed, injection amount, water temperature, intake gas temperature, intake gas pressure, rail pressure, injection timing, intake oxygen concentration, and exhaust temperature are parameters. May be given as

  In this way, when the target ignition timing and the actual ignition timing are specified, the difference between the values that define the both is calculated by the difference calculation means. Here, the value that defines the target ignition timing or the actual ignition timing indicates, for example, values of these state quantities when these times are represented by state quantities such as a crank angle. That is, it preferably indicates the value of the crank angle.

  When the actual ignition timing coincides with the target ignition timing or deviates only to the extent that it can be regarded as coincident with each other, it is relatively easy to ensure comfort. However, if these differences are so large that they cannot be ignored, it is necessary to make the actual ignition timing asymptotic to the target ignition timing from the viewpoint of ensuring comfort. Such control of the actual ignition timing is executed by the actual ignition timing control means.

  One technique for controlling the actual ignition timing is fuel injection timing control. For example, when the fuel injection timing is controlled in the region near the top dead center, the fuel injection timing and the actual ignition timing can maintain a substantially linear relationship. If delayed, the actual ignition timing will be delayed accordingly, and the actual ignition timing can be controlled without any problem.

  Here, in particular, in a compression self-ignition internal combustion engine, there is a case where the injected fuel and the intake gas sucked from the intake system or the like are not sufficiently mixed in the period from when the fuel is injected to when it is ignited. In this case, diffusion combustion is dominant in the combustion mode in the cylinder, and soot, graphite or nitrogen oxides are relatively easily discharged. Accordingly, it is preferable that the fuel and the intake air be sufficiently mixed during the period from the injection timing to the actual ignition timing. In this way, a period in which the fuel and intake air are sufficiently mixed, that is, a premixing period is ensured, and the combustion form in the cylinder is changed from diffusion combustion to premixed compression called HCCI (Homogeneous-Charge Compression-Ignition Combustion) combustion. When controlling to self-ignition combustion, the fuel injection timing needs to be relatively advanced. However, in the region where the fuel injection timing is relatively early, the sensitivity of the injection timing to the actual ignition timing tends to be low. In such a low sensitivity region, the actual ignition timing changes linearly even if the injection timing is changed. do not do. That is, if the injection timing is advanced in order to perform HCCI combustion or the like and the premixing period is to be ensured, the actual ignition timing may be difficult to control.

  Therefore, the control device for an internal combustion engine according to the present invention solves such a problem by including a selection unit. The selection means according to the present invention is configured to be able to select at least one of the first control and the second control according to the injection timing corresponding to the actual ignition timing.

  Here, the second control refers to a process of controlling the fuel injection timing based on the difference obtained by the difference calculation means so that the actual ignition timing becomes the target ignition timing, that is, as described above. Refers to the operation of the ignition timing control means. In such injection timing control, the corresponding relationship between the difference and the actual control amount may be set to an appropriate value in advance experimentally, empirically, or based on simulation.

  On the other hand, the first control is a process of controlling the valve closing timing of the intake valve based on the calculated difference so that the actual ignition timing becomes the target ignition timing.

  The closing timing of the intake valve can affect the actual ignition timing. When the closing timing of the intake valve is relatively advanced, the compression process becomes longer, and therefore the temperature at the compression end in the cylinder tends to rise. Since the actual ignition timing is governed by the temperature of the mixture of fuel and intake gas, if the temperature at the compression end tends to rise, the temperature of the mixture tends to rise, and the actual ignition timing is relatively Easy to get faster. On the other hand, when the closing timing of the intake valve is made relatively late, the compression process becomes shorter and the amount of compressed gas also decreases, so the compression end temperature tends to decrease relatively and the actual ignition timing is relatively It tends to be late. That is, the actual ignition timing can be controlled by controlling the closing timing of the intake valve. Note that the correspondence between the control amount for controlling the closing timing of the intake valve and the difference calculated by the difference calculating means is appropriately given in advance experimentally, empirically, or based on simulation. May be.

