JP6225969B2 - Control device and control method for internal combustion engine with supercharger - Google Patents

Description

  The present invention relates to a control device and a control method for an internal combustion engine with a supercharger, and more particularly, to a control device and a control method for an internal combustion engine with a supercharger that execute control corresponding to pre-ignition (self-ignition before ignition). .

As a conventional technique, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 11-36965), an internal combustion engine having a function of detecting the occurrence of pre-ignition based on the temperature (wall surface temperature) in the combustion chamber. Control devices are known.
The applicant has recognized the following documents including the above-mentioned documents as related to the present invention.

JP 11-36965 A

  In the above-described prior art, the occurrence of pre-ignition can be detected based on the wall surface temperature of the combustion chamber, but this state can be effectively eliminated even if the wall surface temperature is likely to induce pre-ignition. There is a problem that can not be. Particularly in an engine with a supercharger, pre-ignition is likely to occur in a low-rotation and high-load region, and therefore effective control for avoiding pre-ignition is required. That is, in the prior art, there is room for improvement in control for optimizing the wall temperature of the combustion chamber so that preignition does not occur.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to appropriately control the in-cylinder temperature and suppress the occurrence of pre-ignition before pre-ignition actually occurs. Another object of the present invention is to provide a control device and a control method for an internal combustion engine with a supercharger that can be used.

According to a first aspect of the present invention, there is provided a control device applied to an internal combustion engine having a supercharger including a fuel injection valve, a spark plug, and a supercharger, wherein a cylinder wall temperature of the internal combustion engine or a parameter corresponding to the cylinder wall temperature is set as a wall. Wall temperature parameter acquisition means for acquiring as a temperature parameter, and pre-ignition suppression means for executing pre-ignition suppression control for reducing the in-cylinder temperature in order to suppress pre-ignition that occurs before ignition by the spark plug. The pre-ignition suppression means is operating in a predetermined low-rotation and high-load region between the start of the internal combustion engine and the completion of warm-up , and the occurrence frequency of the pre-ignition and the wall temperature the wall temperature parameter smaller than the temperature lower limit value of the temperature region in which the frequency in relation to the parameter is less than the allowable limit If, and executes the pre-ignition suppression control.

  According to the second invention, the preignition suppression control lowers the in-cylinder temperature by performing an increase correction of the fuel injection amount by the fuel injection valve.

According to a third invention, the internal combustion engine with a supercharger includes an intake valve and an exhaust valve,
The pre-ignition suppression control reduces the in-cylinder temperature by controlling the valve timing of the intake valve or the exhaust valve.

According to a fourth aspect of the present invention, there is provided a control method applied to an internal combustion engine with a supercharger including a fuel injection valve, a spark plug, and a supercharger, wherein a cylinder wall temperature of the internal combustion engine or a parameter corresponding to the cylinder wall temperature is set as a wall. Acquired as a temperature parameter, the engine is operating in a predetermined low rotation high load region from the start of the internal combustion engine to the completion of warm-up , and the occurrence frequency of pre-ignition and the wall temperature parameter If the said wall temperature parameters than the temperature lower limit value of the temperature region where the frequency is less than the allowable limit small again in relation, in-cylinder temperature to suppress preignition ignition occurs before ignition by the spark plug Preignition suppression control that reduces the

  According to a fifth aspect of the invention, the preignition suppression control reduces the in-cylinder temperature by performing an increase correction of the fuel injection amount by the fuel injection valve.

According to a first aspect of the present invention, in a state in which performs operation at a predetermined low rotation and high load region during a period from starting the internal combustion engine until warm-up is completed, when the wall temperature parameter is low, The pre-ignition suppression control can reduce the in-cylinder temperature and suppress the occurrence of pre-ignition.

  According to the second invention, the pre-ignition suppression control can reduce the in-cylinder temperature by performing an increase correction of the fuel injection amount, and can suppress the occurrence of pre-ignition.

  According to the third invention, the pre-ignition suppression control can reduce the in-cylinder temperature by controlling the valve timing of the intake valve or the exhaust valve, thereby suppressing the occurrence of pre-ignition.

According to a fourth aspect of the present invention, in a state in which performs operation at a predetermined low rotation and high load region during a period from starting the internal combustion engine until warm-up is completed, when the wall temperature parameter is low, The pre-ignition suppression control can reduce the in-cylinder temperature and suppress the occurrence of pre-ignition.

  According to the fifth aspect of the present invention, the pre-ignition suppression control can reduce the in-cylinder temperature by performing an increase correction of the fuel injection amount and suppress the occurrence of pre-ignition.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is explanatory drawing which shows a pre-ignition frequent operation area | region. It is a characteristic diagram which shows the in-cylinder pressure when preignition occurs. It is a characteristic diagram which shows the relationship between the generation | occurrence | production frequency of pre-ignition in a pre-ignition frequent operation area | region, and cylinder wall temperature. It is a characteristic diagram which shows the data map which data-ized the relationship between cylinder wall temperature and engine water temperature. It is a characteristic diagram which shows a mode that the raise speed | rate of cylinder wall temperature changes according to the amount of cooling water of an engine in a low temperature area | region. It is explanatory drawing which shows the execution area | region of preignition suppression control. In Embodiment 1 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 2 of this invention, it is a characteristic diagram which shows the case where a preignition suppression temperature area | region is shifted to the high temperature side by the change of a fuel property, etc. In Embodiment 2 of this invention, it is a characteristic diagram which shows the case where a preignition suppression temperature area | region is shifted to the low temperature side by the change of a fuel property, etc. FIG. In Embodiment 2 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 3 of this invention, it is a characteristic diagram which shows the case where a preignition suppression temperature area | region is shifted to the low temperature side by the change of a fuel property, etc. In Embodiment 4 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 5 of the present invention, the cylinder wall temperature t rises by starting the engine from a state where the cylinder wall temperature t is in the low temperature region (t <temperature upper limit value t1) and pre-ignition is likely to occur. It is explanatory drawing which shows a mode that it goes. It is a characteristic diagram for setting delay time ta of preignition suppression control from cylinder wall temperature t at the time of rush. In Embodiment 5 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 6 of this invention, it is explanatory drawing which shows the correction control which correct | amends the relationship between the cylinder wall temperature t at the time of rushing, and the delay time ta of preignition suppression control.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 and 8. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system according to the present embodiment includes an engine 10 as a multi-cylinder internal combustion engine. In FIG. 1, only one cylinder of the engine 10 is illustrated. Further, the present invention is applied to an engine having an arbitrary number of cylinders including a single cylinder. In each cylinder of the engine 10, a combustion chamber 14 is defined by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine. Further, the engine 10 includes an intake passage 18 that sucks intake air into the combustion chamber 14 (cylinder) of each cylinder, and an exhaust passage 20 that exhausts exhaust gas from each cylinder.