  In order to execute the actual ignition timing control in real time, when controlling the closing timing of the intake valve, the response speed is equivalent to the response speed related to the control of the injection timing or can be regarded as equivalent to the extent that it does not cause a problem. Control needs to be performed. In view of this point, a mechanism for variably controlling the closing timing of the intake valve is preferably a mechanism having a response speed faster than the hydraulic pressure. For example, an actuator that operates electrically is preferably used.

  Note that “according to the injection timing corresponding to the actual ignition timing” means that the injection timing corresponding to the actual ignition timing is a selection index in the selection means, and typically one or more This indicates that the control is switched with the injection timing (to be precise, a value defining the injection timing) as a threshold value. It should be noted that the selection means does not necessarily need to select only one of the controls as “at least one”, and the actual ignition obtained by each of the injection timing, the magnitude of the difference, and the first control and the second control. You may select both 1st control and 2nd control suitably based on the characteristic of a time. In this case, any control may be executed dominantly.

  The actual ignition timing control means executes the control selected by the selection means in this way. Therefore, finally, the actual ignition timing is controlled efficiently and in real time, and the combustion is suitably controlled. That is, comfort is suitably maintained.

  In one aspect of the control device according to the present invention, the control device further includes reference value acquisition means for acquiring a reference value of a value that defines the injection timing corresponding to the actual ignition timing, and the selection means includes the actual ignition timing at the actual ignition timing. The at least one is selected based on a relative comparison between a value defining a corresponding injection timing and the acquired reference value.

  According to this aspect, since the selection means performs the control selection based on the relative comparison between the value defining the injection timing corresponding to the actual ignition timing and the reference value, the processing load for the control selection is relatively small. Efficient.

  The reference value may be given in advance as a fixed value, or may be set according to some state quantity in the internal combustion engine. In this case, it may be set experimentally, empirically, or based on simulation. The reference value may be determined based on some algorithm or application program each time.

  In this aspect, the value defining the injection timing corresponding to the actual ignition timing is a crank angle value at the injection timing corresponding to the actual ignition timing in the compression ignition type internal combustion engine, and the selection means The first control may be selected when the crank angle value is smaller than the reference value, and the second control may be selected when the crank angle value is larger than the reference value.

  When the injection timing is represented by the crank angle, as described above, cooperative control in the internal combustion engine is possible, which is preferable. When the injection timing is defined by the crank angle, the reference value is necessarily defined by the crank angle value. At this time, the crank angle may be expressed with any crank position as a reference, but preferably TDC is used as a reference as described above. Even when the TDC is used as a reference, the reference value and the value specifying the injection timing differ depending on whether the deviation is specified in the positive or negative direction, but the specified time is the same and the problem arises. Absent.

  Here, considering that the fuel injection timing is generally defined in the process of the piston moving from BDC to TDC (generally coincides with the compression process), “when the crank angle value is smaller than the reference value” Inevitably indicates that the injection timing is on the BDC side (that is, the advance side) with respect to the timing defined by the reference value, and “when the crank angle value is larger than the reference value” It represents that the time is on the TDC side (that is, the retard side) with respect to the time defined by the reference value. That is, in this case, the actual ignition timing is controlled by the injection timing when the injection timing corresponding to the actual ignition timing is relatively close to TDC, and by the closing timing of the intake valve when relatively far from TDC. Will be. If the injection timing exceeds a crank position that is more advanced than TDC (that is, the crank angle), the sensitivity to the actual ignition timing is often extremely reduced. When the crank position corresponding to such a threshold value can be set, the actual ignition timing can be efficiently controlled by executing one of the controls.

  In addition, “when smaller than the reference value” and “when larger than the reference value” respectively mean “when it is below the reference value” and “when it is above the reference value” depending on the setting mode of the reference value. It is a concept that can be mutually replaced.

  In another aspect of the control device according to the present invention including reference value acquisition means, the control apparatus further includes storage means for storing a plurality of reference values in association with predetermined state quantities in the compression ignition type internal combustion engine. The reference value acquisition unit acquires the reference value by selecting a reference value corresponding to the predetermined state quantity at the present time from the plurality of stored reference values.

  According to this aspect, since a plurality of reference values are stored in the storage unit, it is possible to easily obtain the reference values. The predetermined state quantity corresponding to the reference value may be any state quantity of the internal combustion engine as long as the reference value can be suitably set. For example, the engine speed may be used. Note that “stored in association” means that a reference value is stored in advance as a one-dimensional, two-dimensional, or multidimensional map.

  In the control device according to the present invention including a storage unit, the reference value acquisition unit further corrects the selected reference value based on another state quantity different from the predetermined state quantity. A reference value may be acquired.

  Considering that the control selection is governed by the mode of setting the reference value, it is desirable that the reference value is appropriately corrected in accordance with the state quantity in the internal combustion engine each time. In this case, since the reference value is corrected by another state quantity different from the state quantity used to obtain the reference value, it becomes possible to set the reference value more finely, and as a result, the selection means This is preferable because the selection of control by is effectively executed.

  In another aspect of the control apparatus according to the present invention including a reference value acquisition unit, the reference value acquisition unit calculates the reference value based on a predetermined state quantity in the compression ignition type internal combustion engine. Get the reference value.

  In addition to being stored in advance as a fixed value, or in addition to appropriately correcting the value stored as a fixed value, the reference value may be obtained numerically each time. In this case, for example, the cylinder volume at the start of combustion is calculated based on the gas temperature in the cylinder at which the combustion is started, the gas temperature at the start of compression, and the cylinder volume at the time of closing the intake valve, and the cylinder volume is calculated. The reference value may be obtained from

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment>
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate.

<First Embodiment>
<Configuration of Embodiment>
First, the configuration of the engine system according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of the engine system 10.

  In FIG. 1, the engine system 10 includes an ECU 100 and an engine 200.

  The ECU 100 includes an unillustrated CPU, ROM, RAM (Random Access Memory), and the like, and is an electronic control unit that controls the overall operation of the engine 200. The "control device for a compression self-ignition internal combustion engine" according to the present invention. It can be configured to function as an example. In the ROM, for example, a control program for the ECU 100 to control the ignition timing of fuel in the engine 200, various maps to be described later, and the like are stored in advance. The RAM is configured to temporarily store various data generated in the process of controlling the ignition timing by the ECU 100 and output values of various sensors described later.

  The engine 200 is a diesel engine for a vehicle that is an example of a “compression self-ignition internal combustion engine” according to the present invention. In each of the plurality of cylinders 202 accommodated in the cylinder block 201, the fuel injected by the injector 209 is automatically generated. It is configured to be able to ignite and explode, and to convert a reciprocating motion of a piston (not shown) generated according to the explosive force into a rotating motion of a crankshaft (not shown) via a connection rod (not shown). ing. Below, the principal part structure of the engine 200 is demonstrated with the operation | movement. The plurality of cylinders 202 have the same configuration, and in FIG. 1, the reference numerals of the overlapping portions are partially omitted in order to prevent the drawing from becoming complicated.

  When the fuel in the cylinder 202 is burned, the air sucked from the outside is supplied to the cylinder 202 via the intake manifold 203. An air flow meter 204 is disposed in the intake manifold 203. The air flow meter 204 has a form called a hot wire type, and is configured to be able to directly measure the mass flow rate of inhaled air. The intake manifold 203 further includes an intake air temperature sensor 205 for detecting the temperature of intake air (intake air temperature), an intake pressure sensor 206 for detecting the pressure of intake air (intake air pressure), and the oxygen concentration of intake air (intake air). O2 sensors 220 for detecting (oxygen concentration) are respectively installed. The air flow meter 204, the intake air temperature sensor 205, the intake pressure sensor 206, and the O2 sensor 220 are electrically connected to the ECU 100, respectively.