  The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the amount of intake air based on the accelerator opening and the like, and an intercooler 24 that cools the intake air. The exhaust passage 20 is provided with an exhaust purification catalyst 26 such as a three-way catalyst for purifying exhaust gas. Each cylinder has a fuel injection valve 28 for injecting fuel into the intake port, an ignition plug 30 for igniting the air-fuel mixture in the cylinder, an intake valve 32 for opening and closing the intake port relative to the cylinder, and an exhaust port. And an exhaust valve 34 that opens and closes the inside of the cylinder. Further, the engine 10 includes a known turbocharger 36 that supercharges intake air using exhaust pressure. The turbocharger 36 includes a turbine 36 a provided in the exhaust passage 20 on the upstream side of the exhaust purification catalyst 26 and a compressor 36 b provided in the intake passage 18. When the turbocharger 36 is operated, the turbine 36a receives the exhaust pressure and drives the compressor 36b, whereby the compressor 36b supercharges the intake air.

  The system of the present embodiment also includes a cooling water amount variable mechanism 38 that adjusts the amount of engine cooling water (cooling water amount) that circulates between the engine 10 and a radiator (not shown). The cooling water amount variable mechanism 38 has a known mechanism as described in, for example, Japanese Patent Application Laid-Open No. 2005-240723, Japanese Patent Application Laid-Open No. 11-13512, and the like, and is a variable displacement pump disposed in the engine cooling water channel. And a switching valve for switching the flow path of the cooling water. The cooling water amount variable mechanism 38 is controlled by an ECU 50 to be described later, and constitutes a cylinder wall temperature variable means capable of changing the wall surface temperature (cylinder wall temperature) of the combustion chamber 14 by increasing or decreasing the amount of engine cooling water. Yes.

  Next, an engine control system will be described. The system according to the present embodiment includes a sensor system including sensors 40 to 46 and an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. First, the sensor system will be described. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount of the engine. The water temperature sensor 44 detects the temperature of the engine cooling water (engine water temperature tw). The engine water temperature tw is used as a wall temperature parameter corresponding to the cylinder wall temperature t as will be described later, and the water temperature sensor 44 constitutes a wall temperature parameter acquisition unit of the present embodiment.

  The in-cylinder pressure sensor 46 detects the in-cylinder pressure and is provided in each cylinder. The in-cylinder pressure sensor 46 constitutes a pre-ignition detection unit that detects the occurrence of pre-ignition as will be described later. In addition to this, the sensor system includes various sensors (air-fuel ratio sensor for detecting the exhaust air-fuel ratio, accelerator sensor for detecting the accelerator operation amount of the driver, etc.) necessary for engine and vehicle control. . These sensors are connected to the input side of the ECU 50. On the other hand, on the output side of the ECU 50, various actuators including a throttle valve 22, a fuel injection valve 28, a spark plug 30, a cooling water amount variable mechanism 38, and the like are connected.

  The ECU 50 is configured by an arithmetic processing device including a storage circuit such as a ROM, a RAM, and a nonvolatile memory and an input / output port. Then, the ECU 50 controls the operating state by driving each actuator while detecting engine operation information by the sensor system. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of the crank angle sensor 40, and the intake air amount is calculated based on the output of the air flow sensor 42. Further, the engine load state (load factor) is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 28 and the spark plug 30 are driven. Thereby, the air-fuel mixture is combusted in the cylinder, and the engine is operated.

[Features of Embodiment 1]
First, with reference to FIGS. 2 and 3, for example, a pre-ignition tendency in an engine with a supercharger will be described. FIG. 2 is an explanatory diagram showing the pre-ignition frequent operation region A, and FIG. 3 is a characteristic diagram showing in-cylinder pressure when pre-ignition occurs. In an engine with a supercharger, as shown in FIG. 2, for example, pre-ignition is likely to occur in a low rotation and high load region in an operation region determined according to the engine speed and torque, for example. When pre-ignition occurs, as shown in FIG. 3, the maximum in-cylinder pressure (Pmax) and the in-cylinder temperature become abnormally high as compared with the case of normal combustion, so engine parts are easily affected. The low rotation high load region is an operation region in which, for example, the torque is 60 to 70% or more of the maximum output, and the engine speed is 40 to 50% or less of the maximum rotation number. In the present embodiment, the following control will be described by taking a low rotation and high load region in an engine with a supercharger as an example of the pre-ignition frequent operation region A.

  FIG. 4 is a characteristic diagram showing a relationship between the occurrence frequency of pre-ignition in the pre-ignition frequent operation region A and the cylinder wall temperature. As shown in this figure, according to the applicant of the present invention, the occurrence frequency of pre-ignition (number of occurrences per unit time) is such that the cylinder wall temperature t is between a predetermined temperature lower limit value t1 and a temperature upper limit value t2. It was found to be minimal when it was within the range. In the following description, the temperature region (t1 ≦ t ≦ t2) of the cylinder wall temperature at which the occurrence frequency of pre-ignition is minimized is expressed as “pre-ignition suppression temperature region”. The pre-ignition suppression temperature region is considered to be generated for the following reason.

  First, during the operation of the engine, the oil left by the piston reciprocating in the cylinder tends to accumulate in the piston clevis. As a result, when the oil dilution ratio (the ratio at which the injected fuel is mixed with the oil) increases, the viscosity of the oil decreases and the oil droplets are easily scattered in the cylinder, and the scattered oil droplets become a fire type and become pre-ignition. Is generated. Here, in the low temperature region where the cylinder wall temperature t is lower than the temperature lower limit value t1 (t <t1), the injected fuel is basically difficult to evaporate, so the oil dilution rate tends to increase and pre-ignition occurs. easy. However, if the cylinder wall temperature t rises from this state, the fuel easily evaporates and the oil dilution rate decreases, so that the oil droplets are less likely to fly, the fire type is reduced, and pre-ignition is less likely to occur. That is, in the low temperature region, the pre-ignition occurrence frequency decreases as the cylinder wall temperature t increases toward the pre-ignition suppression temperature region.

  On the other hand, in the high temperature region where the cylinder wall temperature t is higher than the temperature upper limit value t2 (t> t2), if the cylinder wall temperature rises, the cylinder temperature rises accordingly, so preignition occurs due to ignition due to high temperature. It becomes easy to do. That is, in the high temperature region, the pre-ignition occurrence frequency increases as the cylinder wall temperature t rises from the pre-ignition suppression temperature region toward the high temperature side. Thus, the pre-ignition suppression temperature region has a characteristic that the pre-ignition occurrence frequency is lower than the surrounding temperature region, and is an optimal temperature region for suppressing pre-ignition. Therefore, in the present embodiment, the following cylinder wall temperature control is executed. The specific ranges (temperature lower limit value t1 and temperature upper limit value t2) of the pre-ignition suppression temperature region are obtained by experiments or the like.

(Cylinder wall temperature control)
In the cylinder wall temperature control, when the region where the engine is actually operated (hereinafter referred to as the actual operation region) is in the pre-ignition frequent operation region A, the cooling of the engine is performed using the cooling water amount variable mechanism 38. The amount of water is changed, and control is performed so that the cylinder wall temperature t falls within the pre-ignition suppression temperature region (t1 ≦ t ≦ t2). More specifically, first, the ECU 50 constituting the pre-ignition temperature region storage means of the present embodiment has data defining the pre-ignition suppression temperature region (characteristic line data shown in FIG. 4 or at least the temperature lower limit value). t1 and temperature upper limit value t2) are stored in advance. The ECU 50 also stores in advance a data map (see FIG. 5) in which the relationship between the cylinder wall temperature t and the engine water temperature tw is converted into data. The ECU 50 calculates the cylinder wall temperature t from the engine water temperature tw based on this data map. For example, when the cylinder wall temperature t is lower than the temperature lower limit value t1, the ECU 50 controls the cooling water amount variable mechanism 38 to control the engine. The amount of cooling water is reduced from the normal amount of cooling water.

  FIG. 6 is a characteristic diagram showing how the rising speed of the cylinder wall temperature changes in accordance with the amount of engine coolant in the low temperature region. Here, the normal amount of cooling water corresponds to, for example, the amount of cooling water when cylinder wall temperature control is not executed. As in the example shown in this figure, when the amount of engine coolant is reduced, the time required for the cylinder wall temperature t to reach the temperature lower limit value t1 is shortened from T1 'to T1. For this reason, in the low temperature region, the cylinder wall temperature t can be quickly raised to fall within the pre-ignition suppression temperature region.

  On the other hand, when the cylinder wall temperature t is in a high temperature region higher than the temperature upper limit value t2, the cooling water amount variable mechanism 38 is controlled to increase the engine cooling water amount from the normal cooling water amount. Thereby, the cooling efficiency of the engine can be increased, and the cylinder wall temperature t can be lowered to fall within the pre-ignition suppression temperature region. Therefore, according to the cylinder wall temperature control, when the actual operation region of the engine enters the pre-ignition frequent operation region A, the cylinder wall temperature t deviates from the pre-ignition suppression temperature region to either the low temperature side or the high temperature side. Even so, the cylinder wall temperature t can be shifted to the suppression temperature region by the cooling water amount varying mechanism 38.

  Thus, according to the present embodiment, in the pre-ignition frequent operation region A, the cylinder wall temperature t is appropriately set based on the target temperature region (pre-ignition suppression temperature region) in which the occurrence frequency of pre-ignition is reflected. It is possible to control and suppress the occurrence of pre-ignition. That is, the pre-ignition suppression effect can be obtained only by controlling the temperature of the cylinder wall temperature t without actually generating pre-ignition or installing a means for detecting this. Therefore, the pre-ignition detection means can be omitted, and damage to the engine caused by the occurrence of pre-ignition can be minimized. Thereby, the engine can be protected from pre-ignition while simplifying the engine control system and the sensor system.

  In the present embodiment, the cylinder wall temperature t is acquired based on the engine water temperature tw without using a special temperature detection device or the like that detects the cylinder wall temperature t, and the cylinder wall is obtained via the engine water temperature tw. The temperature t can be easily controlled. Specifically, using the characteristic data shown in FIG. 5, the temperature lower limit value t1 and the temperature upper limit value t2 of the cylinder wall temperature shown in FIGS. 4 and 6 are changed to the temperature lower limit value tw1 and the temperature upper limit value tw2 of the engine water temperature. Is converted in advance. According to this configuration, in the cylinder wall temperature control, it is possible to obtain the same operational effects as described above by controlling the engine water temperature tw to fall within the pre-ignition suppression temperature region (tw1 ≦ tw ≦ tw2).