  The communication state between the cylinder 202 and the intake manifold 203 is controlled according to the opening / closing of the intake valve 207. The opening and closing of the intake valve 207 is controlled by the cam and the operation of the camshaft that are linked to the operation of the crankshaft. The engine 200 according to this embodiment is further opened and closed by an electrically driven actuator 208. It is the structure which can control a time variably. The actuator 208 is electrically connected to the ECU 100, and therefore the opening / closing timing of the intake valve can be controlled by the ECU 100.

  Fuel is supplied to the injector 209 from a fuel tank (not shown) via the common rail 210 and the branch pipe 211. The injector 209 directly injects the supplied fuel into the cylinder 202 according to the control of the ECU 100. Is configured to be possible. The common rail 210 is configured to supply high-pressure fuel to the injector 209 in order to stably supply fuel into the high-temperature and high-pressure cylinder. The rail pressure is the rail pressure sensor 212. Is detected and output to the ECU 100.

  Inside the cylinder 202, the fuel injected by the injector 209 and the sucked air are mixed and compressed as a mixed gas, and further mixed by the mixed gas reaching the combustion temperature in the process of the compression. Gas burns. The cylinder 202 is provided with an in-cylinder pressure sensor 213 that is electrically connected to the ECU 100 so that the pressure in the cylinder 202 can be detected. The burned mixed gas becomes exhaust gas, passes through an exhaust valve 216 that opens and closes in conjunction with opening and closing of the intake valve 207, and is exhausted through an exhaust manifold 217. At this time, the temperature of the exhaust gas is detected by an exhaust temperature sensor 218 that is electrically connected to the ECU 100. Further, a catalyst 219 is installed in the exhaust manifold 217 to purify the exhaust gas.

  In the vicinity of the crankshaft, a crank position sensor 214 that detects the rotational position (ie, crank angle) of the crankshaft is installed. The crank position sensor 214 is electrically connected to the ECU 100, and the ECU 100 determines the position of the piston in the cylinder 202 and the engine speed of the engine 200 based on the rotation state of the crankshaft obtained from the crank position sensor 214. It is configured to be able to obtain. Cooling water for cooling the engine 200 circulates in a water jacket (not shown) in the cylinder block 201, and the temperature is detected by a cooling water temperature sensor 215 electrically connected to the ECU 100. It has a configuration.

<Operation of Embodiment>
<Control of ignition timing>
In the engine 200, fuel is self-ignited by being compressed in the cylinder, but the ignition timing can be controlled in real time from the viewpoint of ensuring the comfort of the vehicle equipped with the engine system 10. Is desirable. Normally, the ECU 100 controls the fuel ignition timing by controlling the fuel injection timing. Here, the ignition timing control based on the injection timing will be described with reference to FIG. FIG. 2 is a correlation diagram between the fuel injection timing and the ignition timing.

  In FIG. 2, the vertical axis and the horizontal axis represent the ignition timing and the injection timing, respectively. Both the ignition timing and the injection timing are represented by a crank angle after top dead center (CA ATDC). The crank angle after the top dead center is a deviation of the crank angle with respect to the top dead center (TDC). For example, “−20” on the horizontal axis in the figure is advanced by 20 degrees from the top dead center. Represents the crank position.

  The injection timing is normally set to a crank angle belonging to the illustrated area A including the top dead center. In region A, the sensitivity of the ignition timing with respect to the injection timing (that is, the inclination of the ignition timing with respect to the injection timing) is relatively large, and the fuel ignites after a substantially constant delay from the injection timing. Therefore, in this region A, the ignition timing control by the injection timing is relatively easy.