  As described above, when the engine water temperature tw is used as a control parameter, the existing water temperature sensor 44 can be used, and no special cylinder wall temperature detection means is required. Therefore, the sensor system is simplified and cost reduction is promoted. can do. In addition, in the following description, the case where the cylinder wall temperature t calculated | required from engine water temperature tw was controlled including other embodiment was illustrated. However, even in these cases, the cylinder wall temperature t1, t2, etc. may be converted into the engine water temperature tw1, tw2 in advance to control the engine water temperature tw.

(Pre-ignition suppression control)
As described above, the cylinder wall surface control can effectively suppress pre-ignition. However, in the present embodiment, the pre-ignition suppression control may be executed in order to increase the pre-ignition suppression effect in a state where the cylinder wall temperature t deviates from the pre-ignition suppression temperature region. As the preignition suppression control, known control such as air-fuel ratio enrichment control or torque down (output down) control is used. For example, the air-fuel ratio enrichment control uses the latent heat of vaporization of the fuel to reduce the in-cylinder temperature and suppress the occurrence of pre-ignition.

  FIG. 7 is an explanatory diagram illustrating an execution region of pre-ignition suppression control. The pre-ignition suppression control is performed when the cylinder wall temperature t deviates from the pre-ignition suppression temperature region in a state where the actual operation region of the engine enters the pre-ignition frequent operation region A (that is, in the low temperature region and the high temperature region described above). Is executed). And in preignition suppression control, the driving | running state (operation parameter) of an engine is changed and generation | occurrence | production of preignition is suppressed. Examples of such operating parameters include ignition timing, fuel injection amount and injection timing, ignition timing, intake air amount, intake valve or exhaust valve timing, and the like. Further, the pre-ignition suppression control is executed during a period from when the actual operation region of the engine enters the pre-ignition frequent operation region A until the cylinder wall temperature t is within the pre-ignition suppression temperature region by the cylinder wall temperature control. The cylinder wall temperature t is stopped when it falls within the pre-ignition suppression temperature region.

  As described above, the pre-ignition suppression control is executed in both the low temperature region and the high temperature region. Thus, for example, when the cylinder wall temperature t is in the low temperature range from when the engine is cold started to when the warm-up is completed, the cylinder wall temperature is quickly increased by the cylinder wall temperature control. However, the occurrence of pre-ignition can be suppressed by the pre-ignition suppression control. Even when the cylinder wall temperature t is in the high temperature region due to high output operation, high temperature environment, or the like, the effect of suppressing pre-ignition can be obtained in substantially the same manner as in the low temperature region. Accordingly, the pre-ignition can be more reliably suppressed by the synergistic effect of the cylinder wall temperature control and the pre-ignition suppression control.

  Here, the practical maximum value of the cylinder wall temperature t may be determined mainly by factors such as the structural characteristics of the engine (for example, the positional relationship between the cylinder and the cooling water channel, the cooling performance of the radiator) and the ambient temperature environment. Many. Further, the temperature upper limit value t2 in the pre-ignition suppression temperature region also tends to be determined mainly by engine structural factors. Therefore, depending on these factors, it may be difficult to reduce the temperature upper limit value t2 that has entered the high temperature region only by the cylinder wall temperature control using the cooling water amount. In this case, for example, the engine structure and the like are appropriately designed in advance so that the maximum value of the cylinder wall temperature does not enter the high temperature region (or the state in which the cylinder wall temperature enters the temporary region is temporary). Is preferred. With this configuration, the cylinder wall temperature is unlikely to enter the high temperature region. Therefore, only the preignition suppression control may be performed in the high temperature region without executing the cylinder wall temperature control. Thereby, substantially the same operation effect as this embodiment can be obtained.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 8 is a flowchart showing the control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the engine. In the routine shown in FIG. 8, first, in step 100, it is determined whether or not the actual operation region of the engine is in the pre-ignition frequent operation region A based on, for example, the engine speed and the load factor (torque). More specifically, in step 100, when the engine speed is equal to or lower than a predetermined low-rotation determination value and the load is equal to or higher than a predetermined high-load determination value, the vehicle operates in the pre-ignition frequent operation region A. Judge that it is.

  Next, in steps 102 and 104, first, the cylinder wall temperature t is calculated based on the engine water temperature, and then the pre-ignition suppression temperature region storage data (stored in advance in the ECU 50 in accordance with the pre-ignition occurrence frequency ( It is determined whether or not the cylinder wall temperature t belongs to the temperature lower limit value t1 and the temperature upper limit value t2). More specifically, in step 102, it is determined whether the cylinder wall temperature t is equal to or higher than the temperature lower limit value t1, and if this determination is not established, it is estimated that the occurrence frequency of pre-ignition exceeds the allowable limit. To do. Therefore, in this case, the above-described preignition suppression control is executed in step 106. In step 108, the cooling water amount variable mechanism 38 reduces the amount of cooling water circulating through the engine, and quickly raises the cylinder wall temperature t.

  On the other hand, even if the determination in step 102 is satisfied, if the determination in step 104 is not satisfied, the cylinder wall temperature t is higher than the temperature upper limit value t2, so that it is determined that pre-ignition is likely to occur, and step 110 , Pre-ignition suppression control is executed. In this case as well, the cylinder wall temperature control for increasing the amount of cooling water circulating through the engine by the cooling water amount varying mechanism 38 and decreasing the cylinder wall temperature t may be executed. Further, when both steps 102 and 104 are established, the cylinder wall temperature t is in the pre-ignition suppression temperature region, so it is determined that the wall temperature is appropriately controlled, and the control is terminated. .

  In the first embodiment, the pre-ignition suppression control and the cylinder wall surface control are selectively used according to the suppression temperature region in which pre-ignition is likely to occur and other temperature regions. However, the present invention is not limited to this. For example, the operation region is classified into a plurality of three or more regions according to the ease of occurrence of pre-ignition, and the execution degree of pre-ignition suppression control and cylinders are classified according to each region. You may finely control the flow volume of the cooling water by wall surface control.

  In the first embodiment, the engine water temperature has been described as an example of the temperature parameter corresponding to the cylinder wall temperature (bore wall temperature). In this case, it is not necessary to mount a device for directly detecting the cylinder wall temperature, and the system configuration can be simplified. However, the present invention is not limited to this. That is, in the present invention, the wall temperature of the cylinder or cylinder block may be directly detected, or the temperature of the lubricating oil may be used as a temperature parameter.

  In the first embodiment, the pre-ignition frequent operation region A has been described by paying attention to the tendency that pre-ignition is particularly likely to occur in the low-rotation and high-load region of the supercharged engine 10. However, the present invention is not limited to this, and in an engine or the like employing another system, if there is a tendency for pre-ignition to occur later in a specific operation region, the cylinder wall is based on the occurrence frequency of the pre-ignition in that operation region. The structure which controls temperature is also included.

  Further, in the first embodiment, in the flowchart shown in FIG. 8, the case where the cylinder wall temperature control for reducing the cooling water amount of the engine is executed only when the cylinder wall temperature t is low (less than the temperature lower limit value t1). did. However, the present invention is not limited to this, and even when the cylinder wall temperature t is high (temperature upper limit value t2 or more), for example, immediately after step 110 in FIG. Control may be performed.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, in addition to the same configuration and control as in the first embodiment, control for coping with a change in fuel properties is performed. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
As described above, the relationship between the cylinder wall temperature at a low temperature and the occurrence frequency of pre-ignition is greatly influenced by the occurrence of fuel dilution (fuel volatilization characteristics). That is, the characteristic lines shown in FIG. 4 (temperature lower limit value t1 and temperature upper limit value t2) are obtained based on a certain reference state as in, for example, gasoline (the alcohol concentration in fuel is zero). Therefore, depending on the fuel properties (heaviness and lightness of the fuel, alcohol concentration in the fuel, amount of impurities, etc.), the characteristic line in FIG. 4 may change, and the cylinder wall temperature may not be properly controlled. is there.

  Therefore, in the present embodiment, the pre-ignition occurrence frequency in the pre-ignition suppression temperature region (particularly, the temperature lower limit value t1 and the temperature upper limit value t2) is detected. When the occurrence frequency exceeds the criterion (practical allowable limit) C, the pre-ignition suppression temperature region is moved, and control is performed so that the cylinder temperature t falls within the pre-ignition suppression temperature region. Specifically, FIG. 9 is a characteristic diagram showing a case where the pre-ignition suppression temperature region is shifted to the high temperature side due to a change in fuel properties or the like in the second embodiment of the present invention. In this figure, the characteristic line (1) indicates the frequency of occurrence of pre-ignition when a constant fuel serving as a reference (for example, a fuel whose alcohol concentration in the fuel is a reference value) is used (base state). It is a characteristic diagram which shows the relationship between a cylinder wall temperature. On the other hand, the characteristic line (2) shows a state in which the pre-ignition suppression temperature region is changed to a high temperature side because the alcohol concentration is higher than that in the base state, for example.

  When the pre-ignition occurrence frequency characteristic changes as indicated by the characteristic line (2), the occurrence frequency exceeds the criterion C even if the cylinder temperature t is controlled to the appropriate temperature value (temperature lower limit value t1). become. In particular, the situation where the pre-ignition occurrence frequency exceeds the criterion C at the temperature lower limit t1 is likely to occur during a transient operation that immediately enters the pre-ignition frequent operation region A from the cold start (during low temperature start). For this reason, in the temperature region correction control, the pre-ignition suppression temperature region is corrected based on the relationship between the occurrence frequency of the pre-ignition and the cylinder wall temperature t, and the temperature region where the occurrence frequency does not exceed the criterion C (for example, t1 'To t2') are set as a new pre-ignition suppression temperature region.

  More specifically, when the pre-ignition occurrence frequency exceeds the criterion C at the temperature lower limit value t1, the temperature lower limit value t1 is shifted in the direction in which the occurrence frequency decreases (high temperature side). In addition, in the said description, the case where the generation frequency in the temperature lower limit t1 and the temperature upper limit t2 exceeded the criteria C was illustrated. However, in the temperature region correction control, when the occurrence frequency exceeds the criterion C at any temperature in the pre-ignition suppression temperature region, the pre-condition is set so that at least the occurrence frequency at the temperature is equal to or lower than the criterion C. The ignition suppression temperature region may be shifted to the high temperature side or the low temperature side. Further, the relationship between the occurrence frequency of pre-ignition and the cylinder wall temperature t may be stored in advance in the ECU 50 as a plurality of data different for each fuel property.

  On the other hand, FIG. 10 is a characteristic diagram showing a case where the pre-ignition suppression temperature region is shifted to a low temperature side due to a change in fuel properties or the like in the second embodiment of the present invention. In this figure, the characteristic line (3) shows a state in which the pre-ignition suppression temperature region has changed to the low temperature side, for example, because the alcohol concentration in the fuel is lower than the characteristic line (1) described above. In this case, the occurrence frequency exceeds the criterion C even if the cylinder temperature t is controlled to the appropriate temperature value (temperature upper limit value t2). For this reason, in the temperature region correction control, the pre-ignition suppression temperature region is corrected based on the relationship between the occurrence frequency of the pre-ignition and the cylinder wall temperature t, and the temperature region where the occurrence frequency does not exceed the criterion C (for example, t1 "~ T2") is set as a new pre-ignition suppression temperature region.