  On the other hand, in the illustrated region B where the advance angle from the top dead center is relatively large, the sensitivity of the ignition timing with respect to the injection timing is small, and it is difficult to control the ignition timing based on the injection timing. In such a case, premature ignition or misfire may occur, and it is difficult to ensure comfort. However, from the viewpoint of pursuing environmental performance, it is preferable to premix the fuel as much as possible in the cylinder to promote HCCI combustion. In order to secure the premixing period for this purpose, the injection timing needs to be relatively advanced as shown in the region B in the figure. In order to suitably combine such contradictory events, the ignition timing control process is executed by the ECU 100 in the engine system 10 according to the present embodiment. At this time, the ECU 100 executes an ignition timing control process according to a control program stored in the ROM. Here, with reference to FIG. 3, the details of the ignition timing control process will be described as the operation of the present embodiment. FIG. 3 is a flowchart of the ignition timing control process.

  In FIG. 3, first, the engine speed Ne of the engine 200 is acquired (step A10). The engine speed Ne can be calculated by the ECU 100 itself based on the sensor output from the crank position sensor 214. The acquired engine speed Ne is temporarily stored in the RAM.

  Next, the ECU 100 acquires the fuel injection amount Q (step A11). The ECU 100 controls the injector 209 to the upper level, and the ECU 100 holds the injection amount Q as a control value. In obtaining the injection amount Q, the ECU 100 refers to an injection amount map in which the injection amount Q is associated with the engine speed Ne and the accelerator pedal opening. Such an injection amount map is stored in advance in the ROM. The accelerator pedal opening is acquired from an accelerator position sensor (not shown) that detects the amount of depression of an accelerator pedal (not shown in FIG. 1). The value of the injection amount Q is also temporarily stored in the RAM.

  When the engine speed Ne and the injection amount Q are acquired, the ECU 100 acquires the target ignition timing CAa based on these values (step A12). In the present embodiment, the timing at which the ECU 100 controls the operation of the engine 200 is defined by the crank angle, and therefore the target ignition timing CAa is also acquired as the value of the crank angle. The crank angle in this embodiment is assumed to be the crank angle after top dead center (CA ATDC).

  The target ignition timing Ta is stored in advance as a control map in the ROM so as to be associated with the fuel injection amount Q and the engine speed Ne. In step A12, the ECU 100 obtains the target ignition timing CAa by reading the corresponding value from the control map stored in the ROM based on the fuel injection amount Q and the engine speed Ne buffered in the RAM. Note that the value of the target ignition timing CAa is temporarily buffered in the RAM.

  When the target ignition timing CAa is acquired, the ECU 100, based on the output values of the various sensors shown in FIG. 1, the cooling water temperature Tw, the intake air temperature Ti, the intake pressure Pi, the rail pressure Pr, the injection timing CAi, and the intake oxygen concentration Do. And the exhaust temperature Te is acquired (step A13). Note that the ECU 100 itself holds the injection timing CAi as a control value. Each of these values is temporarily buffered in RAM.

  The ECU 100 acquires the actual fuel ignition timing CAr (step A14). The actual ignition timing CAr is calculated by the ECU 100 performing a numerical operation based on an actual ignition timing calculation model stored in advance in the ROM. At this time, each value obtained in step A13, the engine speed Ne, and the injection amount Q are used as parameters. By acquiring the actual ignition timing numerically in this way, the actual ignition timing CAr can be acquired before the fuel actually ignites. Therefore, the real-time property of ignition timing control is suitably secured. The actual ignition timing CAr may be acquired based on, for example, a pressure change in the cylinder that is detected by the in-cylinder pressure sensor 213 and that occurs as an actual phenomenon during combustion.

  When the actual ignition timing CAr is calculated, the ECU 100 calculates a difference ΔCA between the target ignition timing CAa and the actual ignition timing CAr (step A15). The difference ΔCA is a target deviation that defines a control amount when the actual ignition timing CAr is controlled later.