  Note that the control operation described with reference to FIG. 10 is executed even when the occurrence frequency of pre-ignition at the temperature lower limit t1 has a margin with respect to the criterion C, that is, when the occurrence frequency at low temperature is smaller than the criterion C. Is done. In this case, it is determined that the occurrence frequency of pre-ignition is not a problem even in a lower temperature region, and the temperature lower limit value t1 and the temperature upper limit value t2 are shifted to the lower temperature side. Further, after the temperature region correction control is executed, the cylinder wall temperature control described above is executed, and the actual cylinder wall temperature t is corrected to the pre-ignition suppression temperature region (for example, t1 ′ to t2 ′ or t1 ″ to The cylinder wall temperature t is controlled so as to be within t2 ″).

(Pre-ignition detection means)
Here, pre-ignition detection means will be described. As means for detecting the occurrence of pre-ignition, for example, an in-cylinder pressure sensor (CPS) and a knock sensor (KCS) are known. As shown in FIG. 3, the CPS performs a detection operation using the fact that the maximum in-cylinder pressure Pmax becomes extremely large when pre-ignition occurs. Further, as shown in FIG. 3, the KCS performs a detection operation by utilizing the generation of a specific frequency component when pre-ignition occurs. Furthermore, there is also known a method for detecting the occurrence of pre-ignition based on the behavior of the ion current by utilizing the fact that an ion current flows between the electrodes of the spark plug when pre-ignition occurs.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 11 is a flowchart showing the control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the engine. In FIG. 11, first, in step 200, it is determined whether or not the actual operation region of the engine is in the pre-ignition frequent operation region A, and in step 202, the occurrence frequency of pre-ignition is measured. In step 204, the temperature region correction control is executed, and the pre-ignition suppression temperature region is corrected based on the change in the pre-ignition occurrence frequency with respect to the base state. A method for measuring the occurrence frequency of pre-ignition will be described later. Next, in steps 206 to 216, processing similar to that in steps 102 to 110 of the first embodiment (FIG. 8) is executed, and cylinder wall temperature control and preignition suppression control are executed as necessary.

  In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment. In particular, according to the temperature region correction control, for example, the pre-ignition suppression temperature region (t1 ≦ t ≦ t2) in the base state (before correction) is optimal due to, for example, a change in fuel properties or a change over time in the occurrence frequency of pre-ignition. Even if it is deviated from this region, the corrected temperature region (t1 ′ ≦ t ≦ t2 ′) can be adjusted to the optimum region based on the actual occurrence frequency of pre-ignition. That is, even when an appropriate temperature region that minimizes the occurrence of pre-ignition varies due to an external factor, the temperature lower limit value t1 and the temperature upper limit value t2 can be corrected to appropriate temperatures. Therefore, it is possible to absorb the influence due to the change in the fuel property, the deterioration with time of the equipment, etc. by the temperature region correction control and appropriately execute the cylinder wall temperature control. Moreover, the temperature region correction control can be executed using only the pre-ignition occurrence frequency as a parameter without using a special mechanism or sensor for detecting changes in fuel properties or engine characteristics over time. It is possible to simplify cost and promote cost reduction.

The t2_max described in FIG . 9 and FIG. 10 exemplifies the maximum possible temperature of the cylinder wall temperature limited by the structure of the engine or the like. In the second embodiment, when the temperature lower limit value t1 and the temperature upper limit value t2 are changed (shifted) by the temperature region correction control, both shift amounts may be set equal or different from each other.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that, in the same configuration and control as in the first embodiment, only the temperature lower limit value in the pre-ignition suppression temperature region is made variable. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
The temperature upper limit value t2 in the pre-ignition suppression temperature region is preferably originally set based on the occurrence frequency of pre-ignition. However, it may be difficult to shift the cylinder wall temperature t to a higher temperature side than the temperature upper limit value t2 depending on the structural characteristics of the engine and the surrounding temperature environment (heat resistance, etc.). Therefore, in the present embodiment, control corresponding to such a case will be described. FIG. 12 is a characteristic diagram showing a case where the pre-ignition suppression temperature region is shifted to a low temperature side due to a change in fuel properties or the like in the third embodiment of the present invention. In the present embodiment, when the occurrence frequency of pre-ignition in the pre-ignition suppression temperature region exceeds the criterion C, only the temperature lower limit value t1 is shifted to the high temperature side or the low temperature side. This shift operation is executed by the cooling water amount variable mechanism 38 and is the same as that of the second embodiment. Further, when the cylinder wall temperature t deviates from the pre-ignition suppression temperature region A to the low temperature side and the high temperature side, the above-described pre-ignition suppression control is executed.