  When the difference ΔCA is calculated, the ECU 100 acquires the reference value a (step A16). Here, the reference value a will be described with reference to FIG.

  In FIG. 2, the reference value a is a crank angle that defines the boundary between the region A and the region B, and a value larger than the reference value a (that is, a value on the retard side) is in the region A than the reference value a. Also, a smaller value (that is, a value on the advance side) is determined to belong to the region B. Even if the characteristics of the engine 200 are not clearly divided into the regions A and B as shown in the figure, the reference value a is not necessarily clearly defined as long as the macroscopic or qualitative concept is secured. It does not have to be a value that defines the boundary between these two regions.

  Returning to FIG. 3, the reference value a is stored in the ROM in advance as a reference value map associated with the engine speed Ne, and the ECU 100 is a value corresponding to the value of the engine speed Ne buffered in the RAM. By reading out from the map, the reference value a can be easily obtained.

  When the reference value a is acquired, the ECU 100 determines whether or not the injection timing CAi buffered in the RAM is less than the reference value a (step A17). If the injection timing CAi is greater than or equal to the reference value a (step A17: NO), that is, if the injection timing CAi is the reference value a or a value that is retarded from the reference value a, the injection timing is It belongs to the area A in FIG. 2, and the sensitivity of the injection timing to the ignition timing is good. Therefore, as already described, control of the actual ignition timing CAr based on the injection timing CAi (that is, an example of “second control” according to the present invention) is executed (step A19). At this time, the control amount (crank angle) of the injection timing CAi is determined based on the difference ΔCA calculated in step A15. The control amount of the injection timing CAi with respect to the difference ΔCA is stored in advance in the ROM as a control map.

  On the other hand, when the injection timing CAi is less than the reference value a (step A17: YES), that is, when the injection timing CAi is a value on the advance side of the reference value a, the injection is performed as described above. Since the timing belongs to the region B (see FIG. 2) where the sensitivity to the ignition timing is low, the ECU 100 controls the actual ignition timing CAr based on the closing timing CAv of the intake valve 207 (that is, the “first control” according to the present invention). Example) is executed (step A18).

  Here, the ignition timing control by the intake valve closing timing will be described with reference to FIGS. FIG. 4 is a correlation diagram between the intake valve closing timing and the cylinder compression end temperature, and FIG. 5 is a correlation diagram between the intake valve closing timing and the ignition timing.

  In FIG. 4, the vertical axis and the horizontal axis represent the compression end temperature and the intake valve closing timing, respectively. As shown in the figure, the compression end temperature tends to increase as the intake valve closing timing is advanced (leftward in the figure), and the compression end is increased as the intake valve closing timing is delayed (rightward in the figure). The temperature tends to decrease. That is, as the valve closing timing of the intake valve is on the advance side with respect to the top dead center, the compressible volume (compression white) and the amount of compressed gas increase, so that the compression end temperature rises.

  The compression end temperature greatly affects the ignition timing. This will be described with reference to FIG. In FIG. 5, the vertical axis and the horizontal axis represent the ignition timing and the intake valve closing timing, respectively. As shown in the figure, the ignition timing becomes earlier (that is, shifts to the advance side) as the intake valve closing timing goes toward the advance side, and the ignition timing becomes later as the intake valve closing timing goes toward the retard side. (That is, shift to the retard side). That is, the higher the compression end temperature, the faster the fuel ignites. The ignition timing of the fuel is defined by the timing when the fuel reaches the ignition temperature. When fuel is injected, the temperature rises while receiving heat from the compressed air. Therefore, the higher the compression end temperature, the faster the temperature of the mixed gas increases and the earlier the time when the fuel reaches the ignition point. Therefore, it is possible to control the ignition timing satisfactorily by controlling the intake valve closing timing. Returning to FIG. 3, the control amount (ie, crank angle) of the closing timing of the intake valve 207 is determined based on the difference ΔCA calculated in step A15. The control amount of the intake valve closing timing CAv with respect to the difference ΔCA is stored in advance in the ROM as a control map.