  On the other hand, the temperature upper limit value t2 is held at the above-mentioned maximum temperature t2_max regardless of whether the occurrence frequency exceeds the criterion C or not. That is, t2 ′ and t2 ″ in the second embodiment are set equal to the maximum temperature t2_max. The maximum temperature t2_max, which is the criteria temperature of the cylinder wall temperature, is determined by the occurrence frequency of pre-ignition at the temperature as the criterion C. This setting is realized, for example, by devising a hardware configuration such as an engine cooling system, etc. In order to specifically realize the control of the third embodiment, In Step 204 of FIG. 2 (FIG. 11), only the temperature lower limit value t1 may be changed and the temperature upper limit value may be held at t2_max. It is possible to obtain substantially the same operational effects as in Embodiment 1. In particular, in the present embodiment, it is possible to appropriately control the cylinder wall temperature according to the hardware configuration of the engine. Kill.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that, in the same configuration and control as in the first embodiment, the relationship between the pre-ignition occurrence frequency and the cylinder wall temperature is learned based on changes in fuel properties and the environment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 4]
In the learning control, when the occurrence frequency of pre-ignition is detected and the temperature lower limit value t1 and the temperature upper limit value t2 are changed, the relationship between the occurrence frequency and the temperature region is learned. As a specific example, first, it is assumed that the cylinder temperature t is realized with a specific cooling water amount w in a preset base state. Here, when the occurrence frequency of pre-ignition increases due to, for example, a change in fuel properties, the amount of cooling water is decreased by cylinder wall temperature control to increase the cylinder wall temperature, and the occurrence frequency is decreased. When the pre-ignition occurrence frequency decreases to the criterion C or lower, the cylinder wall temperature at that time (the relationship between the cylinder wall temperature and the pre-ignition occurrence frequency) is learned. And the result of this learning control is memorize | stored in ECU50 by updating the memory | storage data of the characteristic line shown, for example in FIG.4, FIG.9, FIG.10.

[Specific processing for realizing Embodiment 4]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 13 is a flowchart showing the control executed by the ECU in the fourth embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the engine. The routine shown in Figures 1 to 3 is obtained by adding a learning control in step 300 and 302 to a routine of the second embodiment (FIG. 11).

  In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first to third embodiments. In this embodiment, by performing learning control, it is possible to flexibly cope with, for example, changes in fuel properties and changes with time of the engine. Even if these changes occur, the cylinder wall temperature is appropriately set. Control can suppress the occurrence of pre-ignition.

Embodiment 5. FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, in the same configuration and control as in the first embodiment, when preignition suppression control is executed, the control start time is delayed according to the cylinder wall temperature. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 14 is an explanatory diagram showing how the cylinder wall temperature t rises from a low temperature region to a preignition suppression temperature region by cold starting the engine in the fifth embodiment of the present invention. As described above, in the pre-ignition frequent operation region A, the cylinder wall surface control for reducing the cooling water amount of the engine during the time (0 to Ta to Tb) until the wall surface temperature t reaches the temperature lower limit value t1. Pre-ignition suppression control is executed by A / F enrichment, torque reduction, or the like. However, since the preignition suppression control changes the operating state of the internal combustion engine and easily affects the drivability and exhaust emission, it is preferable to avoid long-time execution.

  Therefore, in the present embodiment, when the pre-ignition suppression control is activated for the first time after the engine is cold-started, the cylinder wall temperature t (hereinafter referred to as the actual operation region enters the pre-ignition frequent operation region A). As the cylinder wall temperature t at the time of entry increases), the control (the suppression delay control) for delaying the start timing Ta of the preignition suppression control is executed. FIG. 15 is a characteristic diagram for setting the delay time ta of the pre-ignition suppression control from the cylinder wall temperature t at the time of entry. This characteristic diagram is stored in the ECU 50 in advance. As shown in FIG. 15, the delay time ta (= corresponding to the disclosure timing Ta of the control) from when the actual operation region enters the pre-ignition frequent operation region A to when the pre-ignition suppression control is started is The cylinder wall temperature t at the time of entry is set in advance so as to increase as the cylinder wall temperature t increases. This setting is due to the following reason.

  First, the premise will be described. In the low temperature region, the fuel is basically difficult to evaporate, so the oil dilution rate tends to increase, and pre-ignition is likely to occur. However, in the low temperature region, since the in-cylinder temperature is low, it is difficult to ignite even if there is a fire type due to scattered oil droplets, so the occurrence frequency of pre-ignition is determined according to the balance between the two. Therefore, when the balance between the two is lost due to an increase in the cylinder wall temperature (in-cylinder temperature) or the like, the frequency of occurrence of pre-ignition suddenly increases from a certain temperature.

  On the other hand, when the cylinder wall temperature is lower than the temperature lower limit value T1, preignition suppression is executed. As described above, the preignition suppression control affects the drivability of the vehicle. However, even in the low temperature region, if the cylinder wall temperature is close to the pre-ignition suppression temperature region (temperature lower limit value t1), the engine often does not necessarily require pre-ignition suppression control. This is because in the vicinity of the pre-ignition suppression temperature region, the pre-ignition occurrence frequency decreases as shown in FIG.

  For this reason, in the suppression delay control, the start timing Ta of the pre-ignition suppression control is increased as the cylinder wall temperature t at the time of entry is higher in the low temperature region, that is, as the cylinder wall temperature t at the time of entry is closer to the pre-ignition suppression temperature region. To reduce the execution time. That is, in the low temperature region, the pre-ignition is less likely to occur as the cylinder wall temperature t is higher. Therefore, the control standby time ta is lengthened so that the pre-ignition suppression control is not performed as much as possible. On the other hand, in the suppression delay control, as the cylinder wall temperature t at the time of entry is lower in the low temperature region, the start timing Ta of the pre-ignition suppression control is advanced and the execution time is lengthened. That is, in this case, since the pre-ignition is likely to occur when the pre-ignition frequent operation region A is entered, the pre-ignition suppression control is executed as early as possible.

  In the present embodiment configured as described above, substantially the same operational effects as those of the first embodiment can be obtained. In particular, in the suppression delay control, the start timing of the pre-ignition suppression control can be delayed according to the cylinder wall temperature at the time of entry into the pre-ignition frequent operation region A, so that the engine is generated while suppressing the occurrence frequency of the pre-ignition. Operability and exhaust emissions can be ensured.

[Specific Processing for Realizing Embodiment 5]
Next, a specific process for realizing the above-described control will be described with reference to FIG. FIG. 16 is a flowchart showing control executed by the ECU in the fifth embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the engine. In the routine shown in FIG. 16, first, in step 400, it is determined whether or not the actual operation region is within the pre-ignition frequent operation region A. If this determination is not established, this routine is terminated as it is. Further, when the determination in step 400 is established, in step 402, the cylinder wall temperature t at the time of entry, which is the cylinder wall temperature when entering the operation region A, is acquired. In step 404, for example, based on the characteristic line of FIG. The delay time ta is calculated from the cylinder wall temperature t at the time of entry.

  Next, in step 406, it is determined whether or not the cylinder wall temperature t is in the low temperature region, as in the first embodiment (FIG. 8). In the case of the low temperature region, in step 408, the above cylinder wall temperature control is executed. In step 410, it is determined whether or not a predetermined delay time ta has elapsed since entering the pre-ignition frequent operation area A, and the system waits until this time elapses. Next, in step 412, preignition suppression control is executed after the delay time ta has elapsed.

On the other hand, if the determination in step 406 is not established, it is determined in step 414 whether or not the cylinder wall temperature t is in a high temperature region. In the case of the high temperature region, it is determined in step 416 whether or not a predetermined delay time ta has elapsed since entering the frequent operation region A, and waits until this time has elapsed. Next, in step 418, preignition suppression control is executed. If both steps 406 and 414 are established, the cylinder wall temperature t is in the pre-ignition suppression temperature region, so it is determined that the wall temperature is appropriately controlled, and the control ends. .

Embodiment 6 FIG.
Next, a sixth embodiment of the present invention will be described with reference to FIG. In the present embodiment, in the control of the fifth embodiment, the relationship between the cylinder wall temperature at the time of entry and the delay time of the preignition suppression control is learned. In the present embodiment, the same components as those in the fifth embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 17 is an explanatory diagram showing correction control for correcting the relationship between the cylinder wall temperature t at the time of entry and the delay time ta of pre-ignition suppression control in the sixth embodiment of the present invention. As shown in this figure, in the present embodiment, delay correction control for updating the characteristic data representing the relationship between the cylinder wall temperature t at the time of entry and the delay time ta is executed based on the pre-ignition occurrence state. . In the delay correction control, for example, when pre-ignition occurs before the start of the pre-ignition suppression control, the relationship between the cylinder wall temperature t at the time of entry and the delay time ta is fixed as shown in an example of FIG. The delay time ta is corrected with respect to the cylinder wall temperature t so that the control start time Ta is shortened. Then, the correction result (corrected characteristic line) is stored as a learning result.

In the present embodiment configured as described above, substantially the same operational effects as those of the first and sixth embodiments can be obtained. In particular, in the present embodiment, it is possible to learn the relationship between the cylinder wall temperature t at the time of entry caused by a change with time of the engine and the like and the delay time ta based on the pre-ignition occurrence state .

10 Engine (Internal combustion engine)
12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Intercooler 26 Exhaust purification catalyst 28 Fuel injection valve 30 Spark plug 32 Intake valve 34 Exhaust valve 36 Turbocharger 38 Cooling water amount variable mechanism (cylinder wall) Variable temperature means)
40 Crank angle sensor 42 Air flow sensor 44 Water temperature sensor (wall temperature parameter acquisition means)
46 In-cylinder pressure sensor (pre-ignition detection means)
50 ECU (pre-ignition temperature region storage means)
A Preignition frequent operation area t Cylinder wall temperature tw Engine water temperature (wall temperature parameter)
t1, t1 ', t1 "Temperature lower limit t2, t2', 21" Temperature upper limit ta Delay time

Claims (5)

In a control device applied to a supercharged internal combustion engine having a fuel injection valve, a spark plug, and a supercharger,
Wall temperature parameter acquisition means for acquiring a cylinder wall temperature of an internal combustion engine or a parameter corresponding to the cylinder wall temperature as a wall temperature parameter;
Pre-ignition suppression means for performing pre-ignition suppression control for reducing the in-cylinder temperature in order to suppress pre-ignition that occurs before ignition by the spark plug, and
The pre-ignition suppression means is in engine operation in a predetermined low-rotation high-load region between the start of the internal combustion engine and the completion of warm-up , and the occurrence frequency of the pre-ignition and the wall temperature parameter the wall temperature parameters than the temperature lower limit value of the temperature region in which the frequency is equal to or less than the allowable limit in the relationship of the case small again, the control device for an internal combustion engine with a supercharger for performing the pre-ignition suppression control.   2. The control device for an internal combustion engine with a supercharger according to claim 1, wherein the preignition suppression control reduces the in-cylinder temperature by performing an increase correction of a fuel injection amount by the fuel injection valve. The internal combustion engine with a supercharger includes an intake valve and an exhaust valve,
2. The control device for an internal combustion engine with a supercharger according to claim 1, wherein the preignition suppression control reduces the in-cylinder temperature by controlling a valve timing of the intake valve or the exhaust valve. In a control method applied to a supercharged internal combustion engine comprising a fuel injection valve, a spark plug and a supercharger,
Obtaining a cylinder wall temperature of the internal combustion engine or a parameter corresponding to the cylinder wall temperature as a wall temperature parameter;
The engine is operating in a predetermined low rotation and high load region from the start of the internal combustion engine to the completion of warm-up , and the occurrence frequency is related to the occurrence frequency of pre-ignition and the wall temperature parameter. when the wall temperature parameters than the temperature lower limit value of the temperature region where the allowable limit or less small again, the pre-ignition suppression to reduce the in-cylinder temperature to suppress preignition ignition occurs before ignition by the spark plug A method for controlling an internal combustion engine with a supercharger for executing control.   5. The method of controlling an internal combustion engine with a supercharger according to claim 4, wherein the pre-ignition suppression control reduces the in-cylinder temperature by performing an increase correction of a fuel injection amount by the fuel injection valve.

Images