  When the actual ignition timing CAr is controlled in step A18 or step A19, the process returns to step A10 and a series of processes are repeated. As described above, according to the ignition timing control process according to the present embodiment, it is possible to suitably control the ignition timing by properly using the ignition timing control based on the injection timing and the ignition timing control based on the intake valve closing timing. It is possible to maintain comfort.

Second Embodiment
The mode of acquiring the reference value a that defines whether the actual ignition timing CAr is controlled by the injection timing CAi or the intake valve closing timing CAv is not limited to that of the first embodiment. Here, the ignition timing control process according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a flowchart of the ignition timing control process. In the figure, the same reference numerals are assigned to the same parts as those in FIG. 3, and the description thereof is omitted.

  In step A16 in FIG. 6, when the reference value a is obtained by map matching based on the engine speed Ne, the ECU 100 further obtains the intake valve closing timing CAv (step B10). Here, the intake valve closing timing CAv is held as a control amount by the ECU 100 based on the initial value based on the crankshaft, the cam, the camshaft, and the like, the control amount of the actuator 208, and the like, and can be easily obtained. .

  When the intake valve closing timing CAv is acquired, the ECU 100 corrects the reference value a acquired in step A16 based on the intake valve closing timing CAv, the buffered coolant temperature Tw, and the intake air temperature Ti (step A16). B11). Here, the ROM stores in advance a correction map in which the intake valve closing timing CAv, the cooling water temperature Tw, the intake air temperature Ti, and the correction amount are associated with each other, and the ECU 100 corresponds to these maps. The correction amount is read and the reference value a is corrected. In addition, the aspect of correction | amendment is not limited to this, You may take various forms. The following steps are executed based on the reference value a corrected in this way.

  According to the present embodiment, the reference value a can be determined more precisely, and the actual ignition timing CAr can be controlled more precisely. Therefore, comfort can be more suitably maintained.

<Third Embodiment>
The reference value “a” can be acquired under another mode. Here, the ignition timing control process according to the third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a flowchart of the ignition timing control process. In the figure, the same reference numerals are assigned to the same parts as in FIG.

  When the intake valve closing timing CAv is acquired in step B10 in FIG. 7, the ECU 100 further acquires the intake air amount Wi from the air flow meter 204 (step C10). When the intake air amount Wi is acquired, the ECU 100 calculates a reference volume Vb (step C11).

  Here, the reference volume Vb is the cylinder volume when the fuel combustion reaction starts in the cylinder 202 (that is, the volume of the space surrounded by the cylinder inner wall surface and the piston upper surface), and is defined by the following equation (1). Is done. Note that κ is a specific heat ratio.

Vb = volume when intake valve is closed × (gas temperature at the start of compression / reference temperature) ^{(1 / (κ−1))} (1)
Here, the intake valve closing volume is a cylinder volume when the intake valve 207 is closed. The ROM stores in advance a map in which the crank angle and the cylinder volume are associated with each other. If the crank angle is acquired, the corresponding cylinder volume can be easily acquired. In the present embodiment, since the intake valve closing timing is defined by the value of the crank angle, the intake valve closing volume is easily obtained. The reference temperature is a temperature at which a fuel combustion reaction starts, and is a fixed value if the type of fuel does not change. Here, it is assumed that the value is a fixed value. On the other hand, the gas temperature at the start of compression is the gas temperature at the start of compression in the cylinder 202, and is calculated based on the intake air temperature Ti, the cooling water temperature Tw, and the intake air amount Wi.

  When the reference volume Vb is calculated by the calculation based on the above formula (1), the ECU 100 acquires the reference value a based on the reference volume Vb (step C12). The reference value a is a crank angle value corresponding to the reference volume Vb, and can be easily obtained from a map in which the cylinder volume and the crank angle are associated with each other as described above.

  The region on the retard side from the reference value a is a region where the gas temperature in the cylinder is sufficiently high, and the region where the fuel injection timing CAi affects the actual ignition timing CAr relatively linearly. That is, it is equivalent to a region corresponding to the region A in FIG. On the other hand, the region on the more advanced side than the reference value a is a region where the gas temperature in the cylinder is relatively low, and the region where the fuel injection timing CAi hardly affects the actual ignition timing CAr. That is, the region corresponds to the region B in FIG. Therefore, the actual ignition timing CAr is preferably determined in the same manner as in the first and second embodiments described above, depending on whether or not the current injection timing CAi is the timing (crank angle) corresponding to the reference volume Vb. It becomes possible to control to.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and the compression ignition type with such a change. A control device for an internal combustion engine is also included in the technical scope of the present invention.

It is a mimetic diagram of an engine system concerning a 1st embodiment of the present invention. FIG. 2 is a correlation diagram between injection timing and ignition timing in the engine system of FIG. 1. It is a flowchart of the ignition timing control process which ECU performs in the engine system of FIG. FIG. 5 is a correlation diagram between the closing timing of the intake valve and the compression end temperature. It is a correlation diagram of the valve closing timing and the ignition timing of the intake valve. It is a flowchart of the ignition timing control process which concerns on 2nd Embodiment of this invention. It is a flowchart of the ignition timing control process which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 207 ... Intake valve, 208 ... Actuator, 209 ... Injector, 214 ... Crank position sensor

Claims (6)

A control device for a compression self-ignition internal combustion engine for controlling a compression self-ignition internal combustion engine comprising injection means for injecting fuel and at least the valve closing timing of the intake valve being variable,
Target ignition timing specifying means for specifying the target ignition timing of the injected fuel;
An actual ignition timing specifying means for specifying an actual ignition timing of the injected fuel;
Difference calculating means for calculating a difference between a value defining the target ignition timing and a value defining the actual ignition timing;
In accordance with the fuel injection timing corresponding to the actual ignition timing, (i) a first control that controls the valve closing timing of the intake valve based on the difference so that the actual ignition timing becomes the target ignition timing And (ii) selection means for selecting at least one of second controls for controlling the fuel injection timing based on the difference so that the actual ignition timing becomes the target ignition timing;
A control device for a compression self-ignition internal combustion engine, comprising: actual ignition timing control means for controlling the actual ignition timing by executing at least one of the selected. Further comprising reference value acquisition means for acquiring a reference value of a value defining the injection timing corresponding to the actual ignition timing;
2. The compression according to claim 1, wherein the selection unit selects the at least one based on a relative comparison between a value defining an injection timing corresponding to the actual ignition timing and the acquired reference value. Control device for self-igniting internal combustion engine. The value defining the injection timing corresponding to the actual ignition timing is a value of the crank angle at the injection timing corresponding to the actual ignition timing in the compression ignition type internal combustion engine,
The selection means selects the first control when the crank angle value is smaller than the reference value, and selects the second control when the crank angle value is larger than the reference value. The control device for a compression self-ignition internal combustion engine according to claim 2, Storage means for storing a plurality of the reference values in association with predetermined state quantities in the compression ignition type internal combustion engine,
The reference value acquisition unit acquires the reference value by selecting a reference value corresponding to the predetermined state quantity at the present time from the plurality of stored reference values. 3. A control device for a compression self-ignition internal combustion engine according to 3. The reference value acquisition unit further acquires the reference value by correcting the selected reference value based on another state quantity different from the predetermined state quantity. Control device for a compression self-ignition internal combustion engine. The compression according to claim 2 or 3, wherein the reference value acquisition means acquires the reference value by calculating the reference value based on a predetermined state quantity in the compression self-ignition internal combustion engine. Control device for self-igniting internal combustion engine.

Images